Merge branch 'main' into feature/parametric-constraint-system

# Conflicts:
#	src/app/automation.rs
#	src/app/mod.rs
#	src/ui/ribbon/widgets.rs

src/modules/draw/draw/arc.rs

@@ -7,7 +7,7 @@ use cadkernel::geom2d::{self, Curve as KernelCurve};
 
 use crate::command::{CadCommand, CmdResult, WorkingPlane};
 use crate::modules::IconKind;
-use crate::scene::model::wire_model::WireModel;
+use crate::scene::model::wire_model::{TangentGeom, WireModel};
 use glam::DVec3;
 
 const TAU: f64 = std::f64::consts::TAU;
@@ -71,9 +71,9 @@ fn arc_preview(
     end_angle: f64,
     plane: WorkingPlane,
 ) -> Option<WireModel> {
-    let center = plane.to_local(center);
+    let center_local = plane.to_local(center);
     let arc = geom2d::bounded_arc(
-        [center.x, center.y],
+        [center_local.x, center_local.y],
         radius,
         start_angle,
         end_angle,
@@ -81,14 +81,23 @@ fn arc_preview(
     let points = KernelCurve::Arc(arc)
         .tessellate_angle(TAU / 64.0)
         .into_iter()
-        .map(|point| plane.to_world(DVec3::new(point[0], point[1], center.z)).to_array())
+        .map(|point| plane.to_world(DVec3::new(point[0], point[1], center_local.z)).to_array())
         .collect();
-    Some(WireModel::solid_f64(
+    let mut wire = WireModel::solid_f64(
         "rubber_band".into(),
         points,
         WireModel::CYAN,
         false,
-    ))
+    );
+    wire.tangent_geoms.push(TangentGeom::Arc {
+        center: [center.x, center.y, center.z],
+        axis_x: plane.x.to_array(),
+        axis_y: plane.y.to_array(),
+        radius: arc.radius,
+        start_angle: arc.start_angle,
+        end_angle: arc.end_angle,
+    });
+    Some(wire)
 }
 
 fn make_arc(

src/modules/draw/draw/circle.rs

@@ -11,7 +11,7 @@ use crate::t;
 use crate::command::{CadCommand, CmdResult, DynField, TangentObject, WorkingPlane};
 use crate::modules::draw::defaults;
 use crate::modules::IconKind;
-use crate::scene::model::wire_model::WireModel;
+use crate::scene::model::wire_model::{TangentGeom, WireModel};
 use glam::DVec3;
 
 const TAU: f64 = std::f64::consts::TAU;
@@ -56,16 +56,23 @@ pub const ICON: IconKind = ICON_CR;
 // ── Shared geometry ────────────────────────────────────────────────────────
 
 fn circle_wire(center: DVec3, radius: f64, plane: WorkingPlane) -> WireModel {
-    let center = plane.to_local(center);
+    let center_local = plane.to_local(center);
     let points = KernelCurve::Circle(KernelCircle {
-        centre: [center.x, center.y],
+        centre: [center_local.x, center_local.y],
         radius,
     })
         .tessellate_angle(TAU / 64.0)
         .into_iter()
-        .map(|point| plane.to_world(DVec3::new(point[0], point[1], center.z)).to_array())
+        .map(|point| plane.to_world(DVec3::new(point[0], point[1], center_local.z)).to_array())
         .collect();
-    WireModel::solid_f64("rubber_band".into(), points, WireModel::CYAN, false)
+    let mut wire = WireModel::solid_f64("rubber_band".into(), points, WireModel::CYAN, false);
+    wire.tangent_geoms.push(TangentGeom::PlanarCircle {
+        center: [center.x, center.y, center.z],
+        axis_x: plane.x.to_array(),
+        axis_y: plane.y.to_array(),
+        radius,
+    });
+    wire
 }
 
 fn make_circle(center: DVec3, radius: f64, plane: WorkingPlane) -> EntityType {

src/modules/draw/draw/ellipse.rs

@@ -11,7 +11,7 @@ use crate::t;
 
 use crate::command::{CadCommand, CmdResult, WorkingPlane};
 use crate::modules::IconKind;
-use crate::scene::model::wire_model::WireModel;
+use crate::scene::model::wire_model::{TangentGeom, WireModel};
 use glam::DVec3;
 
 fn parse_num(text: &str) -> Option<f64> {
@@ -75,7 +75,16 @@ fn ellipse_wire(
             [p.x, p.y, p.z]
         })
         .collect();
-    WireModel::solid_f64("rubber_band".into(), pts, WireModel::CYAN, false)
+    let mut wire = WireModel::solid_f64("rubber_band".into(), pts, WireModel::CYAN, false);
+    wire.tangent_geoms.push(TangentGeom::PlanarEllipse {
+        center: [center.x, center.y, center.z],
+        major_axis: [major.x, major.y, major.z],
+        normal: plane.z.to_array(),
+        minor_axis_ratio: ratio,
+        start_param: t_start,
+        end_param: t_e,
+    });
+    wire
 }
 
 /// Convert a world point to the parametric angle on the ellipse.

src/modules/draw/draw/polyline.rs

@@ -17,7 +17,7 @@ use crate::t;
 
 use crate::command::{CadCommand, CmdResult, WorkingPlane};
 use crate::modules::{IconKind, ModuleEvent, ToolDef};
-use crate::scene::model::wire_model::WireModel;
+use crate::scene::model::wire_model::{TangentGeom, WireModel};
 
 // ── Ribbon definition ──────────────────────────────────────────────────────
 
@@ -443,6 +443,7 @@ impl CadCommand for PlineCommand {
         let pt = self.plane.to_local(pt_world).as_vec3();
 
         let mut pts: Vec<[f32; 3]> = Vec::new();
+        let mut tangent_geom = None;
         match self.mode {
             SegMode::Line => {
                 pts.push([last.x, last.y, last.z]);
@@ -456,8 +457,44 @@ impl CadCommand for PlineCommand {
                     .map(|t| t.as_dvec2())
                     .unwrap_or(DVec2::new(1.0, 0.0));
                 let bulge = compute_bulge(a, tangent, b);
-                let arc_pts = arc_sample_points(last, bulge, pt, 16);
-                pts.extend_from_slice(&arc_pts);
+                if bulge.abs() >= 1e-9 && (b - a).length_squared() >= 1e-12 {
+                    if let Some(arc) =
+                        crate::entities::common::BulgeArc::from_bulge([a.x, a.y], [b.x, b.y], bulge)
+                    {
+                        for s in arc.tessellate_angle(std::f64::consts::TAU / 64.0) {
+                            pts.push([s[0] as f32, s[1] as f32, last.z]);
+                        }
+                        let (sa, ea) = if arc.sweep >= 0.0 {
+                            (arc.start_angle, arc.end_angle)
+                        } else {
+                            (arc.end_angle, arc.start_angle)
+                        };
+                        let world_center = self
+                            .plane
+                            .to_world(DVec3::new(arc.center[0], arc.center[1], last.z as f64));
+                        if arc.radius > 0.0
+                            && arc.radius.is_finite()
+                            && arc.radius <= 1e6
+                            && sa.is_finite()
+                            && ea.is_finite()
+                        {
+                            tangent_geom = Some(TangentGeom::Arc {
+                                center: world_center.to_array(),
+                                axis_x: self.plane.x.to_array(),
+                                axis_y: self.plane.y.to_array(),
+                                radius: arc.radius,
+                                start_angle: sa,
+                                end_angle: ea,
+                            });
+                        }
+                    } else {
+                        let arc_pts = arc_sample_points(last, bulge, pt, 64);
+                        pts.extend_from_slice(&arc_pts);
+                    }
+                } else {
+                    pts.push([last.x, last.y, last.z]);
+                    pts.push([pt.x, pt.y, pt.z]);
+                }
             }
         }
 
@@ -465,12 +502,16 @@ impl CadCommand for PlineCommand {
             .into_iter()
             .map(|point| self.plane.to_world(Vec3::from_array(point).as_dvec3()).as_vec3().to_array())
             .collect();
-        Some(WireModel::solid(
+        let mut wire = WireModel::solid(
             "rubber_band".into(),
             world_points,
             WireModel::CYAN,
             false,
-        ))
+        );
+        if let Some(tg) = tangent_geom {
+            wire.tangent_geoms.push(tg);
+        }
+        Some(wire)
     }
 }
 
@@ -548,4 +589,20 @@ mod tests {
             CmdResult::FinalizeLiveEntity(h) if h == handle
         ));
     }
+
+    #[test]
+    fn test_draw_line_then_arc() {
+        let mut cmd = PlineCommand::new();
+        cmd.on_point(DVec3::new(0.0, 0.0, 0.0));
+        let res = cmd.on_point(DVec3::new(10.0, 0.0, 0.0));
+        assert!(matches!(res, CmdResult::CommitLiveEntity(_)));
+        cmd.set_live_handle(Handle::new(1));
+        cmd.on_text_input("A");
+        let wire = cmd.on_mouse_move(DVec3::new(10.0, 5.0, 0.0)).expect("arc wire");
+        assert_eq!(wire.tangent_geoms.len(), 1);
+        assert!(matches!(wire.tangent_geoms[0], TangentGeom::Arc { .. }));
+        assert!(wire.points.len() >= 16);
+        let res2 = cmd.on_point(DVec3::new(10.0, 5.0, 0.0));
+        assert!(matches!(res2, CmdResult::UpdateLiveEntity { .. }));
+    }
 }

src/modules/draw/modify/fillet.rs

@@ -77,7 +77,122 @@ fn project_click(click: [f64; 2], p1: [f64; 2], unit: [f64; 2]) -> f64 {
 }
 
 // ── Fillet ─────────────────────────────────────────────────────────────────
+/// Fillet two parallel lines with a semicircle tangent to both.
+///
+/// The current FILLET radius is intentionally ignored for parallel lines:
+/// the effective radius is half the perpendicular distance between them.
+///
+/// The endpoint of the first line nearest its pick determines where the
+/// semicircle is placed. The second line is trimmed or extended to the
+/// corresponding perpendicular tangent point.
+fn fillet_parallel_lines(
+    l1: &LineEnt,
+    click1: [f64; 2],
+    l2: &LineEnt,
+    click2: [f64; 2],
+) -> Option<(EntityType, EntityType, Option<EntityType>)> {
+    let (p1, p2, u1, len1) = line_geom(l1);
+    let (p3, _p4, u2, len2) = line_geom(l2);
 
+    if len1 <= 1.0e-12 || len2 <= 1.0e-12 {
+        return None;
+    }
+
+    // This helper is only for parallel / anti-parallel lines.
+    let cross = u1[0] * u2[1] - u1[1] * u2[0];
+    if cross.abs() > 1.0e-6 {
+        return None;
+    }
+
+    // The pick on the first line determines which end receives the round.
+    let dist_sq = |a: [f64; 2], b: [f64; 2]| {
+        let dx = a[0] - b[0];
+        let dy = a[1] - b[1];
+        dx * dx + dy * dy
+    };
+
+    let (tangent1, other1) = if dist_sq(click1, p1) <= dist_sq(click1, p2) {
+        (p1, p2)
+    } else {
+        (p2, p1)
+    };
+
+    // Unit normal to line 1. Project tangent1 perpendicularly onto line 2.
+    let normal = [-u1[1], u1[0]];
+    let separation =
+        (p3[0] - tangent1[0]) * normal[0] + (p3[1] - tangent1[1]) * normal[1];
+
+    if separation.abs() <= 1.0e-9 {
+        // Coincident lines do not define a useful semicircle.
+        return None;
+    }
+
+    let tangent2 = [
+        tangent1[0] + normal[0] * separation,
+        tangent1[1] + normal[1] * separation,
+    ];
+
+    let centre = [
+        (tangent1[0] + tangent2[0]) * 0.5,
+        (tangent1[1] + tangent2[1]) * 0.5,
+    ];
+
+    let radius = separation.abs() * 0.5;
+
+    // Keep the existing part of each selected line and trim/extend the picked
+    // end to its tangent point.
+    let new_l1 = trim_line_to_point(l1, tangent1, click1)?;
+    let new_l2 = trim_line_to_point(l2, tangent2, click2)?;
+
+    // The semicircle must bulge away from the retained portion of line 1.
+    // `other1 - tangent1` points back into the line, so negate it.
+    let keep = [
+        other1[0] - tangent1[0],
+        other1[1] - tangent1[1],
+    ];
+    let keep_len = (keep[0] * keep[0] + keep[1] * keep[1]).sqrt();
+
+    if keep_len <= 1.0e-12 {
+        return None;
+    }
+
+    let bulge_dir = [-keep[0] / keep_len, -keep[1] / keep_len];
+
+    let a1 = norm_angle(
+        (tangent1[1] - centre[1]).atan2(tangent1[0] - centre[0]),
+    );
+    let a2 = norm_angle(
+        (tangent2[1] - centre[1]).atan2(tangent2[0] - centre[0]),
+    );
+
+    // Between two antipodal points there are two possible semicircles.
+    // Determine which CCW orientation bulges toward the selected end.
+    let midpoint_angle = a1 + std::f64::consts::FRAC_PI_2;
+    let midpoint_dir = [midpoint_angle.cos(), midpoint_angle.sin()];
+
+    let candidate_matches =
+        midpoint_dir[0] * bulge_dir[0] + midpoint_dir[1] * bulge_dir[1] >= 0.0;
+
+    let (start_angle, end_angle) = if candidate_matches {
+        (a1, a2)
+    } else {
+        (a2, a1)
+    };
+
+    let mut arc = ArcEnt::new();
+    arc.common = l1.common.clone();
+    arc.common.handle = Handle::NULL;
+    arc.center = Vector3::new(centre[0], centre[1], l1.start.z);
+    arc.radius = radius;
+    arc.start_angle = start_angle;
+    arc.end_angle = end_angle;
+
+    Some((
+        EntityType::Line(new_l1),
+        EntityType::Line(new_l2),
+        Some(EntityType::Arc(arc)),
+    ))
+}
 /// Compute fillet: trim l1/l2 and insert a tangent arc of `radius`.
 /// Returns (trimmed_l1, trimmed_l2, fillet_arc).
 fn compute_fillet(
@@ -90,8 +205,18 @@ fn compute_fillet(
     let (p1, p2, u1, _len1) = line_geom(l1);
     let (p3, p4, u2, _len2) = line_geom(l2);
 
-    // Intersection of infinite lines
-    let (t_p, _u_p) = ll(p1[0], p1[1], u1[0], u1[1], p3[0], p3[1], u2[0], u2[1])?;
+    // Parallel lines are a special FILLET case: there is no intersection.
+    // Build the tangent semicircle directly, temporarily ignoring the
+    // configured radius.
+    let cross = u1[0] * u2[1] - u1[1] * u2[0];
+
+    if cross.abs() <= 1.0e-6 {
+        return fillet_parallel_lines(l1, click1, l2, click2);
+    }
+
+    // Intersection of infinite non-parallel lines.
+    let (t_p, _u_p) =
+        ll(p1[0], p1[1], u1[0], u1[1], p3[0], p3[1], u2[0], u2[1])?;
 
     // Intersection point
     let px = p1[0] + t_p * u1[0];
@@ -123,14 +248,6 @@ fn compute_fillet(
         [-u2[0], -u2[1]]
     };
 
-    // Angle between the two keep-directions
-    let cos_a = (dir1[0] * dir2[0] + dir1[1] * dir2[1]).clamp(-1.0, 1.0);
-    let angle = cos_a.acos();
-
-    // Lines are parallel / anti-parallel
-    if angle < 1e-6 || (angle - std::f64::consts::PI).abs() < 1e-6 {
-        return None;
-    }
 
     let z = l1.start.z;
 
@@ -337,7 +454,194 @@ fn compute_bulge(t1: [f64; 2], t2: [f64; 2], arc_center: [f64; 2]) -> f64 {
         -(span_cw / 4.0).tan() // CW arc
     }
 }
+#[derive(Clone, Copy)]
+struct PolylineCornerFillet {
+    incoming: [f64; 2],
+    outgoing: [f64; 2],
+    bulge: f64,
+}
 
+fn segment_parameter(point: [f64; 2], start: [f64; 2], end: [f64; 2]) -> Option<f64> {
+    let dx = end[0] - start[0];
+    let dy = end[1] - start[1];
+    let len2 = dx * dx + dy * dy;
+
+    if len2 <= 1.0e-20 {
+        return None;
+    }
+
+    Some(
+        ((point[0] - start[0]) * dx + (point[1] - start[1]) * dy) / len2,
+    )
+}
+
+/// Apply the current FILLET radius to every eligible corner of a 2D polyline.
+///
+/// Initial scope deliberately handles straight-segment corners only. Corners
+/// adjacent to an existing bulge arc are preserved unchanged.
+fn fillet_entire_lwpolyline(poly: &LwPolyline, radius: f64) -> Option<LwPolyline> {
+    let n = poly.vertices.len();
+
+    if n < 3 || radius <= 1.0e-9 {
+        return None;
+    }
+
+    let mut corners: Vec<Option<PolylineCornerFillet>> = vec![None; n];
+
+    let first_corner = if poly.is_closed { 0 } else { 1 };
+    let end_corner = if poly.is_closed {
+        n
+    } else {
+        n.saturating_sub(1)
+    };
+
+    for i in first_corner..end_corner {
+        let prev = if i == 0 { n - 1 } else { i - 1 };
+
+        // A bulge belongs to the segment starting at that vertex.
+        // For now only fillet corners where both adjacent segments are straight.
+        if poly.vertices[prev].bulge.abs() >= 1.0e-9
+            || poly.vertices[i].bulge.abs() >= 1.0e-9
+        {
+            continue;
+        }
+
+        let incoming = lwpoly_seg_as_line(poly, prev);
+        let outgoing = lwpoly_seg_as_line(poly, i);
+
+        // Pick points halfway along each segment, away from the corner.
+        // This tells the existing line-line FILLET code which side to keep.
+        let click_in = [
+            (incoming.start.x + incoming.end.x) * 0.5,
+            (incoming.start.y + incoming.end.y) * 0.5,
+        ];
+        let click_out = [
+            (outgoing.start.x + outgoing.end.x) * 0.5,
+            (outgoing.start.y + outgoing.end.y) * 0.5,
+        ];
+
+        let Some((trimmed_in, trimmed_out, maybe_arc)) =
+            compute_fillet(&incoming, click_in, &outgoing, click_out, radius)
+        else {
+            continue;
+        };
+
+        let (
+            EntityType::Line(trimmed_in),
+            EntityType::Line(trimmed_out),
+            Some(EntityType::Arc(arc)),
+        ) = (trimmed_in, trimmed_out, maybe_arc)
+        else {
+            continue;
+        };
+
+        let tangent_in = [trimmed_in.end.x, trimmed_in.end.y];
+        let tangent_out = [trimmed_out.start.x, trimmed_out.start.y];
+
+        let in_start = [incoming.start.x, incoming.start.y];
+        let in_end = [incoming.end.x, incoming.end.y];
+        let out_start = [outgoing.start.x, outgoing.start.y];
+        let out_end = [outgoing.end.x, outgoing.end.y];
+
+        let Some(t_in) = segment_parameter(tangent_in, in_start, in_end) else {
+            continue;
+        };
+        let Some(t_out) = segment_parameter(tangent_out, out_start, out_end) else {
+            continue;
+        };
+
+        // Whole-polyline FILLET should not extend past neighbouring vertices.
+        // If this radius cannot fit at this corner, leave that corner unchanged.
+        if !(-1.0e-9..=1.0 + 1.0e-9).contains(&t_in)
+            || !(-1.0e-9..=1.0 + 1.0e-9).contains(&t_out)
+        {
+            continue;
+        }
+
+        corners[i] = Some(PolylineCornerFillet {
+            incoming: tangent_in,
+            outgoing: tangent_out,
+            bulge: compute_bulge(
+                tangent_in,
+                tangent_out,
+                [arc.center.x, arc.center.y],
+            ),
+        });
+    }
+
+    if corners.iter().all(Option::is_none) {
+        return None;
+    }
+
+    // Adjacent fillets must not consume more than the shared segment.
+    // Reject the operation rather than producing an inverted/overlapping edge.
+    let segment_count = if poly.is_closed { n } else { n - 1 };
+
+    for i in 0..segment_count {
+        let next = (i + 1) % n;
+
+        let start = corners[i]
+            .map(|corner| corner.outgoing)
+            .unwrap_or([
+                poly.vertices[i].location.x,
+                poly.vertices[i].location.y,
+            ]);
+
+        let end = corners[next]
+            .map(|corner| corner.incoming)
+            .unwrap_or([
+                poly.vertices[next].location.x,
+                poly.vertices[next].location.y,
+            ]);
+
+        let original_start = [
+            poly.vertices[i].location.x,
+            poly.vertices[i].location.y,
+        ];
+        let original_end = [
+            poly.vertices[next].location.x,
+            poly.vertices[next].location.y,
+        ];
+
+        let Some(start_t) = segment_parameter(start, original_start, original_end) else {
+            continue;
+        };
+        let Some(end_t) = segment_parameter(end, original_start, original_end) else {
+            continue;
+        };
+
+        if start_t > end_t + 1.0e-9 {
+            return None;
+        }
+    }
+
+    let mut result = poly.clone();
+    result.common.handle = Handle::NULL;
+    result.vertices.clear();
+
+    for (i, original) in poly.vertices.iter().enumerate() {
+        if let Some(corner) = corners[i] {
+            let mut tangent_in = original.clone();
+            tangent_in.location.x = corner.incoming[0];
+            tangent_in.location.y = corner.incoming[1];
+            tangent_in.bulge = corner.bulge;
+
+            let mut tangent_out = original.clone();
+            tangent_out.location.x = corner.outgoing[0];
+            tangent_out.location.y = corner.outgoing[1];
+
+            // This corner is only eligible when its outgoing segment is straight.
+            tangent_out.bulge = 0.0;
+
+            result.vertices.push(tangent_in);
+            result.vertices.push(tangent_out);
+        } else {
+            result.vertices.push(original.clone());
+        }
+    }
+
+    Some(result)
+}
 /// Rebuild a LwPolyline, replacing the corner vertex at `corner_idx` with two
 /// new vertices T1 (start of fillet arc) and T2 (end of fillet arc).
 /// `bulge` encodes the direction and span of the arc (T1 → T2).
@@ -991,6 +1295,7 @@ fn compute_chamfer(
 
 enum FilletStep {
     First,
+    Polyline,
     WaitingForRadius,
     Second {
         h1: Handle,
@@ -1072,7 +1377,12 @@ impl CadCommand for FilletCommand {
     fn prompt(&self) -> String {
         match &self.step {
             FilletStep::First => crate::tf!(
-                "FILLET  Select first object (Line/Arc/LwPolyline)  [R={:.4}]:",
+                "FILLET  Select first object or [Polyline/Radius]  [R={:.4}]:",
+                self.radius
+            )
+            .into_owned(),
+            FilletStep::Polyline => crate::tf!(
+                "FILLET  Select 2D polyline  [R={:.4}]:",
                 self.radius
             )
             .into_owned(),
@@ -1091,11 +1401,16 @@ impl CadCommand for FilletCommand {
 
     fn options(&self) -> Vec<crate::command::CmdOption> {
         use crate::command::CmdOption;
+
         match self.step {
-            // Offer the radius keyword while selecting objects; the "R" token is
-            // already handled by on_text_input.
-            FilletStep::First | FilletStep::Second { .. } => vec![CmdOption::new("Radius", "R")],
-            FilletStep::WaitingForRadius => vec![],
+            FilletStep::First => vec![
+                CmdOption::new("Polyline", "P"),
+                CmdOption::new("Radius", "R"),
+            ],
+            FilletStep::Second { .. } => {
+                vec![CmdOption::new("Radius", "R")]
+            }
+            FilletStep::Polyline | FilletStep::WaitingForRadius => vec![],
         }
     }
 
@@ -1134,6 +1449,10 @@ impl CadCommand for FilletCommand {
             FilletStep::First | FilletStep::Second { .. } => {
                 let t = text.trim();
                 let upper = t.to_uppercase();
+                if matches!(self.step, FilletStep::First) && upper == "P" {
+                    self.step = FilletStep::Polyline;
+                    return Some(CmdResult::NeedPoint);
+                }
                 // "R" alone → enter sub-step to collect radius
                 if upper == "R" {
                     self.enter_radius_substep();
@@ -1156,6 +1475,7 @@ impl CadCommand for FilletCommand {
                 }
                 None
             }
+            FilletStep::Polyline => None,
         }
     }
 
@@ -1171,6 +1491,28 @@ impl CadCommand for FilletCommand {
 
         match &self.step {
             FilletStep::WaitingForRadius => return CmdResult::NeedPoint,
+            FilletStep::Polyline => {
+                let poly = self
+                    .entity_index
+                    .get(&self.all_entities, handle)
+                    .and_then(|entity| match entity {
+                        EntityType::LwPolyline(poly) => Some(poly.clone()),
+                        _ => None,
+                    });
+
+                let Some(poly) = poly else {
+                    return CmdResult::NeedPoint;
+                };
+
+                let Some(result) = fillet_entire_lwpolyline(&poly, self.radius) else {
+                    return CmdResult::NeedPoint;
+                };
+
+                self.continue_after_fillet(vec![(
+                    handle,
+                    vec![EntityType::LwPolyline(result)],
+                )])
+            }
             FilletStep::First => {
                 let e1 = self
                     .entity_index
@@ -1245,6 +1587,28 @@ impl CadCommand for FilletCommand {
 
         match &self.step {
             FilletStep::WaitingForRadius => vec![],
+            FilletStep::Polyline => {
+                let preview = self
+                    .entity_index
+                    .get(&self.all_entities, handle)
+                    .and_then(|entity| match entity {
+                        EntityType::LwPolyline(poly) => {
+                            fillet_entire_lwpolyline(poly, self.radius)
+                        }
+                        _ => None,
+                    });
+
+                preview
+                    .map(|poly| {
+                        vec![WireModel::solid(
+                            "fillet_polyline_preview".into(),
+                            lwpoly_pts(&poly),
+                            WireModel::CYAN,
+                            false,
+                        )]
+                    })
+                    .unwrap_or_default()
+            }
             FilletStep::First => {
                 let pts = self
                     .entity_index
@@ -1515,12 +1879,13 @@ impl CadCommand for ChamferCommand {
 
     fn options(&self) -> Vec<crate::command::CmdOption> {
         use crate::command::CmdOption;
+
         match self.step {
-            // Offer the distance keyword while selecting objects; the "D" token
-            // is already handled by on_text_input.
             ChamferStep::First
             | ChamferStep::Second { .. }
-            | ChamferStep::SecondPoly { .. } => vec![CmdOption::new(t!("Distance").as_ref(), "D")],
+            | ChamferStep::SecondPoly { .. } => {
+                vec![CmdOption::new(t!("Distance").as_ref(), "D")]
+            }
             ChamferStep::WaitingForDist1 | ChamferStep::WaitingForDist2 => vec![],
         }
     }

src/modules/draw/select.rs

@@ -17,6 +17,7 @@ use crate::modules::draw::fence::FencePick;
 use crate::scene::model::wire_model::WireModel;
 
 pub struct SelectObjectsCommand {
+    prompt_cmd: String,
     pending_cmd: String,
     /// Selection accumulated so far (kept in sync with the scene selection by
     /// each `on_selection_complete` call). Applied on Enter when `commit_on_enter`.
@@ -24,6 +25,8 @@ pub struct SelectObjectsCommand {
     /// When true, gathering continues until Enter / right-click commits the set.
     /// When false, the first completed selection action fires immediately.
     commit_on_enter: bool,
+    /// Whether the generic selection methods are shown as command buttons.
+    show_options: bool,
     /// A Fence / WPolygon / CPolygon path being picked point by point. While
     /// one is under way the host must send clicks here as points rather than
     /// treating them as picks, which is what `is_selection_gathering` reports.
@@ -37,9 +40,25 @@ impl SelectObjectsCommand {
     /// Standard selection set: accumulate picks, apply on Enter / right-click.
     pub fn new(pending_cmd: &str) -> Self {
         Self {
+            prompt_cmd: pending_cmd.to_string(),
             pending_cmd: pending_cmd.to_string(),
             handles: Vec::new(),
             commit_on_enter: true,
+            show_options: true,
+            pick: None,
+            pick_crossing: true,
+        }
+    }
+
+    /// Plain gather prompt with no generic selection-method buttons. The
+    /// visible command name may differ from the private apply command.
+    pub fn plain(prompt_cmd: &str, pending_cmd: &str) -> Self {
+        Self {
+            prompt_cmd: prompt_cmd.to_string(),
+            pending_cmd: pending_cmd.to_string(),
+            handles: Vec::new(),
+            commit_on_enter: true,
+            show_options: false,
             pick: None,
             pick_crossing: true,
         }
@@ -49,9 +68,11 @@ impl SelectObjectsCommand {
     /// immediately, with no Enter (used by commands that act on one object).
     pub fn instant(pending_cmd: &str) -> Self {
         Self {
+            prompt_cmd: pending_cmd.to_string(),
             pending_cmd: pending_cmd.to_string(),
             handles: Vec::new(),
             commit_on_enter: false,
+            show_options: false,
             pick: None,
             pick_crossing: true,
         }
@@ -82,12 +103,12 @@ impl CadCommand for SelectObjectsCommand {
         if self.commit_on_enter && !self.handles.is_empty() {
             t!(
                 "%{cmd}  Select objects (%{count} selected, Enter to apply):",
-                cmd = self.pending_cmd,
+                cmd = self.prompt_cmd,
                 count = self.handles.len()
             )
             .into_owned()
         } else {
-            t!("%{cmd}  Select objects:", cmd = self.pending_cmd).into_owned()
+            t!("%{cmd}  Select objects:", cmd = self.prompt_cmd).into_owned()
         }
     }
 
@@ -108,7 +129,7 @@ impl CadCommand for SelectObjectsCommand {
     // they work typed as well — these buttons only surface them, which is what
     // the on-screen keyboard-less case needs.
     fn options(&self) -> Vec<CmdOption> {
-        if self.commit_on_enter {
+        if self.commit_on_enter && self.show_options {
             vec![
                 CmdOption::new(t!("Window").as_ref(), "W"),
                 CmdOption::new(t!("Crossing").as_ref(), "C"),

src/modules/insert/solid3d_cmds.rs

@@ -2211,7 +2211,7 @@ impl LoftCommand {
     fn option_prompt(&self) -> String {
         match self.state.step {
             LoftStep::Sections => format!(
-                "{} ({}):", t!("LOFT  Select cross-sections in order or [Point/Join/Mode/Undo] (Enter to finish)"),
+                "{} ({}):", t!("LOFT  Select cross-sections in order or [Point/Join/Mode] (Enter to finish)"),
                 self.state.sections.len(),
             ),
             LoftStep::Join => format!(
@@ -2224,9 +2224,9 @@ impl LoftCommand {
             LoftStep::Options => {
                 let (start, end) = self.point_ends();
                 if start || end {
-                    t!("LOFT  Enter an option [Guides/Path/Cross sections only/Settings/Continuity/Bulge magnitude/Mode/Undo] <Cross sections only>:").into_owned()
+                    t!("LOFT  Enter an option [Guides/Path/Cross sections only/Settings/Continuity/Bulge magnitude] <Cross sections only>:").into_owned()
                 } else {
-                    t!("LOFT  Enter an option [Guides/Path/Cross sections only/Settings/Mode/Undo] <Cross sections only>:").into_owned()
+                    t!("LOFT  Enter an option [Guides/Path/Cross sections only/Settings] <Cross sections only>:").into_owned()
                 }
             }
             LoftStep::Guides => format!("{} ({}):", t!("LOFT  Select guide curves or [Undo] (Enter to finish)"), self.state.guides.len()),
@@ -2272,7 +2272,7 @@ impl CadCommand for LoftCommand {
     }
     fn options(&self) -> Vec<CmdOption> {
         let mut options = match self.state.step {
-            LoftStep::Sections => vec![CmdOption::new("Point", "POINT"), CmdOption::new("Join", "JOIN"), CmdOption::new("Mode", "MODE"), CmdOption::enter("Done")],
+            LoftStep::Sections => vec![CmdOption::new("Point", "POINT"), CmdOption::new("Join", "JOIN"), CmdOption::new("Mode", "MODE")],
             LoftStep::Join | LoftStep::Guides => vec![CmdOption::enter("Done")],
             LoftStep::Mode => vec![CmdOption::new("Solid", "SOLID"), CmdOption::new("Surface", "SURFACE")],
             LoftStep::Options => {
@@ -2282,7 +2282,6 @@ impl CadCommand for LoftCommand {
                     choices.push(CmdOption::new("Continuity", "CONTINUITY"));
                     choices.push(CmdOption::new("Bulge magnitude", "BULGE"));
                 }
-                choices.push(CmdOption::new("Mode", "MODE"));
                 choices
             }
             LoftStep::Settings => {
@@ -2308,7 +2307,9 @@ impl CadCommand for LoftCommand {
             LoftStep::StartContinuity | LoftStep::EndContinuity => vec![CmdOption::new("G0", "G0"), CmdOption::new("G1", "G1")],
             _ => Vec::new(),
         };
-        options.push(CmdOption::new("Undo", "UNDO"));
+        if !matches!(self.state.step, LoftStep::Sections | LoftStep::Options) {
+            options.push(CmdOption::new("Undo", "UNDO"));
+        }
         options
     }
     fn needs_entity_pick(&self) -> bool {

src/modules/model/boolean_cmd.rs

@@ -25,16 +25,20 @@ impl BoolOp {
 enum SubtractStep {
     Bases,
     Cutters,
+    ConvertMeshes,
 }
 
 pub struct SubtractCommand {
     step: SubtractStep,
     bases: Vec<Handle>,
+    cutters: Vec<Handle>,
     selected: Vec<Handle>,
+    bases_have_mesh: bool,
+    selected_has_mesh: bool,
 }
 
 impl SubtractCommand {
-    pub fn new(bases: Vec<Handle>) -> Self {
+    pub fn new(bases: Vec<Handle>, bases_have_mesh: bool) -> Self {
         let step = if bases.is_empty() {
             SubtractStep::Bases
         } else {
@@ -43,7 +47,18 @@ impl SubtractCommand {
         Self {
             step,
             bases,
+            cutters: Vec::new(),
             selected: Vec::new(),
+            bases_have_mesh,
+            selected_has_mesh: false,
+        }
+    }
+
+    fn finish(&mut self, convert_meshes: bool) -> CmdResult {
+        CmdResult::SolidSubtract {
+            bases: std::mem::take(&mut self.bases),
+            cutters: std::mem::take(&mut self.cutters),
+            convert_meshes,
         }
     }
 }
@@ -55,11 +70,26 @@ impl CadCommand for SubtractCommand {
 
     fn prompt(&self) -> String {
         match self.step {
-            SubtractStep::Bases => crate::t!("SUBTRACT  Select base solids, then press Enter:")
+            SubtractStep::Bases => crate::t!("SUBTRACT  Select base Solids, Regions, Surfaces, or Meshes, then press Enter:")
                 .into_owned(),
             SubtractStep::Cutters => {
-                crate::t!("SUBTRACT  Select solids to subtract, then press Enter:").into_owned()
+                crate::t!("SUBTRACT  Select Solids, Regions, Surfaces, or Meshes to subtract, then press Enter:").into_owned()
             }
+            SubtractStep::ConvertMeshes => crate::t!(
+                "SUBTRACT  Convert selected closed Mesh objects to solids? [Yes/No] <Yes>:"
+            )
+            .into_owned(),
+        }
+    }
+
+    fn options(&self) -> Vec<crate::command::CmdOption> {
+        if matches!(self.step, SubtractStep::ConvertMeshes) {
+            vec![
+                crate::command::CmdOption::new(crate::t!("Yes").as_ref(), "Y"),
+                crate::command::CmdOption::new(crate::t!("No").as_ref(), "N"),
+            ]
+        } else {
+            Vec::new()
         }
     }
 
@@ -68,31 +98,72 @@ impl CadCommand for SubtractCommand {
     }
 
     fn on_enter(&mut self) -> CmdResult {
+        if matches!(self.step, SubtractStep::ConvertMeshes) {
+            return self.finish(true);
+        }
         if self.selected.is_empty() {
             return CmdResult::NeedPoint;
         }
         match self.step {
             SubtractStep::Bases => {
                 self.bases = std::mem::take(&mut self.selected);
+                self.bases_have_mesh = self.selected_has_mesh;
+                self.selected_has_mesh = false;
                 self.step = SubtractStep::Cutters;
                 CmdResult::DeselectAndContinue
             }
-            SubtractStep::Cutters => CmdResult::SolidSubtract {
-                bases: std::mem::take(&mut self.bases),
-                cutters: std::mem::take(&mut self.selected),
-            },
+            SubtractStep::Cutters => {
+                self.cutters = std::mem::take(&mut self.selected);
+                if self.bases_have_mesh || self.selected_has_mesh {
+                    self.step = SubtractStep::ConvertMeshes;
+                    CmdResult::NeedPoint
+                } else {
+                    self.finish(false)
+                }
+            }
+            SubtractStep::ConvertMeshes => unreachable!(),
         }
     }
 
+    fn wants_text_input(&self) -> bool {
+        matches!(self.step, SubtractStep::ConvertMeshes)
+    }
+
+    fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
+        if !matches!(self.step, SubtractStep::ConvertMeshes) {
+            return None;
+        }
+        Some(match text.trim().to_ascii_lowercase().as_str() {
+            "" | "y" | "yes" => self.finish(true),
+            "n" | "no" => self.finish(false),
+            _ => CmdResult::NeedPoint,
+        })
+    }
+
     fn is_selection_gathering(&self) -> bool {
-        true
+        !matches!(self.step, SubtractStep::ConvertMeshes)
     }
 
     fn inject_selection_entities(&mut self, entities: Vec<SelectionEntity>) {
+        self.selected_has_mesh = entities.iter().any(|entity| {
+            matches!(
+                entity.entity,
+                EntityType::Mesh(_) | EntityType::PolygonMesh(_) | EntityType::PolyfaceMesh(_)
+            )
+        });
         self.selected = entities
             .into_iter()
             .filter_map(|entity| {
-                matches!(entity.entity, EntityType::Solid3D(_)).then_some(entity.handle)
+                matches!(
+                    entity.entity,
+                    EntityType::Solid3D(_)
+                        | EntityType::Region(_)
+                        | EntityType::Surface(_)
+                        | EntityType::Mesh(_)
+                        | EntityType::PolygonMesh(_)
+                        | EntityType::PolyfaceMesh(_)
+                )
+                .then_some(entity.handle)
             })
             .collect();
     }

src/modules/model/edge_cmd.rs

@@ -1,42 +1,311 @@
+use std::sync::atomic::{AtomicU64, Ordering};
+
 use acadrust::Handle;
+use cadkernel::brep::{Body, EdgeKey, FaceKey};
 use glam::DVec3;
 
 use crate::command::{
-    CadCommand, CmdResult, DynAnchor, DynFieldSpec, DynGuide, DynRole, DynSpec,
+    CadCommand, CmdOption, CmdResult, DynAnchor, DynFieldSpec, DynGuide, DynRole, DynSpec,
 };
+use crate::scene::model::wire_model::WireModel;
 
-#[derive(Clone, Copy)]
+static FILLET_RADIUS_BITS: AtomicU64 = AtomicU64::new(1.0f64.to_bits());
+
+fn fillet_radius() -> f64 {
+    f64::from_bits(FILLET_RADIUS_BITS.load(Ordering::Relaxed))
+}
+
+fn set_fillet_radius(value: f64) {
+    FILLET_RADIUS_BITS.store(value.to_bits(), Ordering::Relaxed);
+}
+
+#[derive(Clone, Copy, PartialEq, Eq)]
 pub enum EdgeOperation {
     Fillet,
     Chamfer,
 }
 
+#[derive(Clone, Copy, PartialEq, Eq)]
+enum EdgeSelectionMode {
+    Edge,
+    Chain,
+}
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+enum EdgeStep {
+    Selecting,
+    PickingLoop,
+    LoopConfirm,
+    PreviewConfirm,
+    Radius,
+    Expression,
+    ChamferDistance1,
+    ChamferDistance2,
+}
+
 pub struct SolidEdgeCommand {
     operation: EdgeOperation,
     target: Option<Handle>,
-    picked: Option<(Handle, DVec3)>,
+    bodies: Vec<(Handle, Body)>,
+    handle: Option<Handle>,
+    selected_edges: Vec<EdgeKey>,
+    base_face: Option<FaceKey>,
+    selection_batches: Vec<(Vec<EdgeKey>, DVec3)>,
+    selection_mode: EdgeSelectionMode,
+    step: EdgeStep,
+    value_return: EdgeStep,
+    expression_return: EdgeStep,
+    loop_candidates: Vec<(FaceKey, Vec<EdgeKey>)>,
+    loop_index: usize,
+    last_pick: Option<DVec3>,
     default_value: f64,
+    other_value: f64,
+    preview_color: [f32; 4],
+    preview_wires: Vec<WireModel>,
+    preview_hidden: Vec<Handle>,
 }
 
 impl SolidEdgeCommand {
-    pub fn new(operation: EdgeOperation, target: Option<Handle>) -> Self {
+    pub fn new(
+        operation: EdgeOperation,
+        target: Option<Handle>,
+        bodies: Vec<(Handle, Body)>,
+        preview_color: [f32; 4],
+    ) -> Self {
         Self {
             operation,
             target,
-            picked: None,
-            default_value: 1.0,
+            bodies,
+            handle: None,
+            selected_edges: Vec::new(),
+            base_face: None,
+            selection_batches: Vec::new(),
+            selection_mode: EdgeSelectionMode::Edge,
+            step: EdgeStep::Selecting,
+            value_return: EdgeStep::Selecting,
+            expression_return: EdgeStep::Radius,
+            loop_candidates: Vec::new(),
+            loop_index: 0,
+            last_pick: None,
+            default_value: if operation == EdgeOperation::Fillet {
+                fillet_radius()
+            } else {
+                1.0
+            },
+            other_value: 1.0,
+            preview_color,
+            preview_wires: Vec::new(),
+            preview_hidden: Vec::new(),
         }
     }
 
-    fn finish(&self, value: f64) -> CmdResult {
-        let Some((handle, pick)) = self.picked else {
+    pub fn new_chamfer(
+        target: Option<Handle>,
+        bodies: Vec<(Handle, Body)>,
+        preview_color: [f32; 4],
+        distances: (f64, f64),
+    ) -> Self {
+        let mut command = Self::new(EdgeOperation::Chamfer, target, bodies, preview_color);
+        command.default_value = positive_default(distances.0);
+        command.other_value = positive_default(distances.1);
+        command
+    }
+
+    pub fn chamfer_distances(&self) -> (f64, f64) {
+        (self.default_value, self.other_value)
+    }
+
+    fn body(&self, handle: Handle) -> Option<&Body> {
+        self.bodies
+            .iter()
+            .find_map(|(candidate, body)| (*candidate == handle).then_some(body))
+    }
+
+    fn active_body(&self) -> Option<(Handle, &Body)> {
+        let handle = self.handle?;
+        self.body(handle).map(|body| (handle, body))
+    }
+
+    fn pick_allowed(&self, handle: Handle) -> bool {
+        !handle.is_null()
+            && self.target.is_none_or(|target| target == handle)
+            && self.handle.is_none_or(|selected| selected == handle)
+            && self.body(handle).is_some()
+    }
+
+    fn add_batch(&mut self, edges: Vec<EdgeKey>, anchor: DVec3) -> bool {
+        let batch = edges
+            .into_iter()
+            .filter(|edge| !self.selected_edges.contains(edge))
+            .collect::<Vec<_>>();
+        if batch.is_empty() {
+            return false;
+        }
+        self.selected_edges.extend(batch.iter().copied());
+        self.selection_batches.push((batch, anchor));
+        true
+    }
+
+    fn current_loop(&self) -> Option<&[EdgeKey]> {
+        self.loop_candidates
+            .get(self.loop_index)
+            .map(|(_, edges)| edges.as_slice())
+    }
+
+    fn current_loop_face(&self) -> Option<FaceKey> {
+        self.loop_candidates
+            .get(self.loop_index)
+            .map(|(face, _)| *face)
+    }
+
+    fn preview_edges(&self) -> Vec<EdgeKey> {
+        let mut edges = self.selected_edges.clone();
+        if self.step == EdgeStep::LoopConfirm {
+            if let Some(loop_edges) = self.current_loop() {
+                for edge in loop_edges {
+                    if !edges.contains(edge) {
+                        edges.push(*edge);
+                    }
+                }
+            }
+        }
+        edges
+    }
+
+    fn preview_active(&self) -> bool {
+        matches!(
+            self.step,
+            EdgeStep::Selecting
+                | EdgeStep::PickingLoop
+                | EdgeStep::LoopConfirm
+                | EdgeStep::PreviewConfirm
+                | EdgeStep::Radius
+                | EdgeStep::Expression
+                | EdgeStep::ChamferDistance1
+                | EdgeStep::ChamferDistance2
+        )
+    }
+
+    fn preview_for_values(
+        &self,
+        value: f64,
+        other_value: f64,
+    ) -> Option<(Handle, Vec<WireModel>)> {
+        if !self.preview_active() {
+            return None;
+        }
+        let edges = self.preview_edges();
+        if edges.is_empty() {
+            return None;
+        }
+        let (handle, body) = self.active_body()?;
+        let result = match self.operation {
+            EdgeOperation::Fillet => cadkernel::brep::fillet_edges(body, &edges, value).ok()?,
+            EdgeOperation::Chamfer => cadkernel::brep::chamfer_edges(
+                body,
+                &edges,
+                self.base_face.or_else(|| self.current_loop_face())?,
+                value,
+                other_value,
+            )
+            .ok()?,
+        };
+        let mut wires = crate::scene::model::solid_model::grip_preview_wires(&result, handle);
+        for wire in &mut wires {
+            wire.color = self.preview_color;
+            wire.name = format!("{}-{}-PREVIEW", handle.value(), self.name());
+        }
+        (!wires.is_empty()).then_some((handle, wires))
+    }
+
+    fn rebuild_preview(&mut self) {
+        self.preview_wires.clear();
+        self.preview_hidden.clear();
+        if let Some((handle, wires)) =
+            self.preview_for_values(self.default_value, self.other_value)
+        {
+            self.preview_wires = wires;
+            self.preview_hidden.push(handle);
+        }
+    }
+
+    fn begin_radius(&mut self, return_to: EdgeStep) -> CmdResult {
+        self.value_return = return_to;
+        self.step = EdgeStep::Radius;
+        self.rebuild_preview();
+        CmdResult::NeedPoint
+    }
+
+    fn accept_radius(&mut self, value: f64) -> Option<CmdResult> {
+        if value <= 0.0 || !value.is_finite() {
+            return None;
+        }
+        self.default_value = value;
+        if self.operation == EdgeOperation::Fillet {
+            set_fillet_radius(value);
+        }
+        self.step = self.value_return;
+        self.rebuild_preview();
+        Some(CmdResult::NeedPoint)
+    }
+
+    fn begin_distances(&mut self, return_to: EdgeStep) -> CmdResult {
+        self.value_return = return_to;
+        self.step = EdgeStep::ChamferDistance1;
+        self.rebuild_preview();
+        CmdResult::NeedPoint
+    }
+
+    fn accept_distance(&mut self, value: f64) -> Option<CmdResult> {
+        if value <= 0.0 || !value.is_finite() {
+            return None;
+        }
+        match self.step {
+            EdgeStep::ChamferDistance1 => {
+                self.default_value = value;
+                self.step = EdgeStep::ChamferDistance2;
+            }
+            EdgeStep::ChamferDistance2 => {
+                self.other_value = value;
+                self.step = self.value_return;
+            }
+            _ => return None,
+        }
+        self.rebuild_preview();
+        Some(CmdResult::NeedPoint)
+    }
+
+    fn accept_loop(&mut self) -> CmdResult {
+        if let (Some(edges), Some(anchor)) = (
+            self.current_loop().map(|edges| edges.to_vec()),
+            self.last_pick,
+        ) {
+            if self.operation == EdgeOperation::Chamfer && self.base_face.is_none() {
+                self.base_face = self.current_loop_face();
+            }
+            self.add_batch(edges, anchor);
+        }
+        self.loop_candidates.clear();
+        self.loop_index = 0;
+        self.step = EdgeStep::Selecting;
+        self.rebuild_preview();
+        CmdResult::NeedPoint
+    }
+
+    fn finish(&self) -> CmdResult {
+        let Some(handle) = self.handle else {
             return CmdResult::Cancel;
         };
+        if self.selected_edges.is_empty() {
+            return CmdResult::Cancel;
+        }
         CmdResult::SolidEdgeBlend {
             handle,
-            pick,
-            value,
-            fillet: matches!(self.operation, EdgeOperation::Fillet),
+            edges: self.selected_edges.clone(),
+            base_face: self.base_face,
+            value: self.default_value,
+            other_value: self.other_value,
+            fillet: self.operation == EdgeOperation::Fillet,
         }
     }
 }
@@ -44,27 +313,114 @@ impl SolidEdgeCommand {
 impl CadCommand for SolidEdgeCommand {
     fn name(&self) -> &'static str {
         match self.operation {
-            EdgeOperation::Fillet => "SOLIDFILLET",
-            EdgeOperation::Chamfer => "SOLIDCHAMFER",
+            EdgeOperation::Fillet => "FILLETEDGE",
+            EdgeOperation::Chamfer => "CHAMFEREDGE",
         }
     }
 
     fn prompt(&self) -> String {
-        if self.picked.is_none() {
-            return crate::t!("Select a solid edge:").into_owned();
+        match (self.operation, self.step, self.selection_mode) {
+            (EdgeOperation::Chamfer, EdgeStep::Selecting, _) => {
+                crate::t!("Select an edge or [Loop/Distance]:").into_owned()
+            }
+            (EdgeOperation::Chamfer, EdgeStep::PickingLoop, _) => {
+                crate::t!("Select edge of loop or [Edge/Distance]:").into_owned()
+            }
+            (EdgeOperation::Chamfer, EdgeStep::PreviewConfirm, _) => {
+                crate::t!("Press Enter to accept the chamfer or [Distance]:").into_owned()
+            }
+            (EdgeOperation::Chamfer, EdgeStep::ChamferDistance1, _) => crate::tf!(
+                "Specify Distance1 or [Expression] <{:.4}>:",
+                self.default_value
+            )
+            .into_owned(),
+            (EdgeOperation::Chamfer, EdgeStep::ChamferDistance2, _) => crate::tf!(
+                "Specify Distance2 or [Expression] <{:.4}>:",
+                self.other_value
+            )
+            .into_owned(),
+            (_, EdgeStep::Selecting, EdgeSelectionMode::Edge) => {
+                crate::t!("Select an edge or [Chain/Loop/Radius]:").into_owned()
+            }
+            (_, EdgeStep::Selecting, EdgeSelectionMode::Chain) => {
+                crate::t!("Select an edge chain or [Edge/Radius]:").into_owned()
+            }
+            (_, EdgeStep::PickingLoop, _) => {
+                crate::t!("Select edge of loop or [Edge/Chain/Radius]:").into_owned()
+            }
+            (_, EdgeStep::LoopConfirm, _) => {
+                crate::t!("Enter an option [Accept/Next] <Accept>:").into_owned()
+            }
+            (_, EdgeStep::PreviewConfirm, _) => {
+                crate::t!("Press Enter to accept the fillet or [Radius]:").into_owned()
+            }
+            (_, EdgeStep::Radius, _) if self.value_return == EdgeStep::PreviewConfirm => crate::tf!(
+                "Specify Radius or [Expression] <{:.4}>:",
+                self.default_value
+            )
+            .into_owned(),
+            (_, EdgeStep::Radius, _) => crate::tf!(
+                "Enter fillet radius or [Expression] <{:.4}>:",
+                self.default_value
+            )
+            .into_owned(),
+            (_, EdgeStep::Expression, _) => crate::t!("Enter expression:").into_owned(),
+            _ => String::new(),
         }
-        match self.operation {
-            EdgeOperation::Fillet => {
-                crate::tf!("Specify fillet radius <{:.3}>:", self.default_value).into_owned()
+    }
+
+    fn options(&self) -> Vec<CmdOption> {
+        match (self.operation, self.step, self.selection_mode) {
+            (EdgeOperation::Chamfer, EdgeStep::Selecting, _) => vec![
+                CmdOption::new("Loop", "L"),
+                CmdOption::new("Distance", "D"),
+            ],
+            (EdgeOperation::Chamfer, EdgeStep::PickingLoop, _) => vec![
+                CmdOption::new("Edge", "E"),
+                CmdOption::new("Distance", "D"),
+            ],
+            (EdgeOperation::Chamfer, EdgeStep::LoopConfirm, _) => vec![
+                CmdOption::new("Accept", "A"),
+                CmdOption::new("Next", "N"),
+            ],
+            (EdgeOperation::Chamfer, EdgeStep::PreviewConfirm, _) => {
+                vec![CmdOption::new("Distance", "D")]
             }
-            EdgeOperation::Chamfer => {
-                crate::tf!("Specify chamfer distance <{:.3}>:", self.default_value).into_owned()
+            (
+                EdgeOperation::Chamfer,
+                EdgeStep::ChamferDistance1 | EdgeStep::ChamferDistance2,
+                _,
+            ) => vec![CmdOption::new("Expression", "E")],
+            (EdgeOperation::Fillet, EdgeStep::Selecting, EdgeSelectionMode::Edge) => vec![
+                CmdOption::new("Chain", "C"),
+                CmdOption::new("Loop", "L"),
+                CmdOption::new("Radius", "R"),
+            ],
+            (EdgeOperation::Fillet, EdgeStep::Selecting, EdgeSelectionMode::Chain) => vec![
+                CmdOption::new("Edge", "E"),
+                CmdOption::new("Radius", "R"),
+            ],
+            (EdgeOperation::Fillet, EdgeStep::PickingLoop, _) => vec![
+                CmdOption::new("Edge", "E"),
+                CmdOption::new("Chain", "C"),
+                CmdOption::new("Radius", "R"),
+            ],
+            (EdgeOperation::Fillet, EdgeStep::LoopConfirm, _) => vec![
+                CmdOption::new("Accept", "A"),
+                CmdOption::new("Next", "N"),
+            ],
+            (EdgeOperation::Fillet, EdgeStep::PreviewConfirm, _) => {
+                vec![CmdOption::new("Radius", "R")]
             }
+            (EdgeOperation::Fillet, EdgeStep::Radius, _) => {
+                vec![CmdOption::new("Expression", "E")]
+            }
+            _ => Vec::new(),
         }
     }
 
     fn needs_entity_pick(&self) -> bool {
-        self.picked.is_none()
+        matches!(self.step, EdgeStep::Selecting | EdgeStep::PickingLoop)
     }
 
     fn entity_pick_includes_fills(&self) -> bool {
@@ -80,52 +436,281 @@ impl CadCommand for SolidEdgeCommand {
     }
 
     fn on_entity_pick(&mut self, handle: Handle, point: DVec3) -> CmdResult {
-        if handle.is_null() || self.target.is_some_and(|target| target != handle) {
+        if !self.pick_allowed(handle) {
             return CmdResult::NeedPoint;
         }
-        self.picked = Some((handle, point));
+        let Some(seed) = self
+            .body(handle)
+            .and_then(|body| crate::scene::model::solid_model::nearest_edge(body, point.to_array()))
+        else {
+            return CmdResult::NeedPoint;
+        };
+        self.handle = Some(handle);
+        self.last_pick = Some(point);
+
+        if self.step == EdgeStep::PickingLoop {
+            self.loop_candidates = edge_loops(self.body(handle).expect("pick body exists"), seed);
+            if self.operation == EdgeOperation::Chamfer {
+                if let Some(base_face) = self.base_face {
+                    self.loop_candidates
+                        .retain(|(face, _)| *face == base_face);
+                }
+            }
+            self.loop_index = 0;
+            self.step = if self.loop_candidates.is_empty() {
+                EdgeStep::Selecting
+            } else {
+                EdgeStep::LoopConfirm
+            };
+            self.rebuild_preview();
+            return CmdResult::NeedPoint;
+        }
+
+        if self.operation == EdgeOperation::Chamfer {
+            if self.base_face.is_none() {
+                self.base_face = self.body(handle).and_then(|body| {
+                    nearest_edge_face(body, seed, point.to_array())
+                });
+            }
+            let Some(base_face) = self.base_face else {
+                return CmdResult::NeedPoint;
+            };
+            if !edge_belongs_to_face(self.body(handle).expect("pick body exists"), seed, base_face)
+            {
+                return CmdResult::NeedPoint;
+            }
+            self.add_batch(vec![seed], point);
+            self.rebuild_preview();
+            return CmdResult::NeedPoint;
+        }
+
+        let edges = match self.selection_mode {
+            EdgeSelectionMode::Edge => vec![seed],
+            EdgeSelectionMode::Chain => edge_chain(self.body(handle).expect("pick body exists"), seed),
+        };
+        self.add_batch(edges, point);
+        self.rebuild_preview();
         CmdResult::NeedPoint
     }
 
     fn on_point(&mut self, point: DVec3) -> CmdResult {
-        let Some((_, pick)) = self.picked else {
+        if !matches!(
+            self.step,
+            EdgeStep::Radius | EdgeStep::ChamferDistance1 | EdgeStep::ChamferDistance2
+        ) {
+            return CmdResult::NeedPoint;
+        }
+        let Some(anchor) = self.last_pick else {
             return CmdResult::NeedPoint;
         };
-        let value = point.distance(pick);
-        if value > 0.0 && value.is_finite() {
-            self.finish(value)
-        } else {
-            CmdResult::NeedPoint
+        let value = point.distance(anchor);
+        if value <= 0.0 || !value.is_finite() {
+            return CmdResult::NeedPoint;
+        }
+        match self.step {
+            EdgeStep::Radius => self.accept_radius(value).unwrap_or(CmdResult::NeedPoint),
+            EdgeStep::ChamferDistance1 | EdgeStep::ChamferDistance2 => {
+                self.accept_distance(value).unwrap_or(CmdResult::NeedPoint)
+            }
+            _ => CmdResult::NeedPoint,
         }
     }
 
     fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
-        if self.picked.is_none() {
-            return None;
+        let keyword = text.trim().to_ascii_uppercase();
+        if self.operation == EdgeOperation::Chamfer {
+            return match self.step {
+                EdgeStep::Selecting => match keyword.as_str() {
+                    "L" | "LOOP" => {
+                        self.step = EdgeStep::PickingLoop;
+                        Some(CmdResult::NeedPoint)
+                    }
+                    "D" | "DISTANCE" => Some(self.begin_distances(EdgeStep::Selecting)),
+                    _ => None,
+                },
+                EdgeStep::PickingLoop => match keyword.as_str() {
+                    "E" | "EDGE" => {
+                        self.step = EdgeStep::Selecting;
+                        Some(CmdResult::NeedPoint)
+                    }
+                    "D" | "DISTANCE" => Some(self.begin_distances(EdgeStep::PickingLoop)),
+                    _ => None,
+                },
+                EdgeStep::LoopConfirm => match keyword.as_str() {
+                    "A" | "ACCEPT" => Some(self.accept_loop()),
+                    "N" | "NEXT" if !self.loop_candidates.is_empty() => {
+                        self.loop_index = (self.loop_index + 1) % self.loop_candidates.len();
+                        self.rebuild_preview();
+                        Some(CmdResult::NeedPoint)
+                    }
+                    _ => None,
+                },
+                EdgeStep::PreviewConfirm => match keyword.as_str() {
+                    "D" | "DISTANCE" => Some(self.begin_distances(EdgeStep::PreviewConfirm)),
+                    _ => None,
+                },
+                EdgeStep::ChamferDistance1 | EdgeStep::ChamferDistance2 => {
+                    if matches!(keyword.as_str(), "E" | "EXPRESSION") {
+                        self.expression_return = self.step;
+                        self.step = EdgeStep::Expression;
+                        Some(CmdResult::NeedPoint)
+                    } else {
+                        let value = keyword.parse::<f64>().ok()?;
+                        self.accept_distance(value)
+                    }
+                }
+                EdgeStep::Expression => {
+                    let value = crate::app::expr_eval::eval_number(text)?;
+                    self.step = self.expression_return;
+                    self.accept_distance(value)
+                }
+                EdgeStep::Radius => None,
+            };
+        }
+
+        match self.step {
+            EdgeStep::Selecting => match keyword.as_str() {
+                "R" | "RADIUS" => Some(self.begin_radius(EdgeStep::Selecting)),
+                "C" | "CHAIN" => {
+                    self.selection_mode = EdgeSelectionMode::Chain;
+                    Some(CmdResult::NeedPoint)
+                }
+                "E" | "EDGE" if self.selection_mode == EdgeSelectionMode::Chain => {
+                    self.selection_mode = EdgeSelectionMode::Edge;
+                    Some(CmdResult::NeedPoint)
+                }
+                "L" | "LOOP" => {
+                    self.step = EdgeStep::PickingLoop;
+                    Some(CmdResult::NeedPoint)
+                }
+                _ => None,
+            },
+            EdgeStep::PickingLoop => match keyword.as_str() {
+                "E" | "EDGE" => {
+                    self.selection_mode = EdgeSelectionMode::Edge;
+                    self.step = EdgeStep::Selecting;
+                    Some(CmdResult::NeedPoint)
+                }
+                "C" | "CHAIN" => {
+                    self.selection_mode = EdgeSelectionMode::Chain;
+                    self.step = EdgeStep::Selecting;
+                    Some(CmdResult::NeedPoint)
+                }
+                "R" | "RADIUS" => Some(self.begin_radius(EdgeStep::PickingLoop)),
+                _ => None,
+            },
+            EdgeStep::LoopConfirm => match keyword.as_str() {
+                "A" | "ACCEPT" => Some(self.accept_loop()),
+                "N" | "NEXT" if !self.loop_candidates.is_empty() => {
+                    self.loop_index = (self.loop_index + 1) % self.loop_candidates.len();
+                    self.rebuild_preview();
+                    Some(CmdResult::NeedPoint)
+                }
+                _ => None,
+            },
+            EdgeStep::PreviewConfirm => match keyword.as_str() {
+                "R" | "RADIUS" => Some(self.begin_radius(EdgeStep::PreviewConfirm)),
+                _ => None,
+            },
+            EdgeStep::Radius => {
+                if matches!(keyword.as_str(), "E" | "EXPRESSION") {
+                    self.step = EdgeStep::Expression;
+                    return Some(CmdResult::NeedPoint);
+                }
+                let value = keyword.parse::<f64>().ok()?;
+                self.accept_radius(value)
+            }
+            EdgeStep::Expression => {
+                let value = crate::app::expr_eval::eval_number(text)?;
+                self.accept_radius(value)
+            }
+            EdgeStep::ChamferDistance1 | EdgeStep::ChamferDistance2 => None,
         }
-        let value = text.trim().parse::<f64>().ok()?;
-        (value > 0.0 && value.is_finite()).then(|| self.finish(value))
     }
 
     fn on_enter(&mut self) -> CmdResult {
-        if self.picked.is_some() {
-            self.finish(self.default_value)
-        } else {
-            CmdResult::Cancel
+        match (self.operation, self.step) {
+            (EdgeOperation::Chamfer, EdgeStep::Selecting) if !self.selected_edges.is_empty() => {
+                self.step = EdgeStep::PreviewConfirm;
+                self.rebuild_preview();
+                CmdResult::NeedPoint
+            }
+            (EdgeOperation::Chamfer, EdgeStep::LoopConfirm) => self.accept_loop(),
+            (EdgeOperation::Chamfer, EdgeStep::PreviewConfirm) => self.finish(),
+            (EdgeOperation::Chamfer, EdgeStep::ChamferDistance1) => self
+                .accept_distance(self.default_value)
+                .unwrap_or(CmdResult::NeedPoint),
+            (EdgeOperation::Chamfer, EdgeStep::ChamferDistance2) => self
+                .accept_distance(self.other_value)
+                .unwrap_or(CmdResult::NeedPoint),
+            (EdgeOperation::Chamfer, EdgeStep::Expression) => CmdResult::NeedPoint,
+            (EdgeOperation::Chamfer, _) => CmdResult::Cancel,
+            (_, EdgeStep::Selecting) if !self.selected_edges.is_empty() => {
+                self.step = EdgeStep::PreviewConfirm;
+                self.rebuild_preview();
+                CmdResult::NeedPoint
+            }
+            (_, EdgeStep::LoopConfirm) => self.accept_loop(),
+            (_, EdgeStep::PreviewConfirm) => self.finish(),
+            (_, EdgeStep::Radius) => self
+                .accept_radius(self.default_value)
+                .unwrap_or(CmdResult::NeedPoint),
+            (_, EdgeStep::Expression) => CmdResult::NeedPoint,
+            _ => CmdResult::Cancel,
         }
     }
 
+    fn on_undo_step(&mut self) -> Option<CmdResult> {
+        if self.step == EdgeStep::LoopConfirm {
+            self.loop_candidates.clear();
+            self.loop_index = 0;
+            self.step = EdgeStep::Selecting;
+            self.rebuild_preview();
+            return Some(CmdResult::NeedPoint);
+        }
+        let (batch, _) = self.selection_batches.pop()?;
+        for edge in batch {
+            if let Some(index) = self.selected_edges.iter().position(|candidate| *candidate == edge) {
+                self.selected_edges.remove(index);
+            }
+        }
+        if self.selected_edges.is_empty() {
+            self.handle = None;
+            self.base_face = None;
+        }
+        self.last_pick = self
+            .selection_batches
+            .last()
+            .map(|(_, anchor)| *anchor);
+        self.step = EdgeStep::Selecting;
+        self.rebuild_preview();
+        Some(CmdResult::NeedPoint)
+    }
+
     fn wants_text_input(&self) -> bool {
-        self.picked.is_some()
+        matches!(
+            self.step,
+            EdgeStep::Radius
+                | EdgeStep::Expression
+                | EdgeStep::ChamferDistance1
+                | EdgeStep::ChamferDistance2
+        )
     }
 
     fn dyn_commit_as_text(&self) -> bool {
-        self.picked.is_some()
+        matches!(
+            self.step,
+            EdgeStep::Radius | EdgeStep::ChamferDistance1 | EdgeStep::ChamferDistance2
+        )
     }
 
     fn dyn_spec(&self) -> Option<DynSpec> {
-        let (_, pick) = self.picked?;
-        Some(DynSpec {
+        let pick = self.last_pick?;
+        matches!(
+            self.step,
+            EdgeStep::Radius | EdgeStep::ChamferDistance1 | EdgeStep::ChamferDistance2
+        )
+        .then(|| DynSpec {
             anchor: DynAnchor::Point(pick),
             fields: vec![DynFieldSpec::new(match self.operation {
                 EdgeOperation::Fillet => DynRole::Radius,
@@ -137,10 +722,163 @@ impl CadCommand for SolidEdgeCommand {
     }
 
     fn dyn_live_value(&self, cursor: DVec3) -> Option<f64> {
-        self.picked.map(|(_, pick)| cursor.distance(pick))
+        matches!(
+            self.step,
+            EdgeStep::Radius | EdgeStep::ChamferDistance1 | EdgeStep::ChamferDistance2
+        )
+            .then(|| self.last_pick.map(|pick| cursor.distance(pick)))
+            .flatten()
+    }
+
+    fn on_preview_wires(&mut self, cursor: DVec3) -> Vec<WireModel> {
+        if matches!(
+            self.step,
+            EdgeStep::Radius | EdgeStep::ChamferDistance1 | EdgeStep::ChamferDistance2
+        ) {
+            if let Some(value) = self.last_pick.map(|pick| cursor.distance(pick)) {
+                if value > 0.0 && value.is_finite() {
+                    let values = match self.step {
+                        EdgeStep::ChamferDistance2 => (self.default_value, value),
+                        _ => (value, self.other_value),
+                    };
+                    if let Some((handle, wires)) = self.preview_for_values(values.0, values.1) {
+                        self.preview_wires = wires;
+                        self.preview_hidden.clear();
+                        self.preview_hidden.push(handle);
+                    } else {
+                        self.preview_wires.clear();
+                        self.preview_hidden.clear();
+                    }
+                }
+            }
+        }
+        self.preview_wires.clone()
+    }
+
+    fn preview_hidden_handles(&self) -> &[Handle] {
+        &self.preview_hidden
     }
 }
 
+fn edge_loops(body: &Body, seed: EdgeKey) -> Vec<(FaceKey, Vec<EdgeKey>)> {
+    let Some(edge) = body.edges.get(seed) else {
+        return Vec::new();
+    };
+    let mut candidates = Vec::new();
+    for coedge_key in &edge.coedges {
+        let Some(coedge) = body.coedges.get(*coedge_key) else {
+            continue;
+        };
+        let Some(edge_loop) = body.loops.get(coedge.owner) else {
+            continue;
+        };
+        let edges = edge_loop
+            .coedges
+            .iter()
+            .filter_map(|key| body.coedges.get(*key).map(|coedge| coedge.edge))
+            .collect::<Vec<_>>();
+        let candidate = (edge_loop.owner, edges);
+        if !candidate.1.is_empty() && !candidates.contains(&candidate) {
+            candidates.push(candidate);
+        }
+    }
+    candidates
+}
+
+fn edge_belongs_to_face(body: &Body, edge: EdgeKey, face: FaceKey) -> bool {
+    body.edges.get(edge).is_some_and(|edge| {
+        edge.coedges.iter().any(|coedge| {
+            body.coedges
+                .get(*coedge)
+                .and_then(|coedge| body.loops.get(coedge.owner))
+                .is_some_and(|edge_loop| edge_loop.owner == face)
+        })
+    })
+}
+
+fn nearest_edge_face(body: &Body, edge: EdgeKey, point: [f64; 3]) -> Option<FaceKey> {
+    let edge = body.edges.get(edge)?;
+    edge.coedges
+        .iter()
+        .filter_map(|coedge| {
+            let edge_loop = body.loops.get(body.coedges.get(*coedge)?.owner)?;
+            let face = body.faces.get(edge_loop.owner)?;
+            let surface = body.surfaces.get(face.surface)?;
+            let distance = surface.distance_to(point).abs();
+            distance.is_finite().then_some((edge_loop.owner, distance))
+        })
+        .min_by(|first, second| first.1.total_cmp(&second.1))
+        .map(|(face, _)| face)
+}
+
+fn positive_default(value: f64) -> f64 {
+    if value.is_finite() && value > 0.0 {
+        value
+    } else {
+        1.0
+    }
+}
+
+fn edge_chain(body: &Body, seed: EdgeKey) -> Vec<EdgeKey> {
+    let mut chain = vec![seed];
+    let mut next = 0;
+    while next < chain.len() {
+        let current_key = chain[next];
+        next += 1;
+        let Some(current) = body.edges.get(current_key) else {
+            continue;
+        };
+        for vertex in [current.start, current.end] {
+            let Some(current_tangent) = edge_tangent_from_vertex(body, current_key, vertex) else {
+                continue;
+            };
+            for candidate_key in body.edge_keys() {
+                if chain.contains(&candidate_key) {
+                    continue;
+                }
+                let Some(candidate) = body.edges.get(candidate_key) else {
+                    continue;
+                };
+                if candidate.start != vertex && candidate.end != vertex {
+                    continue;
+                }
+                let Some(candidate_tangent) =
+                    edge_tangent_from_vertex(body, candidate_key, vertex)
+                else {
+                    continue;
+                };
+                if current_tangent.dot(candidate_tangent) < -0.999 {
+                    chain.push(candidate_key);
+                }
+            }
+        }
+    }
+    chain
+}
+
+fn edge_tangent_from_vertex(
+    body: &Body,
+    edge_key: EdgeKey,
+    vertex: cadkernel::brep::VertexKey,
+) -> Option<DVec3> {
+    let edge = body.edges.get(edge_key)?;
+    let curve = body.curves.get(edge.curve)?;
+    let span = edge.end_parameter - edge.start_parameter;
+    if !span.is_finite() || span.abs() <= f64::EPSILON {
+        return None;
+    }
+    let step = span * 1.0e-6;
+    let (at, inside) = if edge.start == vertex {
+        (edge.start_parameter, edge.start_parameter + step)
+    } else if edge.end == vertex {
+        (edge.end_parameter, edge.end_parameter - step)
+    } else {
+        return None;
+    };
+    let tangent = DVec3::from(curve.point_at(inside)) - DVec3::from(curve.point_at(at));
+    (tangent.length_squared() > 0.0 && tangent.is_finite()).then(|| tangent.normalize())
+}
+
 inventory::submit!(crate::command::CommandRegistration {
-    names: &["SOLIDFILLET", "SOLIDCHAMFER"]
+    names: &["FILLETEDGE", "SOLIDFILLET", "CHAMFEREDGE", "SOLIDCHAMFER"]
 });

src/modules/model/mod.rs

@@ -5,6 +5,8 @@ pub mod cylinder_cmd;
 pub mod edge_cmd;
 pub mod polysolid_cmd;
 pub mod primitive_cmd;
+pub mod shell_cmd;
+pub mod slice_cmd;
 
 use crate::modules::{CadModule, IconKind, ModuleEvent, RibbonGroup, RibbonItem, ToolDef};
 
@@ -88,8 +90,9 @@ impl CadModule for ModelModule {
                 RibbonGroup {
                     title: "Edges",
                     tools: vec![
-                        RibbonItem::LargeTool(tool("SOLIDFILLET", "Fillet", FILLET_ICON)),
-                        RibbonItem::LargeTool(tool("SOLIDCHAMFER", "Chamfer", CHAMFER_ICON)),
+                        RibbonItem::LargeTool(tool("FILLETEDGE", "Fillet Edge", FILLET_ICON)),
+                        RibbonItem::LargeTool(tool("CHAMFEREDGE", "Chamfer", CHAMFER_ICON)),
+                        RibbonItem::LargeTool(tool("SHELL", "Shell", PRESSPULL_ICON)),
                     ],
                 },
             ]

src/modules/model/shell_cmd.rs

@@ -0,0 +1,308 @@
+use acadrust::Handle;
+use glam::DVec3;
+
+use crate::command::{CadCommand, CmdOption, CmdResult, InputKind, ShellFaceAction};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum ShellStep {
+    SolidEditOption,
+    BodyOption,
+    SelectSolid,
+    RemoveFaces,
+    AddFaces,
+    Distance,
+}
+
+pub struct ShellCommand {
+    entry_name: &'static str,
+    step: ShellStep,
+    target: Option<Handle>,
+    actions: Vec<ShellFaceAction>,
+    default_distance: f64,
+}
+
+impl ShellCommand {
+    pub fn direct(target: Option<Handle>) -> Self {
+        Self {
+            entry_name: "SHELL",
+            step: if target.is_some() {
+                ShellStep::RemoveFaces
+            } else {
+                ShellStep::SelectSolid
+            },
+            target,
+            actions: Vec::new(),
+            default_distance: 1.0,
+        }
+    }
+
+    pub fn solid_edit(target: Option<Handle>) -> Self {
+        Self {
+            entry_name: "SOLIDEDIT",
+            step: ShellStep::SolidEditOption,
+            target,
+            actions: Vec::new(),
+            default_distance: 1.0,
+        }
+    }
+
+    fn finish(&mut self, distance: f64) -> CmdResult {
+        let Some(handle) = self.target else {
+            return CmdResult::Cancel;
+        };
+        CmdResult::SolidShell {
+            handle,
+            actions: std::mem::take(&mut self.actions),
+            distance,
+        }
+    }
+
+    fn undo_face_action(&mut self) -> CmdResult {
+        self.actions.pop();
+        CmdResult::NeedPoint
+    }
+
+    fn face_options(add: bool) -> Vec<CmdOption> {
+        if add {
+            vec![
+                CmdOption::new("Undo", "UNDO"),
+                CmdOption::new("Remove", "REMOVE"),
+                CmdOption::new("ALL", "ALL"),
+            ]
+        } else {
+            vec![
+                CmdOption::new("Undo", "UNDO"),
+                CmdOption::new("Add", "ADD"),
+                CmdOption::new("ALL", "ALL"),
+            ]
+        }
+    }
+}
+
+impl CadCommand for ShellCommand {
+    fn name(&self) -> &'static str {
+        self.entry_name
+    }
+
+    fn prompt(&self) -> String {
+        match self.step {
+            ShellStep::SolidEditOption => {
+                crate::t!("Enter a solid editing option [Body/eXit]:").into_owned()
+            }
+            ShellStep::BodyOption => {
+                crate::t!("Enter a body editing option [Shell/eXit]:").into_owned()
+            }
+            ShellStep::SelectSolid => crate::t!("Select a 3D solid:").into_owned(),
+            ShellStep::RemoveFaces => {
+                crate::t!("Select faces to remove [Undo/Add/ALL] <done>:").into_owned()
+            }
+            ShellStep::AddFaces => {
+                crate::t!("Select faces to add [Undo/Remove/ALL] <done>:").into_owned()
+            }
+            ShellStep::Distance => crate::tf!(
+                "Specify the shell offset distance <{:.3}>:",
+                self.default_distance
+            )
+            .into_owned(),
+        }
+    }
+
+    fn options(&self) -> Vec<CmdOption> {
+        match self.step {
+            ShellStep::SolidEditOption => vec![
+                CmdOption::new("Body", "BODY"),
+                CmdOption::new("eXit", "EXIT"),
+            ],
+            ShellStep::BodyOption => vec![
+                CmdOption::new("Shell", "SHELL"),
+                CmdOption::new("eXit", "EXIT"),
+            ],
+            ShellStep::RemoveFaces => Self::face_options(false),
+            ShellStep::AddFaces => Self::face_options(true),
+            _ => Vec::new(),
+        }
+    }
+
+    fn needs_entity_pick(&self) -> bool {
+        matches!(
+            self.step,
+            ShellStep::SelectSolid | ShellStep::RemoveFaces | ShellStep::AddFaces
+        )
+    }
+
+    fn entity_pick_includes_fills(&self) -> bool {
+        true
+    }
+
+    fn entity_pick_uses_surface_point(&self) -> bool {
+        true
+    }
+
+    fn entity_pick_highlights_hover(&self) -> bool {
+        true
+    }
+
+    fn on_entity_pick(&mut self, handle: Handle, point: DVec3) -> CmdResult {
+        if handle.is_null() {
+            return CmdResult::NeedPoint;
+        }
+        match self.step {
+            ShellStep::SelectSolid => {
+                self.target = Some(handle);
+                self.step = ShellStep::RemoveFaces;
+            }
+            ShellStep::RemoveFaces if self.target == Some(handle) => {
+                self.actions.push(ShellFaceAction::Remove(point));
+            }
+            ShellStep::AddFaces if self.target == Some(handle) => {
+                self.actions.push(ShellFaceAction::Add(point));
+            }
+            _ => {}
+        }
+        CmdResult::NeedPoint
+    }
+
+    fn on_point(&mut self, _point: DVec3) -> CmdResult {
+        CmdResult::NeedPoint
+    }
+
+    fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
+        let value = text.trim();
+        let keyword = value.to_ascii_uppercase();
+        let result = match self.step {
+            ShellStep::SolidEditOption => match keyword.as_str() {
+                "B" | "BODY" => {
+                    self.step = ShellStep::BodyOption;
+                    CmdResult::NeedPoint
+                }
+                "X" | "EXIT" => CmdResult::Cancel,
+                _ => return Some(CmdResult::NeedPoint),
+            },
+            ShellStep::BodyOption => match keyword.as_str() {
+                "S" | "SHELL" => {
+                    self.step = if self.target.is_some() {
+                        ShellStep::RemoveFaces
+                    } else {
+                        ShellStep::SelectSolid
+                    };
+                    CmdResult::NeedPoint
+                }
+                "X" | "EXIT" => CmdResult::Cancel,
+                _ => return Some(CmdResult::NeedPoint),
+            },
+            ShellStep::RemoveFaces => match keyword.as_str() {
+                "U" | "UNDO" => return Some(self.undo_face_action()),
+                "A" | "ADD" => {
+                    self.step = ShellStep::AddFaces;
+                    CmdResult::NeedPoint
+                }
+                "ALL" => {
+                    self.actions.push(ShellFaceAction::RemoveAll);
+                    CmdResult::NeedPoint
+                }
+                _ => return Some(CmdResult::NeedPoint),
+            },
+            ShellStep::AddFaces => match keyword.as_str() {
+                "U" | "UNDO" => return Some(self.undo_face_action()),
+                "R" | "REMOVE" => {
+                    self.step = ShellStep::RemoveFaces;
+                    CmdResult::NeedPoint
+                }
+                "ALL" => {
+                    self.actions.push(ShellFaceAction::AddAll);
+                    CmdResult::NeedPoint
+                }
+                _ => return Some(CmdResult::NeedPoint),
+            },
+            ShellStep::Distance => {
+                let Ok(distance) = value.parse::<f64>() else {
+                    return Some(CmdResult::ReportError(
+                        crate::t!("A numeric shell offset distance is required.").into_owned(),
+                    ));
+                };
+                if !distance.is_finite() || distance.abs() <= f64::EPSILON {
+                    return Some(CmdResult::ReportError(
+                        crate::t!("Value must be nonzero.").into_owned(),
+                    ));
+                }
+                self.default_distance = distance;
+                self.finish(distance)
+            }
+            ShellStep::SelectSolid => return None,
+        };
+        Some(result)
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        match self.step {
+            ShellStep::RemoveFaces | ShellStep::AddFaces => {
+                self.step = ShellStep::Distance;
+                CmdResult::NeedPoint
+            }
+            ShellStep::Distance => self.finish(self.default_distance),
+            _ => CmdResult::Cancel,
+        }
+    }
+
+    fn on_undo_step(&mut self) -> Option<CmdResult> {
+        matches!(self.step, ShellStep::RemoveFaces | ShellStep::AddFaces)
+            .then(|| self.undo_face_action())
+    }
+
+    fn input_kind(&self) -> InputKind {
+        if matches!(self.step, ShellStep::SelectSolid) {
+            InputKind::Point
+        } else {
+            InputKind::SingleToken
+        }
+    }
+}
+
+inventory::submit!(crate::command::CommandRegistration {
+    names: &["SHELL", "SOLIDEDIT"]
+});
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn direct_shell_collects_face_edits_and_signed_distance() {
+        let handle = Handle::new(42);
+        let first = DVec3::new(1.0, 2.0, 3.0);
+        let second = DVec3::new(4.0, 5.0, 6.0);
+        let mut command = ShellCommand::direct(Some(handle));
+
+        command.on_entity_pick(handle, first);
+        command.on_text_input("ADD");
+        command.on_entity_pick(handle, second);
+        command.on_text_input("UNDO");
+        command.on_text_input("ALL");
+        assert!(matches!(command.on_enter(), CmdResult::NeedPoint));
+
+        assert!(matches!(
+            command.on_text_input("-0.5"),
+            Some(CmdResult::SolidShell {
+                handle: result_handle,
+                actions,
+                distance: -0.5,
+            }) if result_handle == handle
+                && actions == vec![ShellFaceAction::Remove(first), ShellFaceAction::AddAll]
+        ));
+    }
+
+    #[test]
+    fn invalid_distance_keeps_the_distance_step_active() {
+        let mut command = ShellCommand::direct(Some(Handle::new(7)));
+        command.on_enter();
+
+        assert!(matches!(
+            command.on_text_input("zero"),
+            Some(CmdResult::ReportError(_))
+        ));
+        assert!(matches!(
+            command.on_text_input("0.25"),
+            Some(CmdResult::SolidShell { distance: 0.25, .. })
+        ));
+    }
+}

src/modules/model/slice_cmd.rs

@@ -0,0 +1,510 @@
+use acadrust::{EntityType, Handle};
+use cadkernel::space::Plane;
+use glam::DVec3;
+
+use crate::command::{CadCommand, CmdOption, CmdResult, SelectionEntity, WorkingPlane};
+use crate::scene::model::wire_model::WireModel;
+
+#[derive(Clone, Copy)]
+enum PlaneKind {
+    Xy,
+    Yz,
+    Zx,
+    View,
+}
+
+enum Step {
+    Targets,
+    FirstPoint,
+    ThreeFirst,
+    ThreeSecond(DVec3),
+    ThirdPoint(DVec3, DVec3),
+    AxisFirst,
+    AxisSecond(DVec3),
+    PlanePoint(PlaneKind),
+    PickObject,
+    PickSurface,
+    Side(Plane),
+    SurfaceSide,
+}
+
+/// Interactive front-end for plane-based SLICE.
+pub struct SliceCommand {
+    step: Step,
+    targets: Vec<Handle>,
+    selected: Vec<Handle>,
+    working: WorkingPlane,
+    view_normal: DVec3,
+    preview_center: DVec3,
+    preview_radius: f64,
+    picked: Option<EntityType>,
+    surface_tool: Option<cadkernel::brep::Body>,
+    notice: Option<&'static str>,
+}
+
+impl SliceCommand {
+    pub fn new(
+        targets: Vec<Handle>,
+        view_normal: DVec3,
+        preview_center: DVec3,
+        preview_radius: f64,
+    ) -> Self {
+        let step = if targets.is_empty() { Step::Targets } else { Step::FirstPoint };
+        Self {
+            step,
+            targets,
+            selected: Vec::new(),
+            working: WorkingPlane::default(),
+            view_normal: view_normal.normalize_or(DVec3::Z),
+            preview_center,
+            preview_radius: preview_radius.max(1.0),
+            picked: None,
+            surface_tool: None,
+            notice: None,
+        }
+    }
+
+    fn plane(origin: DVec3, x: DVec3, normal: DVec3) -> Option<Plane> {
+        Plane::orthonormal(origin.to_array(), x.to_array(), normal.to_array())
+    }
+
+    fn enter_side(&mut self, plane: Plane) -> CmdResult {
+        self.notice = None;
+        self.step = Step::Side(plane);
+        CmdResult::NeedPoint
+    }
+
+    fn finish(&mut self, keep_point: Option<DVec3>) -> CmdResult {
+        let Step::Side(plane) = self.step else {
+            return CmdResult::NeedPoint;
+        };
+        CmdResult::SliceEntities {
+            targets: std::mem::take(&mut self.targets),
+            plane,
+            keep_point,
+        }
+    }
+
+    fn picked_plane(&self) -> Option<Plane> {
+        let entity = self.picked.as_ref()?;
+        if !matches!(
+            entity,
+            EntityType::Arc(_)
+                | EntityType::Circle(_)
+                | EntityType::Ellipse(_)
+                | EntityType::Spline(_)
+                | EntityType::LwPolyline(_)
+                | EntityType::Polyline(_)
+        ) {
+            return None;
+        }
+        crate::scene::model::presspull_model::profile_geometry(entity)
+            .map(|(plane, _, _)| plane)
+    }
+
+    fn finish_surface(&mut self, keep_point: Option<DVec3>) -> CmdResult {
+        let Some(cutter) = self.surface_tool.take() else {
+            return CmdResult::NeedPoint;
+        };
+        CmdResult::SliceSurfaceEntities {
+            targets: std::mem::take(&mut self.targets),
+            cutter: Box::new(cutter),
+            keep_point,
+        }
+    }
+
+    fn plane_at(&self, point: DVec3, kind: PlaneKind) -> Option<Plane> {
+        let (x, normal) = match kind {
+            PlaneKind::Xy => (self.working.x, self.working.z),
+            PlaneKind::Yz => (self.working.y, self.working.x),
+            PlaneKind::Zx => (self.working.z, self.working.y),
+            PlaneKind::View => {
+                let candidate = if self.working.x.dot(self.view_normal).abs() < 0.98 {
+                    self.working.x
+                } else {
+                    self.working.y
+                };
+                (candidate, self.view_normal)
+            }
+        };
+        Self::plane(point, x, normal)
+    }
+}
+
+impl CadCommand for SliceCommand {
+    fn name(&self) -> &'static str {
+        "SLICE"
+    }
+
+    fn prompt(&self) -> String {
+        if let Some(notice) = self.notice {
+            return crate::t!(notice).into_owned();
+        }
+        match self.step {
+            Step::Targets => crate::t!(
+                "SLICE  Select solids or surfaces to slice, then press Enter:"
+            )
+            .into_owned(),
+            Step::FirstPoint => crate::t!(
+                "SLICE  Specify first point on slicing plane or [planar Object/Surface/Zaxis/View/XY/YZ/ZX/3points] <3points>:"
+            )
+            .into_owned(),
+            Step::ThreeFirst => {
+                crate::t!("SLICE  Specify first point on slicing plane:").into_owned()
+            }
+            Step::ThreeSecond(_) => {
+                crate::t!("SLICE  Specify second point on slicing plane:").into_owned()
+            }
+            Step::ThirdPoint(_, _) => {
+                crate::t!("SLICE  Specify third point on slicing plane:").into_owned()
+            }
+            Step::AxisFirst => {
+                crate::t!("SLICE  Specify a point on the slicing plane:").into_owned()
+            }
+            Step::AxisSecond(_) => {
+                crate::t!("SLICE  Specify a point on the plane's normal axis:").into_owned()
+            }
+            Step::PlanePoint(PlaneKind::View) => {
+                crate::t!("SLICE  Specify a point on the current view plane:").into_owned()
+            }
+            Step::PlanePoint(_) => {
+                crate::t!("SLICE  Specify a point on the current UCS plane:").into_owned()
+            }
+            Step::PickObject => crate::t!("SLICE  Select a planar curve object:").into_owned(),
+            Step::PickSurface => crate::t!("SLICE  Select a cutting surface:").into_owned(),
+            Step::Side(_) => crate::t!(
+                "SLICE  Specify a point on the desired side or [Both] <Both>:"
+            )
+            .into_owned(),
+            Step::SurfaceSide => crate::t!(
+                "SLICE  Select a sliced object to keep or [Both] <Both>:"
+            )
+            .into_owned(),
+        }
+    }
+
+    fn options(&self) -> Vec<CmdOption> {
+        match self.step {
+            Step::FirstPoint => vec![
+                CmdOption::new(crate::t!("planar Object").as_ref(), "O"),
+                CmdOption::new(crate::t!("Surface").as_ref(), "S"),
+                CmdOption::new(crate::t!("Zaxis").as_ref(), "Z"),
+                CmdOption::new(crate::t!("View").as_ref(), "V"),
+                CmdOption::new("XY", "XY"),
+                CmdOption::new("YZ", "YZ"),
+                CmdOption::new("ZX", "ZX"),
+                CmdOption::new(crate::t!("3points").as_ref(), "3"),
+            ],
+            Step::Side(_) | Step::SurfaceSide => {
+                vec![CmdOption::new(crate::t!("Both").as_ref(), "B")]
+            }
+            _ => Vec::new(),
+        }
+    }
+
+    fn set_working_plane(&mut self, plane: WorkingPlane) {
+        self.working = plane;
+    }
+
+    fn on_point(&mut self, point: DVec3) -> CmdResult {
+        self.notice = None;
+        match self.step {
+            Step::FirstPoint => {
+                self.step = Step::ThreeSecond(point);
+                CmdResult::NeedPoint
+            }
+            Step::ThreeFirst => {
+                self.step = Step::ThreeSecond(point);
+                CmdResult::NeedPoint
+            }
+            Step::ThreeSecond(first) => {
+                self.step = Step::ThirdPoint(first, point);
+                CmdResult::NeedPoint
+            }
+            Step::ThirdPoint(first, second) => {
+                let x = second - first;
+                let normal = x.cross(point - first);
+                Self::plane(first, x, normal)
+                    .map_or(CmdResult::NeedPoint, |plane| self.enter_side(plane))
+            }
+            Step::AxisFirst => {
+                self.step = Step::AxisSecond(point);
+                CmdResult::NeedPoint
+            }
+            Step::AxisSecond(origin) => {
+                let normal = point - origin;
+                let x = if self.working.x.dot(normal.normalize_or(DVec3::Z)).abs() < 0.98 {
+                    self.working.x
+                } else {
+                    self.working.y
+                };
+                Self::plane(origin, x, normal)
+                    .map_or(CmdResult::NeedPoint, |plane| self.enter_side(plane))
+            }
+            Step::PlanePoint(kind) => self
+                .plane_at(point, kind)
+                .map_or(CmdResult::NeedPoint, |plane| self.enter_side(plane)),
+            Step::Side(_) => self.finish(Some(point)),
+            Step::SurfaceSide => self.finish_surface(Some(point)),
+            _ => CmdResult::NeedPoint,
+        }
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        match self.step {
+            Step::Targets if !self.selected.is_empty() => {
+                self.targets = std::mem::take(&mut self.selected);
+                self.step = Step::FirstPoint;
+                CmdResult::DeselectAndContinue
+            }
+            Step::FirstPoint => {
+                self.step = Step::ThreeFirst;
+                CmdResult::NeedPoint
+            }
+            Step::Side(_) => self.finish(None),
+            Step::SurfaceSide => self.finish_surface(None),
+            _ => CmdResult::NeedPoint,
+        }
+    }
+
+    fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
+        let keyword = text.trim().to_ascii_uppercase();
+        Some(match self.step {
+            Step::FirstPoint => match keyword.as_str() {
+                "O" | "OBJECT" => {
+                    self.step = Step::PickObject;
+                    CmdResult::NeedPoint
+                }
+                "S" | "SURFACE" => {
+                    self.step = Step::PickSurface;
+                    CmdResult::NeedPoint
+                }
+                "Z" | "ZAXIS" => {
+                    self.step = Step::AxisFirst;
+                    CmdResult::NeedPoint
+                }
+                "V" | "VIEW" => {
+                    self.step = Step::PlanePoint(PlaneKind::View);
+                    CmdResult::NeedPoint
+                }
+                "XY" => {
+                    self.step = Step::PlanePoint(PlaneKind::Xy);
+                    CmdResult::NeedPoint
+                }
+                "YZ" => {
+                    self.step = Step::PlanePoint(PlaneKind::Yz);
+                    CmdResult::NeedPoint
+                }
+                "ZX" | "XZ" => {
+                    self.step = Step::PlanePoint(PlaneKind::Zx);
+                    CmdResult::NeedPoint
+                }
+                "3" | "3P" | "3POINTS" => {
+                    self.step = Step::ThreeFirst;
+                    CmdResult::NeedPoint
+                }
+                _ => CmdResult::NeedPoint,
+            },
+            Step::Side(_) if matches!(keyword.as_str(), "" | "B" | "BOTH") => self.finish(None),
+            Step::SurfaceSide if matches!(keyword.as_str(), "" | "B" | "BOTH") => {
+                self.finish_surface(None)
+            }
+            _ => CmdResult::NeedPoint,
+        })
+    }
+
+    fn point_step_accepts_keywords(&self) -> bool {
+        matches!(self.step, Step::FirstPoint | Step::Side(_) | Step::SurfaceSide)
+    }
+
+    fn is_selection_gathering(&self) -> bool {
+        matches!(self.step, Step::Targets)
+    }
+
+    fn selection_forces_add(&self) -> bool {
+        true
+    }
+
+    fn inject_selection_entities(&mut self, entities: Vec<SelectionEntity>) {
+        self.selected = entities
+            .into_iter()
+            .filter_map(|item| {
+                matches!(item.entity, EntityType::Solid3D(_) | EntityType::Surface(_))
+                    .then_some(item.handle)
+            })
+            .collect();
+    }
+
+    fn on_selection_complete(&mut self, _handles: Vec<Handle>) -> CmdResult {
+        CmdResult::NeedPoint
+    }
+
+    fn needs_entity_pick(&self) -> bool {
+        matches!(
+            self.step,
+            Step::PickObject | Step::PickSurface | Step::SurfaceSide
+        )
+    }
+
+    fn entity_pick_highlights_hover(&self) -> bool {
+        self.needs_entity_pick()
+    }
+
+    fn inject_before_entity_pick(&self) -> bool {
+        matches!(self.step, Step::PickObject | Step::PickSurface)
+    }
+
+    fn entity_pick_uses_surface_point(&self) -> bool {
+        matches!(self.step, Step::SurfaceSide)
+    }
+
+    fn inject_picked_entity(&mut self, entity: EntityType) {
+        self.picked = Some(entity);
+    }
+
+    fn on_entity_pick(&mut self, _handle: Handle, _point: DVec3) -> CmdResult {
+        if matches!(self.step, Step::SurfaceSide) {
+            return self.finish_surface(Some(_point));
+        }
+        let surface_only = matches!(self.step, Step::PickSurface);
+        if surface_only {
+            let body = self.picked.as_ref().and_then(|entity| match entity {
+                EntityType::Surface(surface) => {
+                    crate::scene::convert::solid3d_tess::kernel_surface_body(surface)
+                }
+                _ => None,
+            });
+            if let Some(body) = body {
+                if let Some(plane) = planar_body_plane(&body) {
+                    return self.enter_side(plane);
+                }
+                if body.face_keys().count() == 1 {
+                    self.surface_tool = Some(body);
+                    self.notice = None;
+                    self.step = Step::SurfaceSide;
+                    return CmdResult::NeedPoint;
+                }
+            }
+            self.notice = Some(
+                "SLICE  The selected surface does not define one supported cutting sheet. Select another surface:",
+            );
+            return CmdResult::NeedPoint;
+        }
+        match self.picked_plane() {
+            Some(plane) => self.enter_side(plane),
+            None => {
+                self.notice = Some(
+                    "SLICE  The selected object does not define a plane. Select a planar curve object:",
+                );
+                CmdResult::NeedPoint
+            }
+        }
+    }
+
+    fn on_preview_wires(&mut self, point: DVec3) -> Vec<WireModel> {
+        let mut wires = Vec::new();
+        let plane = match self.step {
+            Step::ThirdPoint(first, second) => {
+                wires.push(WireModel::solid_f64(
+                    "slice_triangle".into(),
+                    vec![
+                        first.to_array(),
+                        second.to_array(),
+                        point.to_array(),
+                        first.to_array(),
+                    ],
+                    WireModel::CYAN,
+                    false,
+                ));
+                Self::plane(first, second - first, (second - first).cross(point - first))
+            }
+            Step::AxisSecond(origin) => {
+                wires.push(WireModel::solid_f64(
+                    "slice_normal".into(),
+                    vec![origin.to_array(), point.to_array()],
+                    WireModel::CYAN,
+                    false,
+                ));
+                let normal = point - origin;
+                let x = if self.working.x.dot(normal.normalize_or(DVec3::Z)).abs() < 0.98 {
+                    self.working.x
+                } else {
+                    self.working.y
+                };
+                Self::plane(origin, x, normal)
+            }
+            Step::PlanePoint(kind) => self.plane_at(point, kind),
+            Step::Side(plane) => Some(plane),
+            _ => None,
+        };
+        if let Some(plane) = plane {
+            wires.extend(plane_grid(
+                plane,
+                self.preview_center,
+                self.preview_radius,
+            ));
+        }
+        wires
+    }
+}
+
+fn planar_body_plane(body: &cadkernel::brep::Body) -> Option<Plane> {
+    let mut faces = body.face_keys();
+    let first = cadkernel::brep::planar_face_profile(body, faces.next()?)?.plane;
+    let normal = DVec3::from_array(first.normal()?);
+    let tolerance = cadkernel::brep::operation_tolerance(&[body]);
+    faces
+        .all(|face| {
+            let Some(profile) = cadkernel::brep::planar_face_profile(body, face) else {
+                return false;
+            };
+            profile.plane.normal().is_some_and(|other| {
+                normal.dot(DVec3::from_array(other)).abs() >= 1.0 - 1e-9
+                    && first
+                        .distance_to(profile.plane.origin)
+                        .is_some_and(|gap| gap.abs() <= tolerance * 4.0)
+            })
+        })
+        .then_some(first)
+}
+
+fn plane_grid(plane: Plane, centre: DVec3, radius: f64) -> Vec<WireModel> {
+    let normal = DVec3::from_array(plane.normal().unwrap_or([0.0, 0.0, 1.0]));
+    let projected = centre
+        - normal
+            * plane
+                .distance_to(centre.to_array())
+                .unwrap_or_default();
+    let x = DVec3::from_array(plane.x_axis);
+    let y = DVec3::from_array(plane.y_axis);
+    let color = [0.2, 0.55, 1.0, 1.0];
+    (-5..=5)
+        .flat_map(|index| {
+            let offset = radius * index as f64 / 5.0;
+            [
+                WireModel::solid_f64(
+                    format!("slice_grid_x_{index}"),
+                    vec![
+                        (projected + x * offset - y * radius).to_array(),
+                        (projected + x * offset + y * radius).to_array(),
+                    ],
+                    color,
+                    false,
+                ),
+                WireModel::solid_f64(
+                    format!("slice_grid_y_{index}"),
+                    vec![
+                        (projected + y * offset - x * radius).to_array(),
+                        (projected + y * offset + x * radius).to_array(),
+                    ],
+                    color,
+                    false,
+                ),
+            ]
+        })
+        .collect()
+}
+
+inventory::submit!(crate::command::CommandRegistration {
+    names: &["SLICE", "SL"]
+});