feat(scene): render 3D surface entities (loft/sweep/extrude/etc.)

ACAD_SURFACE entities now load and render. Their NURBS faces are
tessellated by building a truck BSplineSurface from the ACIS `spline-surface`
control net and knot vectors, then sampling its parametric grid — reusing the
same NURBS kernel the Model tab already builds on. Analytic faces
(plane/cone/sphere/torus) continue through the existing tessellator.

- New spline_tess.rs: parse the ACIS `nubs` block (degrees, knots with the
  clamped end-multiplicity fix, control grid) into a truck BSplineSurface and
  mesh it.
- tessellate_surface + Surface wired through the mesh-build, fallback-wire,
  and entity-classification paths.
- Bump acadrust to the commit that adds the Surface entity.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

Cargo.lock

@@ -56,7 +56,7 @@ checksum = "366ffbaa4442f4684d91e2cd7c5ea7c4ed8add41959a31447066e279e432b618"
 [[package]]
 name = "acadrust"
 version = "0.3.4"
-source = "git+https://github.com/HakanSeven12/acadrust?branch=main#b4ab9ffedfae44b5731301a94c849a3c8f695105"
+source = "git+https://github.com/HakanSeven12/acadrust?branch=main#3e2afad2d0baf03be584c28111040e13870b9e70"
 dependencies = [
  "ahash",
  "anyhow",
@@ -3178,7 +3178,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b577e2d69827c4740cba2b52efaad1c4cc7c73042860b199710b3575c68438d"
 dependencies = [
  "bytecount",
- "memchr 1.0.2",
+ "memchr 2.8.1",
  "nom 8.0.0",
 ]
 

src/app/helpers.rs

@@ -245,6 +245,7 @@ pub(super) fn entity_type_key(entity: &acadrust::EntityType) -> String {
         Solid3D(_) => "solid3d",
         Region(_) => "region",
         Body(_) => "body",
+        Surface(_) => "surface",
         Mesh(_) => "mesh",
         Ray(_) => "ray",
         XLine(_) => "xline",

src/entities/names.rs

@@ -39,6 +39,7 @@ pub fn ui_name(e: &EntityType) -> &'static str {
         EntityType::Solid3D(_) => "3D Solid",
         EntityType::Region(_) => "Region",
         EntityType::Body(_) => "Body",
+        EntityType::Surface(_) => "Surface",
         EntityType::Mesh(_) => "Mesh",
         EntityType::Ray(_) => "Ray",
         EntityType::XLine(_) => "XLine",

src/entities/solid3d.rs

@@ -282,6 +282,7 @@ pub fn fallback_wires(e: &EntityType) -> Option<&[acadrust::entities::Wire]> {
         EntityType::Solid3D(s) => Some(&s.wires),
         EntityType::Region(r) => Some(&r.wires),
         EntityType::Body(b) => Some(&b.wires),
+        EntityType::Surface(s) => Some(&s.wires),
         _ => None,
     }
 }
@@ -293,6 +294,7 @@ pub fn tessellate_volume(e: &EntityType, color: [f32; 4], facet_res: f64) -> Opt
         EntityType::Solid3D(s) => solid3d_tess::tessellate_solid3d(s, color, facet_res),
         EntityType::Region(r) => solid3d_tess::tessellate_region(r, color, facet_res),
         EntityType::Body(b) => solid3d_tess::tessellate_body(b, color, facet_res),
+        EntityType::Surface(s) => solid3d_tess::tessellate_surface(s, color, facet_res),
         _ => None,
     }
 }

src/entities/traits.rs

@@ -129,6 +129,7 @@ pub fn entity_type_name(et: &EntityType) -> &'static str {
         EntityType::Solid3D(_) => "Solid3D",
         EntityType::Region(_) => "Region",
         EntityType::Body(_) => "Body",
+        EntityType::Surface(_) => "Surface",
         EntityType::Table(_) => "Table",
         EntityType::Tolerance(_) => "Tolerance",
         EntityType::PolyfaceMesh(_) => "PolyfaceMesh",

src/scene/mod.rs

@@ -26,6 +26,7 @@ pub(super) struct EntityIndex {
 pub(crate) mod render;
 mod selection;
 pub mod solid3d_tess;
+pub mod spline_tess;
 pub mod tess_util;
 pub mod tessellate;
 pub mod transform;
@@ -185,7 +186,7 @@ pub fn build_derived_caches(doc: &CadDocument) -> DerivedCaches {
         match e {
             EntityType::Hatch(_) | EntityType::Solid(_) => hatch_handles.push(h),
             EntityType::RasterImage(_) => image_handles.push(h),
-            EntityType::Solid3D(_) | EntityType::Region(_) | EntityType::Body(_) => {
+            EntityType::Solid3D(_) | EntityType::Region(_) | EntityType::Body(_) | EntityType::Surface(_) => {
                 mesh_handles.push(h)
             }
             _ => {}
@@ -1839,7 +1840,7 @@ impl Scene {
             // draw-order biasing so 3D occlusion is never flattened.
             if matches!(
                 e,
-                EntityType::Solid3D(_) | EntityType::Region(_) | EntityType::Body(_)
+                EntityType::Solid3D(_) | EntityType::Region(_) | EntityType::Body(_) | EntityType::Surface(_)
             ) {
                 continue;
             }
@@ -3448,7 +3449,7 @@ impl Scene {
         let facet_res = self.document.header.facet_resolution;
         let mesh_seed = if matches!(
             &entity,
-            EntityType::Solid3D(_) | EntityType::Region(_) | EntityType::Body(_)
+            EntityType::Solid3D(_) | EntityType::Region(_) | EntityType::Body(_) | EntityType::Surface(_)
         ) {
             let color = self.render_style(&entity).0;
             let woff = self.world_offset;
@@ -4320,7 +4321,7 @@ impl Scene {
             .document
             .entities()
             .filter_map(|e| match e {
-                EntityType::Solid3D(_) | EntityType::Region(_) | EntityType::Body(_) => {
+                EntityType::Solid3D(_) | EntityType::Region(_) | EntityType::Body(_) | EntityType::Surface(_) => {
                     let color = self.render_style(e).0;
                     Some((e.common().handle, e.clone(), color))
                 }
@@ -7002,6 +7003,7 @@ fn tessellate_entity(
                                 | EntityType::PolygonMesh(_)
                                 | EntityType::Body(_)
                                 | EntityType::Region(_)
+                                | EntityType::Surface(_)
                         );
                         if !is_text && w_px.max(h_px) / wpp < 5.0 {
                             // Sub-pixel entity: emit a stub instead of

src/scene/solid3d_tess.rs

@@ -106,6 +106,16 @@ fn tessellate_sat(
                     tess_torus_face(&torus, lod, &mut verts, &mut normals, &mut indices);
                 }
             }
+            "spline-surface" => {
+                crate::scene::spline_tess::tess_spline_face(
+                    sat,
+                    &face,
+                    lod,
+                    &mut verts,
+                    &mut normals,
+                    &mut indices,
+                );
+            }
             _ => {}
         }
     }
@@ -255,6 +265,24 @@ pub fn tessellate_body(body: &Body, color: [f32; 4], facet_res: f64) -> Option<M
     tessellate_sat_lods(&sat, name, color, facet_res)
 }
 
+/// Tessellate a `Surface` entity (ACAD_SURFACE family) at all three LOD
+/// levels. Surfaces are ACIS-backed just like bodies, so the same SAT/SAB
+/// path applies — including the B-spline `spline-surface` faces that loft /
+/// sweep / revolve produce.
+pub fn tessellate_surface(
+    surface: &acadrust::entities::Surface,
+    color: [f32; 4],
+    facet_res: f64,
+) -> Option<MeshLodSet> {
+    let sat = parse_acis(
+        || surface.parse_sat(),
+        surface.acis_data.is_binary,
+        &surface.acis_data.sab_data,
+    )?;
+    let name = surface.common.handle.value().to_string();
+    tessellate_sat_lods(&sat, name, color, facet_res)
+}
+
 /// Tessellate a `Solid3D` entity at all three LOD levels.
 ///
 /// Returns `None` when the entity has no parseable SAT data or produces no

src/scene/spline_tess.rs

@@ -0,0 +1,190 @@
+// B-spline (NURBS) surface tessellation for ACIS `spline-surface` faces.
+//
+// Lofted / swept / revolved surfaces store their geometry as an ACIS
+// `nubs` (non-uniform B-spline) block inside the `spline-surface` record.
+// Rather than evaluate the basis functions by hand, we parse the control net
+// and knot vectors out of the SAT tokens, hand them to truck's
+// `BSplineSurface` (the same NURBS kernel the Model tab already builds on),
+// and sample its parametric grid into triangles.
+
+use acadrust::entities::acis::{SatDocument, SatFace, SatRecord, SatToken};
+use truck_modeling::{BSplineSurface, KnotVec, ParametricSurface, ParametricSurface3D, Point3};
+
+use crate::scene::solid3d_tess::LodConfig;
+
+/// Tessellate one `spline-surface` face by sampling its B-spline surface.
+/// Appends triangles to the shared mesh buffers; a no-op when the surface
+/// record can't be parsed into a B-spline.
+pub fn tess_spline_face(
+    sat: &SatDocument,
+    face: &SatFace,
+    lod: LodConfig,
+    verts: &mut Vec<[f32; 3]>,
+    normals: &mut Vec<[f32; 3]>,
+    indices: &mut Vec<u32>,
+) {
+    let Some(surf_rec) = sat.resolve(face.surface()) else {
+        return;
+    };
+    let Some(surface) = build_bspline_surface(surf_rec) else {
+        return;
+    };
+
+    // Sample over the knot domain. The B-spline patches stored by loft/sweep
+    // are already trimmed to the face, so the full parametric rectangle is the
+    // visible surface — no separate boundary trim needed.
+    let (u_range, v_range) = surface.parameter_range();
+    let (u0, u1) = range_bounds(u_range);
+    let (v0, v1) = range_bounds(v_range);
+    if !(u1 > u0) || !(v1 > v0) {
+        return;
+    }
+
+    let su = lod.grid_u.max(8);
+    let sv = lod.grid_v.max(8);
+
+    let base = verts.len() as u32;
+    for j in 0..=sv {
+        let v = v0 + (v1 - v0) * (j as f64 / sv as f64);
+        for i in 0..=su {
+            let u = u0 + (u1 - u0) * (i as f64 / su as f64);
+            let p = surface.subs(u, v);
+            let n = surface.normal(u, v);
+            verts.push([p.x as f32, p.y as f32, p.z as f32]);
+            normals.push([n.x as f32, n.y as f32, n.z as f32]);
+        }
+    }
+
+    let row = (su + 1) as u32;
+    for j in 0..sv as u32 {
+        for i in 0..su as u32 {
+            let a = base + j * row + i;
+            let b = a + 1;
+            let c = a + row;
+            let d = c + 1;
+            indices.extend_from_slice(&[a, b, d, a, d, c]);
+        }
+    }
+}
+
+/// Extract the inclusive `[start, end]` bounds from a truck parameter range.
+fn range_bounds(r: (std::ops::Bound<f64>, std::ops::Bound<f64>)) -> (f64, f64) {
+    use std::ops::Bound::*;
+    let lo = match r.0 {
+        Included(v) | Excluded(v) => v,
+        Unbounded => 0.0,
+    };
+    let hi = match r.1 {
+        Included(v) | Excluded(v) => v,
+        Unbounded => 1.0,
+    };
+    (lo, hi)
+}
+
+/// Parse the `nubs` control net + knot vectors out of a `spline-surface`
+/// record's token stream into a truck `BSplineSurface`.
+fn build_bspline_surface(rec: &SatRecord) -> Option<BSplineSurface<Point3>> {
+    let toks = &rec.tokens;
+    // Locate the real B-spline block. `nullbs` placeholders (for absent
+    // rail/path surfaces) precede it; the actual surface is `nubs`.
+    let start = toks.iter().position(|t| {
+        matches!(t, SatToken::Ident(s) if s == "nubs" || s == "nurbs")
+    })?;
+
+    let mut p = start + 1;
+    let deg_u = read_int(toks, &mut p)? as usize;
+    let deg_v = read_int(toks, &mut p)? as usize;
+    // Four form flags (closure / singularity in u and v) — skip.
+    for _ in 0..4 {
+        read_int(toks, &mut p)?;
+    }
+    let n_uknot = read_int(toks, &mut p)? as usize;
+    let n_vknot = read_int(toks, &mut p)? as usize;
+
+    let u_knots = read_knot_vec(toks, &mut p, n_uknot, deg_u)?;
+    let v_knots = read_knot_vec(toks, &mut p, n_vknot, deg_v)?;
+
+    let n_ctrl_u = u_knots.len().checked_sub(deg_u + 1)?;
+    let n_ctrl_v = v_knots.len().checked_sub(deg_v + 1)?;
+    if n_ctrl_u == 0 || n_ctrl_v == 0 {
+        return None;
+    }
+
+    // Control points are stored row-major with u varying fastest (a full row
+    // of u control points per v step). truck wants `ctrl[i_u][j_v]`.
+    let total = n_ctrl_u * n_ctrl_v;
+    let mut flat: Vec<Point3> = Vec::with_capacity(total);
+    for _ in 0..total {
+        let x = read_float(toks, &mut p)?;
+        let y = read_float(toks, &mut p)?;
+        let z = read_float(toks, &mut p)?;
+        flat.push(Point3::new(x, y, z));
+    }
+    let mut ctrl = vec![Vec::with_capacity(n_ctrl_v); n_ctrl_u];
+    for v in 0..n_ctrl_v {
+        for u in 0..n_ctrl_u {
+            ctrl[u].push(flat[v * n_ctrl_u + u]);
+        }
+    }
+
+    let uk = KnotVec::from(u_knots);
+    let vk = KnotVec::from(v_knots);
+    BSplineSurface::try_new((uk, vk), ctrl).ok()
+}
+
+/// Read `count` `(knot value, multiplicity)` pairs into an expanded knot
+/// vector. ACIS stores the end knots with multiplicity = degree; a clamped
+/// B-spline needs degree + 1, so the first and last multiplicities are bumped
+/// by one.
+fn read_knot_vec(
+    toks: &[SatToken],
+    p: &mut usize,
+    count: usize,
+    degree: usize,
+) -> Option<Vec<f64>> {
+    let mut knots: Vec<f64> = Vec::new();
+    for i in 0..count {
+        let value = read_float(toks, p)?;
+        let mut mult = read_int(toks, p)? as usize;
+        if i == 0 || i == count - 1 {
+            mult += 1;
+        }
+        let _ = degree;
+        for _ in 0..mult {
+            knots.push(value);
+        }
+    }
+    if knots.len() < 2 {
+        return None;
+    }
+    Some(knots)
+}
+
+fn read_int(toks: &[SatToken], p: &mut usize) -> Option<i64> {
+    while *p < toks.len() {
+        let t = &toks[*p];
+        *p += 1;
+        match t {
+            SatToken::Integer(v) => return Some(*v),
+            SatToken::Float(v) => return Some(*v as i64),
+            // Skip block delimiters / idents that may appear inline.
+            SatToken::Ident(_) | SatToken::Enum(_) => continue,
+            _ => return None,
+        }
+    }
+    None
+}
+
+fn read_float(toks: &[SatToken], p: &mut usize) -> Option<f64> {
+    while *p < toks.len() {
+        let t = &toks[*p];
+        *p += 1;
+        match t {
+            SatToken::Float(v) => return Some(*v),
+            SatToken::Integer(v) => return Some(*v as f64),
+            SatToken::Ident(_) | SatToken::Enum(_) => continue,
+            _ => return None,
+        }
+    }
+    None
+}

src/scene/tessellate.rs

@@ -617,7 +617,10 @@ fn fallback_geometry(entity: &EntityType, world_offset: [f64; 3]) -> Geometry {
         // plus an insertion snap — never the placeholder segment below, which
         // would otherwise draw a stray 1-unit line at the origin next to the
         // solid.
-        EntityType::Solid3D(_) | EntityType::Region(_) | EntityType::Body(_) => {
+        EntityType::Solid3D(_)
+        | EntityType::Region(_)
+        | EntityType::Body(_)
+        | EntityType::Surface(_) => {
             let pts = solid_wire_fallback(entity, world_offset);
             let mut snap = vec![];
             if let Some(p) = crate::entities::solid3d::point_of_reference(entity) {