fix: faces a sheet fold moves keep their names (#535) (#585)

Faces that a sheet fold or unfold moves keep their names: points on a moved panel are taken back through the panel they lie on to where the sheet held them before the feature, and named from the faces there. Un-ignores the #535 regression test. Fixes #535.

Co-authored-by: jonaswre <[email protected]>

crates/doc/src/config_shell_tests.rs

@@ -253,6 +253,7 @@ fn saved_former_strip_projection_reports_lost_without_expanding_healthy_material
         before,
         depth: 1,
         mats: vec![],
+        sheets: vec![],
     })));
     let captured = crate::naming::face_name_at_body(&old_body, Vec3::new(20., 6., 1.)).unwrap();
     assert_eq!(crate::naming::parent_piece(&captured), Some(stem.as_str()), "actual strip capture records a piece name");
@@ -376,6 +377,7 @@ fn saved_curved_strip_projection_is_lost_after_exact_wall_coalescence() {
         before,
         depth: 1,
         mats: vec![],
+        sheets: vec![],
     })));
     let t = std::f64::consts::FRAC_1_SQRT_2;
     let at = Vec3::new(34. + 6. * t, 24. + 6. * t, 1.);
@@ -515,6 +517,7 @@ fn saved_stepped_tab_cut_piece_projection_is_lost_without_expanding_material() {
         before,
         depth: 1,
         mats: vec![],
+        sheets: vec![],
     })));
     let at = Vec3::new(0., 15., 1.);
     let former = crate::naming::face_name_at_body(&old_body, at).unwrap();

crates/doc/src/eval.rs

@@ -364,7 +364,8 @@ impl ModelState {
     fn stamp(&mut self, before: &Arc<ModelState>, f: &Feature, key: u64, mats: Vec<Mat>) {
         let feature = f.id;
         let depth = before.bodies.iter().filter_map(|b| b.names.origin.as_ref().map(|o| o.depth)).max().unwrap_or(0) + 1;
-        let origin = Arc::new(crate::naming::NamingOrigin { feature: f.clone(), before: before.clone(), depth, mats });
+        let sheets = if f.kind.is_sheet() { self.sheets.clone() } else { Vec::new() };
+        let origin = Arc::new(crate::naming::NamingOrigin { feature: f.clone(), before: before.clone(), depth, mats, sheets });
         // Pieces a cut left are named after their faces, not the kernel's shell order (unless
         // the feature was saved when they were named in that order).
         if !f.shell_piece_order {

crates/doc/src/naming.rs

@@ -31,6 +31,8 @@ pub struct NamingOrigin {
     pub depth: usize,
     /// Instance transforms of a pattern or mirror (its copies are named after their sources).
     pub mats: Vec<crate::Mat>,
+    /// The sheet metal bodies after a sheet feature (their folds place moved faces).
+    pub sheets: Vec<crate::sheet::SheetBody>,
 }
 
 /// The lazily computed names of a body, shared by its clones.
@@ -334,6 +336,24 @@ fn geometric_from(b: &ModelBody, o: &NamingOrigin, nf: usize, names_of: fn(&Mode
             names = got.into_iter().map(|n| n.map(|n| format!("{n}@F{fid}.{}", k + 1))).collect();
         }
     }
+    // A sheet feature that moved panels (a fold, an unfold): faces it carried along lie on the
+    // faces they were, taken back through the panel they are on.
+    if let (Some(after), Some(before), Some(input)) = (
+        o.sheets.iter().find(|s| s.body == b.name),
+        o.before.sheets.iter().find(|s| s.body == b.name),
+        inputs.iter().find(|(x, _, _)| x.name == b.name),
+    ) {
+        let input = std::slice::from_ref(input);
+        for (name, ps) in names.iter_mut().zip(&pts) {
+            if name.is_some() {
+                continue;
+            }
+            let back: Option<Vec<Vec3>> = ps.iter().map(|p| after.point_before(before, *p)).collect();
+            if let Some(back) = back.filter(|b| !b.is_empty()) {
+                *name = vote(&back, input, tol, None);
+            }
+        }
+    }
     let empty = Vec::new();
     let names: Vec<String> = names
         .into_iter()

crates/doc/src/sheet.rs

@@ -1327,6 +1327,39 @@ impl SheetBody {
         v
     }
 
+    /// Where a world point of this sheet lay in `before`, the same sheet before a feature
+    /// changed its folds: the point goes back to flat coordinates through the panel it lies on
+    /// and is folded again the way `before` folded that material. A panel a fold made was part of
+    /// the panel it was folded out of. `None` off every panel (on a bend).
+    pub(crate) fn point_before(&self, before: &SheetBody, p: Vec3) -> Option<Vec3> {
+        const TOL: f64 = 1e-4;
+        for (pi, r) in self.panels() {
+            let Some(inv) = mat_inverse(&self.world(pi)) else { continue };
+            let q = apply_point(&inv, p);
+            if q.z < -TOL || q.z > self.t + TOL {
+                continue;
+            }
+            let q2 = Vec2::new(q.x, q.y);
+            let pts = dedup(&r.outer.ccw().polyline(1e-3));
+            if !point_in(&pts, q2) && !near_outline(&pts, q2, TOL) {
+                continue;
+            }
+            // Panels `before` did not have yet came out of their parent's (bounded walk).
+            let mut owner = pi;
+            for _ in 0..self.flanges.len() {
+                match owner {
+                    Some(i) if i >= before.flanges.len() => owner = self.flanges.get(i).and_then(|f| f.parent),
+                    _ => break,
+                }
+            }
+            if owner.is_some_and(|i| i >= before.flanges.len()) {
+                return None;
+            }
+            return Some(apply_point(&before.world(owner), q));
+        }
+        None
+    }
+
     /// The panel edge nearest a world point: (panel, edge a, edge b in flat coordinates, on the
     /// top face?, distance).
     pub fn edge_at(&self, p: Vec3) -> Option<(Option<usize>, Vec2, Vec2, bool, f64)> {
@@ -2409,6 +2442,19 @@ fn merge_loops(polys: &[Vec<Vec2>], work: &mut FlatWork) -> Result<Vec<Vec<Vec2>
     Ok(loops)
 }
 
+/// Whether `q` lies within `tol` of the closed polygon `poly`'s outline.
+fn near_outline(poly: &[Vec2], q: Vec2, tol: f64) -> bool {
+    let m = poly.len();
+    (0..m).any(|i| match (poly.get(i), poly.get((i + 1) % m)) {
+        (Some(&a), Some(&b)) => {
+            let d = b - a;
+            let t = if d.len2() > 1e-18 { ((q - a).dot(d) / d.len2()).clamp(0.0, 1.0) } else { 0.0 };
+            (a + d * t).dist(q) < tol
+        }
+        _ => false,
+    })
+}
+
 fn signed_area(p: &[Vec2]) -> f64 {
     let m = p.len();
     (0..m).filter_map(|i| Some(p.get(i)?.cross(*p.get((i + 1) % m)?))).sum::<f64>() / 2.0

crates/engine/src/cmd/sheet_tests.rs

@@ -2478,7 +2478,6 @@ fn hole_face_names(s: &mut Session) -> Vec<String> {
 }
 
 #[test]
-#[ignore = "fails until #535 is fixed"]
 fn a_hole_on_a_folded_panel_keeps_the_name_of_its_sketch_circle() {
     // A Ø10 hole at x = 20 on a 100 x 60 plate; the fold at x = 40 stands that (smaller) side up.
     let mut s = Session::default();