Measuring bodies of thousands of faces: 13 s to 0.8 s for 5000 faces (the body's size was recomputed for every face); merged topology counts right on finely faceted bodies (vertices welded only when they coincide, planes merged only when parallel within 1e-9), with a test

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/kernel/src/tests.rs

@@ -1360,3 +1360,22 @@ fn boolean_of_a_body_in_pieces() {
     let v = measure(&cut).unwrap().volume;
     assert!((v - (2000.0 - 2.0 * PI * 4.0 * 10.0)).abs() < 1.0, "{v}");
 }
+
+/// Measuring a body of 5000 faces (a modelled thread is like that) stays fast and counts
+/// right: 0.8 s here, it took 13 s (a per-face recomputation of the body's size).
+#[test]
+fn measure_of_a_body_with_many_faces() {
+    let n = 5000;
+    let pts: Vec<Vec2> = (0..n)
+        .map(|i| {
+            let a = std::f64::consts::TAU * i as f64 / n as f64;
+            Vec2::new(20.0 * a.cos(), 20.0 * a.sin())
+        })
+        .collect();
+    let b = extrude(&Plane::XY, &[Region2 { outer: Loop2::polygon(&pts), holes: vec![] }], 0.0, 10.0).unwrap().pop().unwrap();
+    let t = std::time::Instant::now();
+    let m = measure(&b).unwrap();
+    // (A loaded build machine runs slower; the bound is loose.)
+    assert!(t.elapsed().as_secs_f64() < 5.0, "{:?}", t.elapsed());
+    assert_eq!((m.merged.faces, m.merged.edges, m.merged.vertices), (n + 2, 3 * n, 2 * n), "{:?}", m.merged);
+}

crates/kernel/src/topo.rs

@@ -42,7 +42,7 @@ impl Surf {
     }
     fn same(&self, o: &Surf, tol: f64) -> bool {
         match (*self, *o) {
-            (Surf::Plane { n, d }, Surf::Plane { n: n2, d: d2 }) => n.dot(n2) > 1.0 - 1e-6 && (d - d2).abs() < tol,
+            (Surf::Plane { n, d }, Surf::Plane { n: n2, d: d2 }) => n.dot(n2) > 1.0 - 1e-9 && (d - d2).abs() < tol,
             (Surf::Cylinder { axis, p, r }, Surf::Cylinder { axis: a2, p: p2, r: r2 }) => {
                 let off = p2 - p;
                 axis.dot(a2).abs() > 1.0 - 1e-6 && (r - r2).abs() < tol && (off - axis * off.dot(axis)).len() < tol
@@ -382,13 +382,14 @@ pub fn merged_topology(b: &Body, mesh: &Mesh) -> Result<TopoCounts> {
             *a += (q - p).cross(r - p).len() * 0.5;
         }
     }
-    let degenerate: Vec<bool> = area.iter().map(|a| *a < (b.size() * 1e-6).powi(2)).collect();
+    let tiny = (b.size() * 1e-6).powi(2);
+    let degenerate: Vec<bool> = area.iter().map(|a| *a < tiny).collect();
     let is_deg = |f: usize| degenerate.get(f).copied().unwrap_or(false);
 
     // Edge → faces, edge → vertices. Vertices and edges lying on each other count once (two
     // tangent holes touch along a line that both bodies' pieces carry): welded by position,
     // edges by their ends and the point halfway along them.
-    let q = tol * 10.0;
+    let q = (b.size() * 1e-6).max(1e-9);
     let cell = |p: Vec3| ((p.x / q).round() as i64, (p.y / q).round() as i64, (p.z / q).round() as i64);
     let mut edge_faces: HashMap<usize, Vec<usize>> = HashMap::new();
     let mut edge_verts: HashMap<usize, (usize, usize)> = HashMap::new();
@@ -528,7 +529,7 @@ pub fn merged_topology(b: &Body, mesh: &Mesh) -> Result<TopoCounts> {
         }
     }
     let mut ep: Vec<usize> = (0..remaining.len()).collect();
-    let mut merge_vertex: Vec<usize> = Vec::new();
+    let mut merge_vertex: std::collections::HashSet<usize> = std::collections::HashSet::new();
     for (v, es) in &deg {
         if let [i, j] = es[..]
             && let (Some(a), Some(b)) = (remaining.get(i), remaining.get(j))
@@ -538,7 +539,7 @@ pub fn merged_topology(b: &Body, mesh: &Mesh) -> Result<TopoCounts> {
             if let Some(s) = ep.get_mut(ri) {
                 *s = rj;
             }
-            merge_vertex.push(*v);
+            merge_vertex.insert(*v);
         }
     }
     let mut edge_groups: BTreeMap<usize, bool> = BTreeMap::new(); // root → has a real end vertex