Through-all holes beside walls: a long thin tool keeps its outside out (#629)

Body::new no longer turns a long thin solid (a through-all hole's tool) inside out on the strength of a coarse mesh volume: it checks again on a fine mesh first. 79 more face.hole actions pass in the action matrix; the remaining no-result cuts stay under #559.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/kernel/src/body.rs

@@ -477,13 +477,26 @@ impl Body {
             if lo.x.is_finite() { (hi - lo).len() } else { 1.0 }
         };
         let tol = (span * 0.01).clamp(1e-3, 1.0);
-        let (v, missing) = guard("orient", || {
-            let shells = mesh_shells(&solid, tol);
-            let volume = shells.iter().map(|s| s.to_polygon().volume()).sum::<f64>();
-            let missing =
-                shells.iter().flat_map(|s| s.face_iter()).filter(|f| f.surface().is_none_or(|m| m.faces().triangle_iter().next().is_none())).count();
-            Ok((volume, missing))
-        })?;
+        let orient = |tol: f64| {
+            guard("orient", || {
+                let shells = mesh_shells(&solid, tol);
+                let volume = shells.iter().map(|s| s.to_polygon().volume()).sum::<f64>();
+                let missing = shells
+                    .iter()
+                    .flat_map(|s| s.face_iter())
+                    .filter(|f| f.surface().is_none_or(|m| m.faces().triangle_iter().next().is_none()))
+                    .count();
+                Ok((volume, missing))
+            })
+        };
+        let (mut v, mut missing) = orient(tol)?;
+        // A long thin round part (a through hole's tool: a cylinder whose vertices all lie on
+        // its seam, so they span its length only) meshed that coarsely can come out with a
+        // negative volume when it is outward already: check finely before turning it inside out.
+        let fine = (tol * 0.02).max(1e-4);
+        if v < 0.0 && fine < tol {
+            (v, missing) = orient(fine)?;
+        }
         if v < 0.0 {
             solid.not();
         }

crates/kernel/src/body_lump_tests.rs

@@ -303,3 +303,19 @@ fn grouping_lumps_does_not_infer_absent_or_misaligned_sources() {
     let malformed = body.with_face_sources(Some(std::sync::Arc::new(vec![None])));
     assert!(malformed.lumps().unwrap_err().to_string().contains("face source table"));
 }
+
+/// A long thin cylinder (a through hole's tool) far from the origin, its seam turned: its
+/// vertices span only its length, so the coarse orientation mesh can give it a negative volume.
+/// It must still come out outward, or a Cut with it removes the wrong side (#559).
+#[test]
+fn a_long_thin_cylinder_comes_out_outward() {
+    use solidcraft_geom::{Loop2, Plane, Region2, Vec2, Vec3};
+    let plane = Plane::from_normal(Vec3::new(0., 24., 30.), Vec3::Z).unwrap();
+    for (lo, seam) in [(-181.0, 0.613), (-100.0, 0.613), (-10.0, 0.613), (-181.0, 0.0)] {
+        let disc = Region2 { outer: Loop2::circle_from(Vec2::ZERO, 0.5, seam), holes: vec![] };
+        let tool = crate::extrude(&plane, &[disc], lo, 0.9).unwrap().pop().unwrap();
+        let volume = tool.tessellate(0.01).unwrap().measure().volume;
+        let want = std::f64::consts::PI * 0.25 * (0.9 - lo);
+        assert!((volume - want).abs() < want * 0.02, "{lo} {seam}: {volume} vs {want}");
+    }
+}