fix: reject degenerate boolean intersection polylines

ATTRIBUTION.md

@@ -55,7 +55,7 @@ Generated-in-code assets are original and have no file to list:
 |---|---|---|---|
 | vendor/truck-meshalgo | truck-meshalgo 0.4.0, https://github.com/ricosjp/truck (RICOS Co. Ltd.) | Apache-2.0 | meshing: parameter searches kept inside the surface domain (vendor/README.md) |
 | vendor/truck-stepio | truck-stepio 0.3.0, https://github.com/ricosjp/truck (RICOS Co. Ltd.) | Apache-2.0 | STEP writer: intersection-curve surfaces written at unique ids (vendor/README.md) |
-| vendor/truck-shapeops | truck-shapeops 0.4.0, https://github.com/ricosjp/truck (RICOS Co. Ltd.) | Apache-2.0 | robust meshing and nearest-parameter fallback in booleans; trace macro (vendor/README.md) |
+| vendor/truck-shapeops | truck-shapeops 0.4.0, https://github.com/ricosjp/truck (RICOS Co. Ltd.) | Apache-2.0 | robust meshing and nearest-parameter fallback in booleans; degenerate intersection-curve rejection; trace macro (vendor/README.md) |
 | vendor/matext4cgmath | matext4cgmath 0.1.0, https://github.com/ricosjp/matext4cgmath (RICOS Co. Ltd.) | Apache-2.0 | root refinement stops after 100 Newton steps (vendor/README.md) |
 
 ## Vendored renderer compatibility fix

ROADMAP.md

@@ -304,6 +304,9 @@ headline counts in-scope tabs only and lists the deferred ones separately.
 
 ## Kernel
 
+- Boolean intersection-curve construction refuses point-only, collapsed and non-finite
+  polylines without panicking. Direct constructor regressions retain valid open endpoints
+  and closed spherical intersections; the original interactive trigger remains unidentified.
 - Shell of a stepped, joined planar body no longer creates horizontal subdivisions across
   continuous walls. Fresh axis-aligned Cut walls are stitched using their exact construction
   support and shared topology, preserving real steps and intentional boundaries. The local

crates/kernel/src/intersection_curve_tests.rs

@@ -0,0 +1,60 @@
+//! Regressions against the actual patched truck constructor, run by workspace CI.
+use truck_meshalgo::prelude::PolylineCurve;
+use truck_modeling::{BoundedCurve, ParametricCurve, Plane, Point3, Sphere};
+use truck_shapeops::IntersectionCurveWithParameters;
+
+fn planes() -> (Plane, Plane) {
+    let o = Point3::new(0.0, 0.0, 0.0);
+    (Plane::new(o, Point3::new(1.0, 0.0, 0.0), Point3::new(0.0, 1.0, 0.0)), Plane::new(o, Point3::new(1.0, 0.0, 0.0), Point3::new(0.0, 0.0, 1.0)))
+}
+
+#[test]
+fn degenerate_intersection_polylines_return_none_without_panicking() {
+    let origin = Point3::new(0.0, 0.0, 0.0);
+    for points in [
+        vec![],
+        vec![origin],
+        vec![origin, origin],
+        vec![origin; 3],
+        vec![origin, Point3::new(f64::NAN, 0.0, 0.0)],
+        vec![origin, Point3::new(f64::INFINITY, 0.0, 0.0)],
+    ] {
+        let (a, b) = planes();
+        let result = std::panic::catch_unwind(|| IntersectionCurveWithParameters::try_new(a, b, PolylineCurve(points.clone()), 0.01));
+        assert!(result.is_ok(), "constructor panicked for {points:?}");
+        assert!(result.unwrap().is_none(), "collapsed input must not create a curve: {points:?}");
+    }
+}
+
+#[test]
+fn closed_intersection_retains_the_closure_and_spherical_supports() {
+    let a = Sphere::new(Point3::new(0.0, 0.0, 1.0), 2.0_f64.sqrt());
+    let b = Sphere::new(Point3::new(0.0, 0.0, -1.0), 2.0_f64.sqrt());
+    let poly = PolylineCurve(vec![
+        Point3::new(1.0, 0.0, 0.0),
+        Point3::new(0.0, 1.0, 0.0),
+        Point3::new(-1.0, 0.0, 0.0),
+        Point3::new(0.0, -1.0, 0.0),
+        Point3::new(1.0, 0.0, 0.0),
+    ]);
+    let curve = IntersectionCurveWithParameters::try_new(a, b, poly, 0.01).unwrap();
+    let (lo, hi) = curve.range_tuple();
+    assert_eq!(curve.subs(lo), curve.subs(hi));
+    for i in 0..=40 {
+        let p = curve.subs(lo + (hi - lo) * i as f64 / 40.0);
+        assert!(p.z.abs() < 1e-8, "{p:?}");
+        assert!(((p.x * p.x + p.y * p.y).sqrt() - 1.0).abs() <= 0.01, "{p:?}");
+    }
+}
+
+#[test]
+fn open_intersection_keeps_endpoints_on_both_planes() {
+    let (a, b) = planes();
+    let start = Point3::new(1.0, 0.0, 0.0);
+    let end = Point3::new(3.0, 0.0, 0.0);
+    let curve = IntersectionCurveWithParameters::try_new(a, b, PolylineCurve(vec![start, end]), 0.01).unwrap();
+    let (lo, hi) = curve.range_tuple();
+    assert_eq!(curve.subs(lo), start);
+    assert_eq!(curve.subs(hi), end);
+    assert_eq!(curve.subs((lo + hi) / 2.0), Point3::new(2.0, 0.0, 0.0));
+}

crates/kernel/src/lib.rs

@@ -30,6 +30,8 @@ mod heal;
 mod helix;
 mod iges_in;
 mod iges_out;
+#[cfg(test)]
+mod intersection_curve_tests;
 mod lip;
 mod loopblend;
 mod measure;

vendor/README.md

@@ -7,6 +7,9 @@ are marked `SolveCraft:` in the source.
 ## truck-shapeops 0.4.0 (Apache-2.0, © RICOS Co. Ltd., https://github.com/ricosjp/truck)
 
 Changes:
+- `transversal/intersection_curve/mod.rs`: reject empty/single-point polylines and
+  collapsed or non-finite segments before endpoint indexing and normalization. A hidden
+  constructor re-export lets the kernel workspace tests exercise the actual vendored code.
 - `transversal/integrate/mod.rs`: mesh both shells with `robust_triangulation` (faces made by
   earlier booleans have boundaries that lie on their surface only within tolerance).
 - `transversal/divide_face/mod.rs`: when projecting a loop onto a face's surface, fall back to

vendor/truck-shapeops/src/lib.rs

@@ -34,4 +34,7 @@ mod healing;
 pub use healing::{RobustSplitClosedEdgesAndFaces, SplitClosedEdgesAndFaces};
 mod transversal;
 pub use transversal::{and, or, ShapeOpsCurve, ShapeOpsSurface};
+// SolveCraft: exercised by kernel regressions in the workspace CI.
+#[doc(hidden)]
+pub use transversal::IntersectionCurveWithParameters;
 mod alternative;

vendor/truck-shapeops/src/transversal/intersection_curve/mod.rs

@@ -19,12 +19,21 @@ impl<S> From<IntersectionCurveWithParameters<S>> for IntersectionCurve<PolylineC
 impl<S> IntersectionCurveWithParameters<S>
 where S: ParametricSurface3D + SearchNearestParameter<D2, Point = Point3>
 {
+    /// SolveCraft: construct a projected curve, returning `None` for degenerate input.
     pub fn try_new(
         surface0: S,
         surface1: S,
         poly: PolylineCurve<Point3>,
         tol: f64,
     ) -> Option<Self> {
+        // SolveCraft: a point contact is not a curve. Reject it before indexing the
+        // endpoints, and reject collapsed/non-finite segments before normalizing.
+        if poly.len() < 2 || poly.windows(2).any(|p| {
+            let length2 = (p[1] - p[0]).magnitude2();
+            !length2.is_finite() || length2 <= 0.0
+        }) {
+            return None;
+        }
         let mut polyline = PolylineCurve(Vec::new());
         let mut params0 = PolylineCurve(Vec::new());
         let mut params1 = PolylineCurve(Vec::new());

vendor/truck-shapeops/src/transversal/mod.rs

@@ -2,6 +2,9 @@ mod divide_face;
 mod faces_classification;
 mod integrate;
 mod intersection_curve;
+// SolveCraft: expose the constructor for workspace regression coverage of the vendored fix.
+#[doc(hidden)]
+pub use intersection_curve::IntersectionCurveWithParameters;
 mod loops_store;
 mod polyline_construction;
 pub use integrate::{and, or, ShapeOpsCurve, ShapeOpsSurface};