A round hole elsewhere on a body no longer breaks a loft cut beside it: a loft cut from a pocket floor (556.68 x 99 down 4 mm to 80 x 80), with a 35 mm hole 66 mm away that it never touches, failed with a kernel panic in TroughFall, while the same cut without the hole, or with the hole made afterwards, worked

The loft's top lies in the pocket floor. truck's boolean cannot take coincident faces, and the exact polygon fallback (planar_boolean) only takes bodies whose faces are all planar, so the hole's cylinder ruled out the only path that handles this cut. planar_boolean now first tries a sliced form: when an axis-aligned slab holds the tool and none of the body's curved faces, the body is split on the slab's planes (planes clear of the body's own faces), the planar middle piece takes the exact boolean, and the pieces outside are glued back on along the cut faces (the middle piece is healed first so its edges match theirs). Pieces in several parts are refused rather than glued into one shell. split_by_plane's half-space code is now ops::half_space, which this uses.

Tests: loft_cut_beside_a_round_hole replays examples/regressions/loft_cut_beside_round_hole.json and checks the exact volume (slab - pocket - prismatoid - hole; fails on main). With the hole made after the loft, the body is the same (volume, area, 19 faces, 42 edges).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/kernel/src/ops.rs

@@ -515,6 +515,15 @@ pub fn transform(body: &Body, translate: Vec3, origin: Vec3, axis: Vec3, angle:
 /// Split a body with a plane: the parts on the positive and the negative side of the plane
 /// (only the non-empty ones).
 pub fn split_by_plane(body: &Body, plane: &solvecraft_geom::Plane) -> Result<Vec<Body>> {
+    let mut out = Vec::new();
+    for positive in [true, false] {
+        out.extend(half_space(body, plane, positive)?);
+    }
+    Ok(out)
+}
+
+/// The part of a body on one side of a plane (`None` when nothing is there).
+pub(crate) fn half_space(body: &Body, plane: &solvecraft_geom::Plane, positive: bool) -> Result<Option<Body>> {
     body.require_brep("split")?;
     let size = body.size();
     let mut bb = solvecraft_geom::Aabb3::EMPTY;
@@ -532,12 +541,7 @@ pub fn split_by_plane(body: &Body, plane: &solvecraft_geom::Plane) -> Result<Vec
         ]),
         holes: vec![],
     };
-    let mut out = Vec::new();
-    for (lo, hi) in [(0.0, reach), (-reach, 0.0)] {
-        let half = crate::build::extrude(plane, std::slice::from_ref(&sq), lo, hi)?.pop().ok_or_else(|| KernelError::Failed("half space".into()))?;
-        if let Some(part) = boolean(body, &half, BoolOp::Intersect)? {
-            out.push(part);
-        }
-    }
-    Ok(out)
+    let (lo, hi) = if positive { (0.0, reach) } else { (-reach, 0.0) };
+    let half = crate::build::extrude(plane, std::slice::from_ref(&sq), lo, hi)?.pop().ok_or_else(|| KernelError::Failed("half space".into()))?;
+    boolean(body, &half, BoolOp::Intersect)
 }