From 124317ea66184aa65d4c66273045df53702fb61d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Crozet?= <sebcrozet@dimforge.com>
Date: Mon, 6 Jan 2025 19:01:09 +0100
Subject: [PATCH] fix: always compute mesh connected-components from union-find

---
 CHANGELOG.md         |  7 ++++++
 src/shape/trimesh.rs | 51 --------------------------------------------
 2 files changed, 7 insertions(+), 51 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2a384b27..c09b3e7d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,13 @@
 - Removed `IntersectionCompositeShapeShapeBestFirstVisitor` (which had been deprecated for a while):
   use `IntersectionCompositeShapeShapeVisitor` instead.
 
+## v0.17.5
+
+### Fix
+
+- Always compute connected-components from union-find instead of topology. It is faster and the function based on
+  topology could result in a crash for non-manifold meshes.
+
 ## v0.17.4
 
 ### Added
diff --git a/src/shape/trimesh.rs b/src/shape/trimesh.rs
index ac38dc0a..79ff9237 100644
--- a/src/shape/trimesh.rs
+++ b/src/shape/trimesh.rs
@@ -806,14 +806,6 @@ impl TriMesh {
     // NOTE: this is private because that calculation is controlled by TriMeshFlags::CONNECTED_COMPONENTS
     // TODO: we should remove the CONNECTED_COMPONENTS flags and just have this be a free function.
     fn compute_connected_components(&mut self) {
-        if self.topology.is_some() {
-            self.compute_connected_components_from_topology()
-        } else {
-            self.compute_connected_components_union_find()
-        }
-    }
-
-    fn compute_connected_components_union_find(&mut self) {
         use ena::unify::{InPlaceUnificationTable, UnifyKey};
 
         #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
@@ -903,49 +895,6 @@ impl TriMesh {
         })
     }
 
-    fn compute_connected_components_from_topology(&mut self) {
-        let topo = self.topology.as_ref().unwrap();
-        let mut face_colors = vec![u32::MAX; topo.faces.len()];
-        let mut grouped_faces = Vec::new();
-        let mut ranges = vec![0];
-        let mut stack = vec![];
-
-        for i in 0..topo.faces.len() {
-            if face_colors[i] == u32::MAX {
-                let color = ranges.len() as u32 - 1;
-                face_colors[i] = color;
-                grouped_faces.push(i as u32);
-                stack.push(i as u32);
-
-                while let Some(tri_id) = stack.pop() {
-                    let eid = topo.faces[tri_id as usize].half_edge;
-                    let edge_a = &topo.half_edges[eid as usize];
-                    let edge_b = &topo.half_edges[edge_a.next as usize];
-                    let edge_c = &topo.half_edges[edge_b.next as usize];
-                    let edges = [edge_a, edge_b, edge_c];
-
-                    for edge in edges {
-                        if let Some(twin) = topo.half_edges.get(edge.twin as usize) {
-                            if face_colors[twin.face as usize] == u32::MAX {
-                                face_colors[twin.face as usize] = color;
-                                grouped_faces.push(twin.face);
-                                stack.push(twin.face);
-                            }
-                        }
-                    }
-                }
-
-                ranges.push(grouped_faces.len());
-            }
-        }
-
-        self.connected_components = Some(TriMeshConnectedComponents {
-            face_colors,
-            grouped_faces,
-            ranges,
-        });
-    }
-
     #[allow(dead_code)] // Useful for testing.
     pub(crate) fn assert_half_edge_topology_is_valid(&self) {
         let topo = self