From bf7cdc522987b5c8675ccaafdb4b2c5d2b19e726 Mon Sep 17 00:00:00 2001
From: Malcolm Nixon <Malcolm.nixon@gmail.com>
Date: Fri, 1 Dec 2023 16:38:08 -0500
Subject: [PATCH] Fix memory corruption and assert failures in convex
 decomposition

This PR fixes how triangular faces are decomposed into vertices and indices. The pre-increment resulted in the indices table skipping entry 0 and potentially overrunning the end of the vertices vector.
---
 scene/resources/importer_mesh.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scene/resources/importer_mesh.cpp b/scene/resources/importer_mesh.cpp
index 1f4171c07203..66d758080e1a 100644
--- a/scene/resources/importer_mesh.cpp
+++ b/scene/resources/importer_mesh.cpp
@@ -969,7 +969,7 @@ Vector<Ref<Shape3D>> ImporterMesh::convex_decompose(const Ref<MeshConvexDecompos
 				if (found_vertex) {
 					index = found_vertex->value;
 				} else {
-					index = ++vertex_count;
+					index = vertex_count++;
 					vertex_map[vertex] = index;
 					vertex_w[index] = vertex;
 				}