Add surface indices to TriangleMesh

Helps unblock #56597

1 files changed, 11 insertions, 0 deletions

diff --git a/scene/resources/mesh.cpp b/scene/resources/mesh.cpp
index b8c83ac89e..3e7b0a2808 100644
--- a/scene/resources/mesh.cpp
+++ b/scene/resources/mesh.cpp
@@ -188,7 +188,10 @@ Ref<TriangleMesh> Mesh::generate_triangle_mesh() const {
 
 	Vector<Vector3> faces;
 	faces.resize(faces_size);
+	Vector<int32_t> surface_indices;
+	surface_indices.resize(faces_size / 3);
 	Vector3 *facesw = faces.ptrw();
+	int32_t *surface_indicesw = surface_indices.ptrw();
 
 	int widx = 0;
 
@@ -210,6 +213,8 @@ Ref<TriangleMesh> Mesh::generate_triangle_mesh() const {
 		Vector<Vector3> vertices = a[ARRAY_VERTEX];
 		const Vector3 *vr = vertices.ptr();
 
+		int32_t from_index = widx / 3;
+
 		if (surface_get_format(i) & ARRAY_FORMAT_INDEX) {
 			int ic = surface_get_array_index_len(i);
 			Vector<int> indices = a[ARRAY_INDEX];
@@ -241,6 +246,12 @@ Ref<TriangleMesh> Mesh::generate_triangle_mesh() const {
 				}
 			}
 		}
+
+		int32_t to_index = widx / 3;
+
+		for (int j = from_index; j < to_index; j++) {
+			surface_indicesw[j] = i;
+		}
 	}
 
 	triangle_mesh = Ref<TriangleMesh>(memnew(TriangleMesh));