fix [#36363] ray_cast face index with n_gons

1 files changed, 17 insertions, 2 deletions

diff --git a/source/blender/makesrna/intern/rna_object_api.c b/source/blender/makesrna/intern/rna_object_api.c
index a4e532660f1..25ca231e58d 100644
--- a/source/blender/makesrna/intern/rna_object_api.c
+++ b/source/blender/makesrna/intern/rna_object_api.c
@@ -259,6 +259,21 @@ static void rna_Mesh_assign_verts_to_group(Object *ob, bDeformGroup *group, int
 }
 #endif
 
+/* don't call inside a loop */
+static int dm_tessface_to_poly_index(DerivedMesh *dm, int tessface_index)
+{
+	if (tessface_index != ORIGINDEX_NONE) {
+		/* double lookup */
+		const int *index_mf_to_mpoly;
+		if ((index_mf_to_mpoly = dm->getTessFaceDataArray(dm, CD_ORIGINDEX))) {
+			const int *index_mp_to_orig = dm->getPolyDataArray(dm, CD_ORIGINDEX);
+			return DM_origindex_mface_mpoly(index_mf_to_mpoly, index_mp_to_orig, tessface_index);
+		}
+	}
+
+	return ORIGINDEX_NONE;
+}
+
 /* BMESH_TODO, return polygon index, not tessface */
 static void rna_Object_ray_cast(Object *ob, ReportList *reports, float ray_start[3], float ray_end[3],
                                 float r_location[3], float r_normal[3], int *index)
@@ -291,7 +306,7 @@ static void rna_Object_ray_cast(Object *ob, ReportList *reports, float ray_start
 			if (hit.dist <= dist) {
 				copy_v3_v3(r_location, hit.co);
 				copy_v3_v3(r_normal, hit.no);
-				*index = hit.index;
+				*index = dm_tessface_to_poly_index(ob->derivedFinal, hit.index);
 				return;
 			}
 		}
@@ -330,7 +345,7 @@ static void rna_Object_closest_point_on_mesh(Object *ob, ReportList *reports, fl
 		if (BLI_bvhtree_find_nearest(treeData.tree, point_co, &nearest, treeData.nearest_callback, &treeData) != -1) {
 			copy_v3_v3(n_location, nearest.co);
 			copy_v3_v3(n_normal, nearest.no);
-			*index = nearest.index;
+			*index = dm_tessface_to_poly_index(ob->derivedFinal, nearest.index);
 			return;
 		}
 	}