1 files changed, 20 insertions, 8 deletions

diff --git a/source/blender/editors/mesh/editmesh_tools.c b/source/blender/editors/mesh/editmesh_tools.c
index 5dc4ffcad18..4de7143682a 100644
--- a/source/blender/editors/mesh/editmesh_tools.c
+++ b/source/blender/editors/mesh/editmesh_tools.c
@@ -2035,19 +2035,26 @@ static bool flip_custom_normals(BMesh *bm, BMLoopNorEditDataArray *lnors_ed_arr)
   }
 
   BMFace *f;
-  BMLoop *l;
-  BMIter iter_f, iter_l;
+  BMLoop *l, *l_start;
+  BMIter iter_f;
   BM_ITER_MESH (f, &iter_f, bm, BM_FACES_OF_MESH) {
+    /* Flip all the custom loop normals on the selected faces. */
     if (!BM_elem_flag_test(f, BM_ELEM_SELECT)) {
       continue;
     }
-    /* Flip all the custom loop normals on the selected faces. */
 
-    BM_ITER_ELEM (l, &iter_l, f, BM_LOOPS_OF_FACE) {
+    /* Because the winding has changed, we need to go the reverse way around the face to get the
+     * correct placement of the normals. However we need to derive the old loop index to get the
+     * correct data. Note that the first loop index is the same though. So the loop starts and ends
+     * in the same place as before the flip.
+     */
 
+    l_start = l = BM_FACE_FIRST_LOOP(f);
+    int old_index = BM_elem_index_get(l);
+    do {
       int loop_index = BM_elem_index_get(l);
 
-      BMLoopNorEditData *lnor_ed = lnors_ed_arr->lidx_to_lnor_editdata[loop_index];
+      BMLoopNorEditData *lnor_ed = lnors_ed_arr->lidx_to_lnor_editdata[old_index];
       BMLoopNorEditData *lnor_ed_new = lnors_ed_arr_new_full->lidx_to_lnor_editdata[loop_index];
       BLI_assert(lnor_ed != NULL && lnor_ed_new != NULL);
 
@@ -2055,7 +2062,10 @@ static bool flip_custom_normals(BMesh *bm, BMLoopNorEditDataArray *lnors_ed_arr)
 
       BKE_lnor_space_custom_normal_to_data(
           bm->lnor_spacearr->lspacearr[loop_index], lnor_ed->nloc, lnor_ed_new->clnors_data);
-    }
+
+      old_index++;
+      l = l->prev;
+    } while (l != l_start);
   }
   BM_loop_normal_editdata_array_free(lnors_ed_arr_new_full);
   return true;
@@ -4172,7 +4182,8 @@ static Base *mesh_separate_tagged(
   BKE_object_material_array_assign(bmain,
                                    base_new->object,
                                    BKE_object_material_array_p(obedit),
-                                   *BKE_object_material_len_p(obedit));
+                                   *BKE_object_material_len_p(obedit),
+                                   false);
 
   ED_object_base_select(base_new, BA_SELECT);
 
@@ -4244,7 +4255,8 @@ static Base *mesh_separate_arrays(Main *bmain,
   BKE_object_material_array_assign(bmain,
                                    base_new->object,
                                    BKE_object_material_array_p(obedit),
-                                   *BKE_object_material_len_p(obedit));
+                                   *BKE_object_material_len_p(obedit),
+                                   false);
 
   ED_object_base_select(base_new, BA_SELECT);