From 1a7757b0bc6945ab7d3b281f3e0dd7130bcf80f0 Mon Sep 17 00:00:00 2001 From: Campbell Barton Date: Fri, 12 Nov 2021 18:07:07 +1100 Subject: [PATCH] Fix T91444: Edge Loop Preview fails with two Mirror Modifiers The mirror modifiers merge option caused unnecessary re-ordering to the vertex array with original vertices merging into their copies. While this wasn't an error, it meant creating a 1:1 mapping from input vertices to their final output wasn't reliable (when looping over vertices first to last) as is done in BKE_editmesh_vert_coords_when_deformed. As merging in either direction is supported, keep the source meshes vertices in-order since it allows the vertex coordinates to be extracted. --- source/blender/blenkernel/intern/mesh_mirror.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/source/blender/blenkernel/intern/mesh_mirror.c b/source/blender/blenkernel/intern/mesh_mirror.c index b20d81e7b9c..6df13e71e72 100644 --- a/source/blender/blenkernel/intern/mesh_mirror.c +++ b/source/blender/blenkernel/intern/mesh_mirror.c @@ -260,10 +260,16 @@ Mesh *BKE_mesh_mirror_apply_mirror_on_axis_for_modifier(MirrorModifierData *mmd, mul_m4_v3(mtx, mv->co); if (do_vtargetmap) { - /* compare location of the original and mirrored vertex, to see if they - * should be mapped for merging */ + /* Compare location of the original and mirrored vertex, + * to see if they should be mapped for merging. + * + * Always merge from the copied into the original vertices so it's possible to + * generate a 1:1 mapping by scanning vertices from the beginning of the array + * as is done in #BKE_editmesh_vert_coords_when_deformed. Without this, + * the coordinates returned will sometimes point to the copied vertex locations, see: T91444. + */ if (UNLIKELY(len_squared_v3v3(mv_prev->co, mv->co) < tolerance_sq)) { - *vtmap_a = maxVerts + i; + *vtmap_b = i; tot_vtargetmap++; /* average location */ @@ -271,10 +277,11 @@ Mesh *BKE_mesh_mirror_apply_mirror_on_axis_for_modifier(MirrorModifierData *mmd, copy_v3_v3(mv_prev->co, mv->co); } else { - *vtmap_a = -1; + *vtmap_b = -1; } - *vtmap_b = -1; /* fill here to avoid 2x loops */ + /* Fill here to avoid 2x loops. */ + *vtmap_a = -1; vtmap_a++; vtmap_b++;