From 6e3b483c6d5b8aee67a5feb7aa9c94d4e0ca21ee Mon Sep 17 00:00:00 2001
From: Philipp Oeser <philipp@blender.org>
Date: Mon, 2 Jun 2025 16:15:21 +0200
Subject: [PATCH] Fix #139675: Mesh analysis crashes in editmode with instances

Caused by a67b5f6f6364146d824e9930d8c11130e11dc9bc

Since we dont necessarily act with `MeshExtractType::BMesh` (can be
`MeshExtractType::Mesh` as well -- and seems the specific mesh analysis
`statvis_calc` functions are well prepared for this), move access to
`BMesh` to the codepaths specific to `MeshExtractType::BMesh`.

Also remove (non-appropriate) assert in `extract_mesh_analysis`.

Pull Request: https://projects.blender.org/blender/blender/pulls/139717
---
 .../extract_mesh_vbo_mesh_analysis.cc         | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_mesh_analysis.cc b/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_mesh_analysis.cc
index b39e4d3906f..79948367f4b 100644
--- a/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_mesh_analysis.cc
+++ b/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_mesh_analysis.cc
@@ -61,10 +61,6 @@ static void statvis_calc_overhang(const MeshRenderData &mr,
   const float min = statvis->overhang_min / float(M_PI);
   const float max = statvis->overhang_max / float(M_PI);
   const char axis = statvis->overhang_axis;
-  BMEditMesh *em = mr.edit_bmesh;
-  BMIter iter;
-  BMesh *bm = em->bm;
-  BMFace *f;
   float dir[3];
   const float minmax_irange = 1.0f / (max - min);
 
@@ -77,6 +73,10 @@ static void statvis_calc_overhang(const MeshRenderData &mr,
   normalize_v3(dir);
 
   if (mr.extract_type == MeshExtractType::BMesh) {
+    BMEditMesh *em = mr.edit_bmesh;
+    BMIter iter;
+    BMesh *bm = em->bm;
+    BMFace *f;
     int l_index = 0;
     BM_ITER_MESH (f, &iter, bm, BM_FACES_OF_MESH) {
       float fac = angle_normalized_v3v3(bm_face_no_get(mr, f), dir) / float(M_PI);
@@ -133,7 +133,6 @@ static void statvis_calc_thickness(const MeshRenderData &mr,
   const float eps_offset = 0.00002f; /* values <= 0.00001 give errors */
   /* cheating to avoid another allocation */
   float *face_dists = r_thickness.data() + (mr.corners_num - mr.faces_num);
-  BMEditMesh *em = mr.edit_bmesh;
   const float scale = 1.0f / mat4_to_scale(object_to_world.ptr());
   const MeshStatVis *statvis = &mr.toolsettings->statvis;
   const float min = statvis->thickness_min * scale;
@@ -152,6 +151,7 @@ static void statvis_calc_thickness(const MeshRenderData &mr,
   }
 
   if (mr.extract_type == MeshExtractType::BMesh) {
+    BMEditMesh *em = mr.edit_bmesh;
     BMesh *bm = em->bm;
     BM_mesh_elem_index_ensure(bm, BM_FACE);
 
@@ -293,13 +293,12 @@ static bool bvh_overlap_cb(void *userdata, int index_a, int index_b, int /*threa
 
 static void statvis_calc_intersect(const MeshRenderData &mr, MutableSpan<float> r_intersect)
 {
-  BMEditMesh *em = mr.edit_bmesh;
-
   for (int l_index = 0; l_index < mr.corners_num; l_index++) {
     r_intersect[l_index] = -1.0f;
   }
 
   if (mr.extract_type == MeshExtractType::BMesh) {
+    BMEditMesh *em = mr.edit_bmesh;
     uint overlap_len;
     BMesh *bm = em->bm;
 
@@ -376,13 +375,13 @@ BLI_INLINE float distort_remap(float fac, float min, float /*max*/, float minmax
 
 static void statvis_calc_distort(const MeshRenderData &mr, MutableSpan<float> r_distort)
 {
-  BMEditMesh *em = mr.edit_bmesh;
   const MeshStatVis *statvis = &mr.toolsettings->statvis;
   const float min = statvis->distort_min;
   const float max = statvis->distort_max;
   const float minmax_irange = 1.0f / (max - min);
 
   if (mr.extract_type == MeshExtractType::BMesh) {
+    BMEditMesh *em = mr.edit_bmesh;
     BMIter iter;
     BMesh *bm = em->bm;
     BMFace *f;
@@ -479,7 +478,6 @@ BLI_INLINE float sharp_remap(float fac, float min, float /*max*/, float minmax_i
 
 static void statvis_calc_sharp(const MeshRenderData &mr, MutableSpan<float> r_sharp)
 {
-  BMEditMesh *em = mr.edit_bmesh;
   const MeshStatVis *statvis = &mr.toolsettings->statvis;
   const float min = statvis->sharp_min;
   const float max = statvis->sharp_max;
@@ -490,6 +488,7 @@ static void statvis_calc_sharp(const MeshRenderData &mr, MutableSpan<float> r_sh
   copy_vn_fl(vert_angles, mr.verts_num, -M_PI);
 
   if (mr.extract_type == MeshExtractType::BMesh) {
+    BMEditMesh *em = mr.edit_bmesh;
     BMIter iter;
     BMesh *bm = em->bm;
     BMFace *efa;
@@ -573,8 +572,6 @@ static void statvis_calc_sharp(const MeshRenderData &mr, MutableSpan<float> r_sh
 
 gpu::VertBufPtr extract_mesh_analysis(const MeshRenderData &mr, const float4x4 &object_to_world)
 {
-  BLI_assert(mr.edit_bmesh);
-
   static const GPUVertFormat format = GPU_vertformat_from_attribute(
       "weight", GPU_COMP_F32, 1, GPU_FETCH_FLOAT);