Mesh: Move hide flags to generic attributes

This commit moves the hide status of mesh vertices, edges, and faces
from the `ME_FLAG` to optional generic boolean attributes. Storing this
data as generic attributes can significantly simplify and improve code,
as described in T95965.

The attributes are called `.hide_vert`, `.hide_edge`, and `.hide_poly`,
using the attribute name semantics discussed in T97452. The `.` prefix
means they are "UI attributes", so they still contain original data
edited by users, but they aren't meant to be accessed procedurally by
the user in arbitrary situations. They are also be hidden in the
spreadsheet and the attribute list by default,

Until 4.0, the attributes are still written to and read from the mesh
in the old way, so neither forward nor backward compatibility are
affected. This means memory requirements will be increased by one byte
per element when the hide status is used. When the flags are removed
completely, requirements will decrease when hiding is unused.

Further notes:
 * Some code can be further simplified to skip some processing when the
   hide attributes don't exist.
 * The data is still stored in flags for `BMesh`, necessitating some
   complexity in the conversion to and from `Mesh`.
 * Access to the "hide" property of mesh elements in RNA is slower.
   The separate boolean arrays should be used where possible.

Ref T95965

Differential Revision: https://developer.blender.org/D14685

1 files changed, 24 insertions, 16 deletions

diff --git a/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_lines.cc b/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_lines.cc
index e6c0d815963..fe883fb0c96 100644
--- a/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_lines.cc
+++ b/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_lines.cc
@@ -58,14 +58,12 @@ static void extract_lines_iter_poly_mesh(const MeshRenderData *mr,
   GPUIndexBufBuilder *elb = static_cast<GPUIndexBufBuilder *>(data);
   /* Using poly & loop iterator would complicate accessing the adjacent loop. */
   const MLoop *mloop = mr->mloop;
-  const MEdge *medge = mr->medge;
   if (mr->use_hide || (mr->extract_type == MR_EXTRACT_MAPPED) || (mr->e_origindex != nullptr)) {
     const int ml_index_last = mp->loopstart + (mp->totloop - 1);
     int ml_index = ml_index_last, ml_index_next = mp->loopstart;
     do {
       const MLoop *ml = &mloop[ml_index];
-      const MEdge *med = &medge[ml->e];
-      if (!((mr->use_hide && (med->flag & ME_HIDE)) ||
+      if (!((mr->use_hide && mr->hide_edge && mr->hide_edge[ml->e]) ||
             ((mr->extract_type == MR_EXTRACT_MAPPED) && (mr->e_origindex) &&
              (mr->e_origindex[ml->e] == ORIGINDEX_NONE)))) {
         GPU_indexbuf_set_line_verts(elb, ml->e, ml_index, ml_index_next);
@@ -111,7 +109,7 @@ static void extract_lines_iter_ledge_mesh(const MeshRenderData *mr,
   GPUIndexBufBuilder *elb = static_cast<GPUIndexBufBuilder *>(data);
   const int l_index_offset = mr->edge_len + ledge_index;
   const int e_index = mr->ledges[ledge_index];
-  if (!((mr->use_hide && (med->flag & ME_HIDE)) ||
+  if (!((mr->use_hide && mr->hide_edge && mr->hide_edge[med - mr->medge]) ||
         ((mr->extract_type == MR_EXTRACT_MAPPED) && (mr->e_origindex) &&
          (mr->e_origindex[e_index] == ORIGINDEX_NONE)))) {
     const int l_index = mr->loop_len + ledge_index * 2;
@@ -185,9 +183,14 @@ static void extract_lines_loose_geom_subdiv(const DRWSubdivCache *subdiv_cache,
 
   switch (mr->extract_type) {
     case MR_EXTRACT_MESH: {
-      const MEdge *medge = mr->medge;
-      for (DRWSubdivLooseEdge edge : loose_edges) {
-        *flags_data++ = (medge[edge.coarse_edge_index].flag & ME_HIDE) != 0;
+      const bool *hide_vert = mr->hide_vert;
+      if (hide_vert) {
+        for (DRWSubdivLooseEdge edge : loose_edges) {
+          *flags_data++ = hide_vert[edge.coarse_edge_index];
+        }
+      }
+      else {
+        MutableSpan<uint>(flags_data, loose_edges.size()).fill(0);
       }
       break;
     }
@@ -199,18 +202,23 @@ static void extract_lines_loose_geom_subdiv(const DRWSubdivCache *subdiv_cache,
         }
       }
       else {
-        for (DRWSubdivLooseEdge edge : loose_edges) {
-          int e = edge.coarse_edge_index;
-
-          if (mr->e_origindex && mr->e_origindex[e] != ORIGINDEX_NONE) {
-            *flags_data++ = (mr->medge[mr->e_origindex[e]].flag & ME_HIDE) != 0;
-          }
-          else {
-            *flags_data++ = false;
+        const bool *hide_vert = mr->hide_vert;
+        if (hide_vert) {
+          for (DRWSubdivLooseEdge edge : loose_edges) {
+            int e = edge.coarse_edge_index;
+
+            if (mr->e_origindex && mr->e_origindex[e] != ORIGINDEX_NONE) {
+              *flags_data++ = hide_vert[edge.coarse_edge_index];
+            }
+            else {
+              *flags_data++ = false;
+            }
           }
         }
+        else {
+          MutableSpan<uint>(flags_data, loose_edges.size()).fill(0);
+        }
       }
-
       break;
     }
     case MR_EXTRACT_BMESH: {