Mesh: Remove redundant custom data pointers

For copy-on-write, we want to share attribute arrays between meshes
where possible. Mutable pointers like `Mesh.mvert` make that difficult
by making ownership vague. They also make code more complex by adding
redundancy.

The simplest solution is just removing them and retrieving layers from
`CustomData` as needed. Similar changes have already been applied to
curves and point clouds (e9f82d3dc7ee, 410a6efb747f). Removing use of
the pointers generally makes code more obvious and more reusable.

Mesh data is now accessed with a C++ API (`Mesh::edges()` or
`Mesh::edges_for_write()`), and a C API (`BKE_mesh_edges(mesh)`).

The CoW changes this commit makes possible are described in T95845
and T95842, and started in D14139 and D14140. The change also simplifies
the ongoing mesh struct-of-array refactors from T95965.

**RNA/Python Access Performance**
Theoretically, accessing mesh elements with the RNA API may become
slower, since the layer needs to be found on every random access.
However, overhead is already high enough that this doesn't make a
noticible differenc, and performance is actually improved in some
cases. Random access can be up to 10% faster, but other situations
might be a bit slower. Generally using `foreach_get/set` are the best
way to improve performance. See the differential revision for more
discussion about Python performance.

Cycles has been updated to use raw pointers and the internal Blender
mesh types, mostly because there is no sense in having this overhead
when it's already compiled with Blender. In my tests this roughly
halves the Cycles mesh creation time (0.19s to 0.10s for a 1 million
face grid).

Differential Revision: https://developer.blender.org/D15488

1 files changed, 28 insertions, 41 deletions

diff --git a/source/blender/blenkernel/intern/fluid.c b/source/blender/blenkernel/intern/fluid.c
index 74ff10cc32c..24c61a792eb 100644
--- a/source/blender/blenkernel/intern/fluid.c
+++ b/source/blender/blenkernel/intern/fluid.c
@@ -403,7 +403,8 @@ static void manta_set_domain_from_mesh(FluidDomainSettings *fds,
   size_t i;
   float min[3] = {FLT_MAX, FLT_MAX, FLT_MAX}, max[3] = {-FLT_MAX, -FLT_MAX, -FLT_MAX};
   float size[3];
-  MVert *verts = me->mvert;
+
+  MVert *verts = BKE_mesh_vertices_for_write(me);
   float scale = 0.0;
   int res;
 
@@ -994,9 +995,7 @@ static void obstacles_from_mesh(Object *coll_ob,
 {
   if (fes->mesh) {
     Mesh *me = NULL;
-    MVert *mvert = NULL;
     const MLoopTri *looptri;
-    const MLoop *mloop;
     BVHTreeFromMesh tree_data = {NULL};
     int numverts, i;
 
@@ -1008,13 +1007,9 @@ static void obstacles_from_mesh(Object *coll_ob,
     int min[3], max[3], res[3];
 
     /* Duplicate vertices to modify. */
-    if (me->mvert) {
-      me->mvert = MEM_dupallocN(me->mvert);
-      CustomData_set_layer(&me->vdata, CD_MVERT, me->mvert);
-    }
+    MVert *verts = MEM_dupallocN(BKE_mesh_vertices(me));
 
-    mvert = me->mvert;
-    mloop = me->mloop;
+    const MLoop *mloop = BKE_mesh_loops(me);
     looptri = BKE_mesh_runtime_looptri_ensure(me);
     numverts = me->totvert;
 
@@ -1041,11 +1036,11 @@ static void obstacles_from_mesh(Object *coll_ob,
       float co[3];
 
       /* Vertex position. */
-      mul_m4_v3(coll_ob->obmat, mvert[i].co);
-      manta_pos_to_cell(fds, mvert[i].co);
+      mul_m4_v3(coll_ob->obmat, verts[i].co);
+      manta_pos_to_cell(fds, verts[i].co);
 
       /* Vertex velocity. */
-      add_v3fl_v3fl_v3i(co, mvert[i].co, fds->shift);
+      add_v3fl_v3fl_v3i(co, verts[i].co, fds->shift);
       if (has_velocity) {
         sub_v3_v3v3(&vert_vel[i * 3], co, &fes->verts_old[i * 3]);
         mul_v3_fl(&vert_vel[i * 3], 1.0f / dt);
@@ -1053,7 +1048,7 @@ static void obstacles_from_mesh(Object *coll_ob,
       copy_v3_v3(&fes->verts_old[i * 3], co);
 
       /* Calculate emission map bounds. */
-      bb_boundInsert(bb, mvert[i].co);
+      bb_boundInsert(bb, verts[i].co);
     }
 
     /* Set emission map.
@@ -1075,7 +1070,7 @@ static void obstacles_from_mesh(Object *coll_ob,
 
       ObstaclesFromDMData data = {
           .fes = fes,
-          .mvert = mvert,
+          .mvert = verts,
           .mloop = mloop,
           .mlooptri = looptri,
           .tree = &tree_data,
@@ -1098,9 +1093,7 @@ static void obstacles_from_mesh(Object *coll_ob,
     if (vert_vel) {
       MEM_freeN(vert_vel);
     }
-    if (me->mvert) {
-      MEM_freeN(me->mvert);
-    }
+    MEM_SAFE_FREE(verts);
     BKE_id_free(NULL, me);
   }
 }
@@ -2080,16 +2073,12 @@ static void emit_from_mesh(
     Mesh *me = BKE_mesh_copy_for_eval(ffs->mesh, true);
 
     /* Duplicate vertices to modify. */
-    if (me->mvert) {
-      me->mvert = MEM_dupallocN(me->mvert);
-      CustomData_set_layer(&me->vdata, CD_MVERT, me->mvert);
-    }
+    MVert *verts = MEM_dupallocN(BKE_mesh_vertices(me));
 
-    MVert *mvert = me->mvert;
-    const MLoop *mloop = me->mloop;
+    const MLoop *mloop = BKE_mesh_loops(me);
     const MLoopTri *mlooptri = BKE_mesh_runtime_looptri_ensure(me);
     const int numverts = me->totvert;
-    const MDeformVert *dvert = CustomData_get_layer(&me->vdata, CD_MDEFORMVERT);
+    const MDeformVert *dvert = BKE_mesh_deform_verts(me);
     const MLoopUV *mloopuv = CustomData_get_layer_named(&me->ldata, CD_MLOOPUV, ffs->uvlayer_name);
 
     if (ffs->flags & FLUID_FLOW_INITVELOCITY) {
@@ -2109,12 +2098,11 @@ static void emit_from_mesh(
 
     /* Transform mesh vertices to domain grid space for fast lookups.
      * This is valid because the mesh is copied above. */
-    BKE_mesh_vertex_normals_ensure(me);
-    float(*vert_normals)[3] = BKE_mesh_vertex_normals_for_write(me);
+    float(*vert_normals)[3] = MEM_dupallocN(BKE_mesh_vertex_normals_ensure(me));
     for (i = 0; i < numverts; i++) {
       /* Vertex position. */
-      mul_m4_v3(flow_ob->obmat, mvert[i].co);
-      manta_pos_to_cell(fds, mvert[i].co);
+      mul_m4_v3(flow_ob->obmat, verts[i].co);
+      manta_pos_to_cell(fds, verts[i].co);
 
       /* Vertex normal. */
       mul_mat3_m4_v3(flow_ob->obmat, vert_normals[i]);
@@ -2124,7 +2112,7 @@ static void emit_from_mesh(
       /* Vertex velocity. */
       if (ffs->flags & FLUID_FLOW_INITVELOCITY) {
         float co[3];
-        add_v3fl_v3fl_v3i(co, mvert[i].co, fds->shift);
+        add_v3fl_v3fl_v3i(co, verts[i].co, fds->shift);
         if (has_velocity) {
           sub_v3_v3v3(&vert_vel[i * 3], co, &ffs->verts_old[i * 3]);
           mul_v3_fl(&vert_vel[i * 3], 1.0 / dt);
@@ -2133,7 +2121,7 @@ static void emit_from_mesh(
       }
 
       /* Calculate emission map bounds. */
-      bb_boundInsert(bb, mvert[i].co);
+      bb_boundInsert(bb, verts[i].co);
     }
     mul_m4_v3(flow_ob->obmat, flow_center);
     manta_pos_to_cell(fds, flow_center);
@@ -2158,7 +2146,7 @@ static void emit_from_mesh(
       EmitFromDMData data = {
           .fds = fds,
           .ffs = ffs,
-          .mvert = mvert,
+          .mvert = verts,
           .vert_normals = vert_normals,
           .mloop = mloop,
           .mlooptri = mlooptri,
@@ -2186,9 +2174,8 @@ static void emit_from_mesh(
     if (vert_vel) {
       MEM_freeN(vert_vel);
     }
-    if (me->mvert) {
-      MEM_freeN(me->mvert);
-    }
+    MEM_SAFE_FREE(verts);
+    MEM_SAFE_FREE(vert_normals);
     BKE_id_free(NULL, me);
   }
 }
@@ -3241,7 +3228,7 @@ static Mesh *create_liquid_geometry(FluidDomainSettings *fds,
    * If there are no faces in original mesh, keep materials and flags unchanged. */
   MPoly *mpoly;
   MPoly mp_example = {0};
-  mpoly = orgmesh->mpoly;
+  mpoly = BKE_mesh_polygons_for_write(orgmesh);
   if (mpoly) {
     mp_example = *mpoly;
   }
@@ -3273,9 +3260,9 @@ static Mesh *create_liquid_geometry(FluidDomainSettings *fds,
   if (!me) {
     return NULL;
   }
-  mverts = me->mvert;
-  mpolys = me->mpoly;
-  mloops = me->mloop;
+  mverts = BKE_mesh_vertices_for_write(me);
+  mpolys = BKE_mesh_polygons_for_write(me);
+  mloops = BKE_mesh_loops_for_write(me);
 
   /* Get size (dimension) but considering scaling. */
   copy_v3_v3(cell_size_scaled, fds->cell_size);
@@ -3409,9 +3396,9 @@ static Mesh *create_smoke_geometry(FluidDomainSettings *fds, Mesh *orgmesh, Obje
   }
 
   result = BKE_mesh_new_nomain(num_verts, 0, 0, num_faces * 4, num_faces);
-  mverts = result->mvert;
-  mpolys = result->mpoly;
-  mloops = result->mloop;
+  mverts = BKE_mesh_vertices_for_write(result);
+  mpolys = BKE_mesh_polygons_for_write(result);
+  mloops = BKE_mesh_loops_for_write(result);
 
   if (num_verts) {
     /* Volume bounds. */