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, 25 insertions, 21 deletions

diff --git a/source/blender/blenkernel/intern/particle.c b/source/blender/blenkernel/intern/particle.c
index 9ccd6562649..8db83031e17 100644
--- a/source/blender/blenkernel/intern/particle.c
+++ b/source/blender/blenkernel/intern/particle.c
@@ -1399,7 +1399,8 @@ static void init_particle_interpolation(Object *ob,
     pind->dietime = (key + pa->totkey - 1)->time;
 
     if (pind->mesh) {
-      pind->mvert[0] = &pind->mesh->mvert[pa->hair_index];
+      MVert *verts = BKE_mesh_vertices_for_write(pind->mesh);
+      pind->mvert[0] = &verts[pa->hair_index];
       pind->mvert[1] = pind->mvert[0] + 1;
     }
   }
@@ -1664,7 +1665,7 @@ static void interpolate_pathcache(ParticleCacheKey *first, float t, ParticleCach
 /************************************************/
 
 void psys_interpolate_face(Mesh *mesh,
-                           MVert *mvert,
+                           const MVert *mvert,
                            const float (*vert_normals)[3],
                            MFace *mface,
                            MTFace *tface,
@@ -1676,7 +1677,7 @@ void psys_interpolate_face(Mesh *mesh,
                            float vtan[3],
                            float orco[3])
 {
-  float *v1 = 0, *v2 = 0, *v3 = 0, *v4 = 0;
+  const float *v1 = 0, *v2 = 0, *v3 = 0, *v4 = 0;
   float e1[3], e2[3], s1, s2, t1, t2;
   float *uv1, *uv2, *uv3, *uv4;
   float n1[3], n2[3], n3[3], n4[3];
@@ -1852,7 +1853,8 @@ static float psys_interpolate_value_from_verts(
       return values[index];
     case PART_FROM_FACE:
     case PART_FROM_VOLUME: {
-      MFace *mf = &mesh->mface[index];
+      MFace *mfaces = CustomData_get_layer(&mesh->fdata, CD_MFACE);
+      MFace *mf = &mfaces[index];
       return interpolate_particle_value(
           values[mf->v1], values[mf->v2], values[mf->v3], values[mf->v4], fw, mf->v4);
     }
@@ -1941,7 +1943,7 @@ int psys_particle_dm_face_lookup(Mesh *mesh_final,
 
   index_mf_to_mpoly_deformed = NULL;
 
-  mtessface_final = mesh_final->mface;
+  mtessface_final = CustomData_get_layer(&mesh_final->fdata, CD_MFACE);
   osface_final = CustomData_get_layer(&mesh_final->fdata, CD_ORIGSPACE);
 
   if (osface_final == NULL) {
@@ -2061,7 +2063,8 @@ static int psys_map_index_on_dm(Mesh *mesh,
       /* modify the original weights to become
        * weights for the derived mesh face */
       OrigSpaceFace *osface = CustomData_get_layer(&mesh->fdata, CD_ORIGSPACE);
-      const MFace *mface = &mesh->mface[i];
+      const MFace *mfaces = CustomData_get_layer(&mesh->fdata, CD_MFACE);
+      const MFace *mface = &mfaces[i];
 
       if (osface == NULL) {
         mapfw[0] = mapfw[1] = mapfw[2] = mapfw[3] = 0.0f;
@@ -2117,7 +2120,8 @@ void psys_particle_on_dm(Mesh *mesh_final,
   const float(*vert_normals)[3] = BKE_mesh_vertex_normals_ensure(mesh_final);
 
   if (from == PART_FROM_VERT) {
-    copy_v3_v3(vec, mesh_final->mvert[mapindex].co);
+    const MVert *vertices = BKE_mesh_vertices(mesh_final);
+    copy_v3_v3(vec, vertices[mapindex].co);
 
     if (nor) {
       copy_v3_v3(nor, vert_normals[mapindex]);
@@ -2143,9 +2147,10 @@ void psys_particle_on_dm(Mesh *mesh_final,
     MTFace *mtface;
     MVert *mvert;
 
-    mface = &mesh_final->mface[mapindex];
-    mvert = mesh_final->mvert;
-    mtface = mesh_final->mtface;
+    MFace *mfaces = CustomData_get_layer(&mesh_final->fdata, CD_MFACE);
+    mface = &mfaces[mapindex];
+    mvert = BKE_mesh_vertices_for_write(mesh_final);
+    mtface = CustomData_get_layer(&mesh_final->fdata, CD_MTFACE);
 
     if (mtface) {
       mtface += mapindex;
@@ -2634,7 +2639,7 @@ float *psys_cache_vgroup(Mesh *mesh, ParticleSystem *psys, int vgroup)
     /* hair dynamics pinning vgroup */
   }
   else if (psys->vgroup[vgroup]) {
-    MDeformVert *dvert = mesh->dvert;
+    const MDeformVert *dvert = BKE_mesh_deform_verts(mesh);
     if (dvert) {
       int totvert = mesh->totvert, i;
       vg = MEM_callocN(sizeof(float) * totvert, "vg_cache");
@@ -3848,7 +3853,8 @@ static void psys_face_mat(Object *ob, Mesh *mesh, ParticleData *pa, float mat[4]
     return;
   }
 
-  mface = &mesh->mface[i];
+  MFace *mfaces = CustomData_get_layer(&mesh->fdata, CD_MFACE);
+  mface = &mfaces[i];
   const OrigSpaceFace *osface = CustomData_get(&mesh->fdata, i, CD_ORIGSPACE);
 
   if (orco && (orcodata = CustomData_get_layer(&mesh->vdata, CD_ORCO))) {
@@ -3863,9 +3869,10 @@ static void psys_face_mat(Object *ob, Mesh *mesh, ParticleData *pa, float mat[4]
     }
   }
   else {
-    copy_v3_v3(v[0], mesh->mvert[mface->v1].co);
-    copy_v3_v3(v[1], mesh->mvert[mface->v2].co);
-    copy_v3_v3(v[2], mesh->mvert[mface->v3].co);
+    const MVert *verts = BKE_mesh_vertices(mesh);
+    copy_v3_v3(v[0], verts[mface->v1].co);
+    copy_v3_v3(v[1], verts[mface->v2].co);
+    copy_v3_v3(v[2], verts[mface->v3].co);
   }
 
   triatomat(v[0], v[1], v[2], (osface) ? osface->uv : NULL, mat);
@@ -4155,6 +4162,7 @@ static int get_particle_uv(Mesh *mesh,
                            float *texco,
                            bool from_vert)
 {
+  MFace *mfaces = (MFace *)CustomData_get_layer(&mesh->fdata, CD_MFACE);
   MFace *mf;
   const MTFace *tf;
   int i;
@@ -4162,10 +4170,6 @@ static int get_particle_uv(Mesh *mesh,
   tf = CustomData_get_layer_named(&mesh->fdata, CD_MTFACE, name);
 
   if (tf == NULL) {
-    tf = mesh->mtface;
-  }
-
-  if (tf == NULL) {
     return 0;
   }
 
@@ -4186,7 +4190,7 @@ static int get_particle_uv(Mesh *mesh,
   }
   else {
     if (from_vert) {
-      mf = mesh->mface;
+      mf = mfaces;
 
       /* This finds the first face to contain the emitting vertex,
        * this is not ideal, but is mostly fine as UV seams generally
@@ -4199,7 +4203,7 @@ static int get_particle_uv(Mesh *mesh,
       }
     }
     else {
-      mf = &mesh->mface[i];
+      mf = &mfaces[i];
     }
 
     psys_interpolate_uvs(&tf[i], mf->v4, fuv, texco);