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, 12 insertions, 11 deletions

diff --git a/source/blender/blenkernel/intern/shrinkwrap.c b/source/blender/blenkernel/intern/shrinkwrap.c
index 82cc250c6d1..bea2f8f3c4f 100644
--- a/source/blender/blenkernel/intern/shrinkwrap.c
+++ b/source/blender/blenkernel/intern/shrinkwrap.c
@@ -64,9 +64,9 @@ typedef struct ShrinkwrapCalcData {
   float (*vertexCos)[3]; /* vertexs being shrinkwraped */
   int numVerts;
 
-  struct MDeformVert *dvert; /* Pointer to mdeform array */
-  int vgroup;                /* Vertex group num */
-  bool invert_vgroup;        /* invert vertex group influence */
+  const struct MDeformVert *dvert; /* Pointer to mdeform array */
+  int vgroup;                      /* Vertex group num */
+  bool invert_vgroup;              /* invert vertex group influence */
 
   struct Mesh *target;                /* mesh we are shrinking to */
   struct SpaceTransform local2target; /* transform to move between local and target space */
@@ -113,6 +113,7 @@ bool BKE_shrinkwrap_init_tree(
   }
 
   data->mesh = mesh;
+  data->polys = BKE_mesh_polygons(mesh);
 
   if (shrinkType == MOD_SHRINKWRAP_NEAREST_VERTEX) {
     data->bvh = BKE_bvhtree_from_mesh_get(&data->treeData, mesh, BVHTREE_FROM_VERTS, 2);
@@ -191,9 +192,9 @@ static void merge_vert_dir(ShrinkwrapBoundaryVertData *vdata,
 
 static ShrinkwrapBoundaryData *shrinkwrap_build_boundary_data(struct Mesh *mesh)
 {
-  const MLoop *mloop = mesh->mloop;
-  const MEdge *medge = mesh->medge;
-  const MVert *mvert = mesh->mvert;
+  const MVert *mvert = BKE_mesh_vertices(mesh);
+  const MEdge *medge = BKE_mesh_edges(mesh);
+  const MLoop *mloop = BKE_mesh_loops(mesh);
 
   /* Count faces per edge (up to 2). */
   char *edge_mode = MEM_calloc_arrayN((size_t)mesh->totedge, sizeof(char), __func__);
@@ -937,7 +938,7 @@ static void target_project_edge(const ShrinkwrapTreeData *tree,
                                 int eidx)
 {
   const BVHTreeFromMesh *data = &tree->treeData;
-  const MEdge *edge = &tree->mesh->medge[eidx];
+  const MEdge *edge = &data->edge[eidx];
   const float *vedge_co[2] = {data->vert[edge->v1].co, data->vert[edge->v2].co};
 
 #ifdef TRACE_TARGET_PROJECT
@@ -1179,7 +1180,7 @@ void BKE_shrinkwrap_compute_smooth_normal(const struct ShrinkwrapTreeData *tree,
   const float(*vert_normals)[3] = tree->treeData.vert_normals;
 
   /* Interpolate smooth normals if enabled. */
-  if ((tree->mesh->mpoly[tri->poly].flag & ME_SMOOTH) != 0) {
+  if ((tree->polys[tri->poly].flag & ME_SMOOTH) != 0) {
     const uint32_t vert_indices[3] = {treeData->loop[tri->tri[0]].v,
                                       treeData->loop[tri->tri[1]].v,
                                       treeData->loop[tri->tri[2]].v};
@@ -1369,7 +1370,7 @@ void shrinkwrapModifier_deform(ShrinkwrapModifierData *smd,
                                struct Scene *scene,
                                Object *ob,
                                Mesh *mesh,
-                               MDeformVert *dvert,
+                               const MDeformVert *dvert,
                                const int defgrp_index,
                                float (*vertexCos)[3],
                                int numVerts)
@@ -1411,7 +1412,7 @@ void shrinkwrapModifier_deform(ShrinkwrapModifierData *smd,
 
   if (mesh != NULL && smd->shrinkType == MOD_SHRINKWRAP_PROJECT) {
     /* Setup arrays to get vertexs positions, normals and deform weights */
-    calc.vert = mesh->mvert;
+    calc.vert = BKE_mesh_vertices_for_write(mesh);
     calc.vert_normals = BKE_mesh_vertex_normals_ensure(mesh);
 
     /* Using vertexs positions/normals as if a subsurface was applied */
@@ -1574,7 +1575,7 @@ void BKE_shrinkwrap_remesh_target_project(Mesh *src_me, Mesh *target_me, Object
   calc.vgroup = -1;
   calc.target = target_me;
   calc.keepDist = ssmd.keepDist;
-  calc.vert = src_me->mvert;
+  calc.vert = BKE_mesh_vertices_for_write(src_me);
   BLI_SPACE_TRANSFORM_SETUP(&calc.local2target, ob_target, ob_target);
 
   ShrinkwrapTreeData tree;