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, 22 insertions, 14 deletions

diff --git a/source/blender/blenkernel/intern/subdiv_converter_mesh.c b/source/blender/blenkernel/intern/subdiv_converter_mesh.c
index 9c6d507d42c..f908e1af4ac 100644
--- a/source/blender/blenkernel/intern/subdiv_converter_mesh.c
+++ b/source/blender/blenkernel/intern/subdiv_converter_mesh.c
@@ -16,6 +16,7 @@
 #include "BLI_utildefines.h"
 
 #include "BKE_customdata.h"
+#include "BKE_mesh.h"
 #include "BKE_mesh_mapping.h"
 #include "BKE_subdiv.h"
 
@@ -33,6 +34,11 @@
 typedef struct ConverterStorage {
   SubdivSettings settings;
   const Mesh *mesh;
+  const MVert *verts;
+  const MEdge *edges;
+  const MPoly *polys;
+  const MLoop *loops;
+
   /* CustomData layer for vertex sharpnesses. */
   const float *cd_vertex_crease;
   /* Indexed by loop index, value denotes index of face-varying vertex
@@ -116,7 +122,7 @@ static int get_num_vertices(const OpenSubdiv_Converter *converter)
 static int get_num_face_vertices(const OpenSubdiv_Converter *converter, int manifold_face_index)
 {
   ConverterStorage *storage = converter->user_data;
-  return storage->mesh->mpoly[manifold_face_index].totloop;
+  return storage->polys[manifold_face_index].totloop;
 }
 
 static void get_face_vertices(const OpenSubdiv_Converter *converter,
@@ -124,8 +130,8 @@ static void get_face_vertices(const OpenSubdiv_Converter *converter,
                               int *manifold_face_vertices)
 {
   ConverterStorage *storage = converter->user_data;
-  const MPoly *poly = &storage->mesh->mpoly[manifold_face_index];
-  const MLoop *mloop = storage->mesh->mloop;
+  const MPoly *poly = &storage->polys[manifold_face_index];
+  const MLoop *mloop = storage->loops;
   for (int corner = 0; corner < poly->totloop; corner++) {
     manifold_face_vertices[corner] =
         storage->manifold_vertex_index[mloop[poly->loopstart + corner].v];
@@ -138,7 +144,7 @@ static void get_edge_vertices(const OpenSubdiv_Converter *converter,
 {
   ConverterStorage *storage = converter->user_data;
   const int edge_index = storage->manifold_edge_index_reverse[manifold_edge_index];
-  const MEdge *edge = &storage->mesh->medge[edge_index];
+  const MEdge *edge = &storage->edges[edge_index];
   manifold_edge_vertices[0] = storage->manifold_vertex_index[edge->v1];
   manifold_edge_vertices[1] = storage->manifold_vertex_index[edge->v2];
 }
@@ -155,7 +161,7 @@ static float get_edge_sharpness(const OpenSubdiv_Converter *converter, int manif
     return 0.0f;
   }
   const int edge_index = storage->manifold_edge_index_reverse[manifold_edge_index];
-  const MEdge *medge = storage->mesh->medge;
+  const MEdge *medge = storage->edges;
   return BKE_subdiv_crease_to_sharpness_char(medge[edge_index].crease);
 }
 
@@ -193,8 +199,6 @@ static void precalc_uv_layer(const OpenSubdiv_Converter *converter, const int la
 {
   ConverterStorage *storage = converter->user_data;
   const Mesh *mesh = storage->mesh;
-  const MPoly *mpoly = mesh->mpoly;
-  const MLoop *mloop = mesh->mloop;
   const MLoopUV *mloopuv = CustomData_get_layer_n(&mesh->ldata, CD_MLOOPUV, layer_index);
   const int num_poly = mesh->totpoly;
   const int num_vert = mesh->totvert;
@@ -205,9 +209,9 @@ static void precalc_uv_layer(const OpenSubdiv_Converter *converter, const int la
         mesh->totloop, sizeof(int), "loop uv vertex index");
   }
   UvVertMap *uv_vert_map = BKE_mesh_uv_vert_map_create(
-      mpoly,
+      storage->polys,
       (const bool *)CustomData_get_layer_named(&mesh->pdata, CD_PROP_BOOL, ".hide_poly"),
-      mloop,
+      storage->loops,
       mloopuv,
       num_poly,
       num_vert,
@@ -222,7 +226,7 @@ static void precalc_uv_layer(const OpenSubdiv_Converter *converter, const int la
       if (uv_vert->separate) {
         storage->num_uv_coordinates++;
       }
-      const MPoly *mp = &mpoly[uv_vert->poly_index];
+      const MPoly *mp = &storage->polys[uv_vert->poly_index];
       const int global_loop_index = mp->loopstart + uv_vert->loop_of_poly_index;
       storage->loop_uv_indices[global_loop_index] = storage->num_uv_coordinates;
       uv_vert = uv_vert->next;
@@ -250,7 +254,7 @@ static int get_face_corner_uv_index(const OpenSubdiv_Converter *converter,
                                     const int corner)
 {
   ConverterStorage *storage = converter->user_data;
-  const MPoly *mp = &storage->mesh->mpoly[face_index];
+  const MPoly *mp = &storage->polys[face_index];
   return storage->loop_uv_indices[mp->loopstart + corner];
 }
 
@@ -344,9 +348,9 @@ static void initialize_manifold_index_array(const BLI_bitmap *used_map,
 static void initialize_manifold_indices(ConverterStorage *storage)
 {
   const Mesh *mesh = storage->mesh;
-  const MEdge *medge = mesh->medge;
-  const MLoop *mloop = mesh->mloop;
-  const MPoly *mpoly = mesh->mpoly;
+  const MEdge *medge = storage->edges;
+  const MLoop *mloop = storage->loops;
+  const MPoly *mpoly = storage->polys;
   /* Set bits of elements which are not loose. */
   BLI_bitmap *vert_used_map = BLI_BITMAP_NEW(mesh->totvert, "vert used map");
   BLI_bitmap *edge_used_map = BLI_BITMAP_NEW(mesh->totedge, "edge used map");
@@ -389,6 +393,10 @@ static void init_user_data(OpenSubdiv_Converter *converter,
   ConverterStorage *user_data = MEM_mallocN(sizeof(ConverterStorage), __func__);
   user_data->settings = *settings;
   user_data->mesh = mesh;
+  user_data->verts = BKE_mesh_vertices(mesh);
+  user_data->edges = BKE_mesh_edges(mesh);
+  user_data->polys = BKE_mesh_polygons(mesh);
+  user_data->loops = BKE_mesh_loops(mesh);
   user_data->cd_vertex_crease = CustomData_get_layer(&mesh->vdata, CD_CREASE);
   user_data->loop_uv_indices = NULL;
   initialize_manifold_indices(user_data);