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, 55 insertions, 50 deletions

diff --git a/source/blender/editors/mesh/mesh_data.cc b/source/blender/editors/mesh/mesh_data.cc
index 1511da810cb..09673b3d7ad 100644
--- a/source/blender/editors/mesh/mesh_data.cc
+++ b/source/blender/editors/mesh/mesh_data.cc
@@ -18,6 +18,7 @@
 #include "BLI_utildefines.h"
 
 #include "BKE_attribute.h"
+#include "BKE_attribute.hh"
 #include "BKE_context.h"
 #include "BKE_customdata.h"
 #include "BKE_editmesh.h"
@@ -44,6 +45,8 @@
 #include "mesh_intern.h" /* own include */
 
 using blender::Array;
+using blender::MutableSpan;
+using blender::Span;
 
 static CustomData *mesh_customdata_get_type(Mesh *me, const char htype, int *r_tot)
 {
@@ -128,7 +131,6 @@ static void delete_customdata_layer(Mesh *me, CustomDataLayer *layer)
   }
   else {
     CustomData_free_layer(data, type, tot, layer_index + n);
-    BKE_mesh_update_customdata_pointers(me, true);
   }
 }
 
@@ -186,7 +188,7 @@ static void mesh_uv_reset_bmface(BMFace *f, const int cd_loop_uv_offset)
   mesh_uv_reset_array(fuv.data(), f->len);
 }
 
-static void mesh_uv_reset_mface(MPoly *mp, MLoopUV *mloopuv)
+static void mesh_uv_reset_mface(const MPoly *mp, MLoopUV *mloopuv)
 {
   Array<float *, BM_DEFAULT_NGON_STACK_SIZE> fuv(mp->totloop);
 
@@ -223,8 +225,9 @@ void ED_mesh_uv_loop_reset_ex(Mesh *me, const int layernum)
     BLI_assert(CustomData_has_layer(&me->ldata, CD_MLOOPUV));
     MLoopUV *mloopuv = (MLoopUV *)CustomData_get_layer_n(&me->ldata, CD_MLOOPUV, layernum);
 
+    const MPoly *polys = BKE_mesh_polygons(me);
     for (int i = 0; i < me->totpoly; i++) {
-      mesh_uv_reset_mface(&me->mpoly[i], mloopuv);
+      mesh_uv_reset_mface(&polys[i], mloopuv);
     }
   }
 
@@ -280,9 +283,13 @@ int ED_mesh_uv_add(
       return -1;
     }
 
-    if (me->mloopuv && do_init) {
-      CustomData_add_layer_named(
-          &me->ldata, CD_MLOOPUV, CD_DUPLICATE, me->mloopuv, me->totloop, name);
+    if (CustomData_has_layer(&me->ldata, CD_MLOOPUV) && do_init) {
+      CustomData_add_layer_named(&me->ldata,
+                                 CD_MLOOPUV,
+                                 CD_DUPLICATE,
+                                 CustomData_get_layer(&me->ldata, CD_MLOOPUV),
+                                 me->totloop,
+                                 name);
       is_init = true;
     }
     else {
@@ -293,8 +300,6 @@ int ED_mesh_uv_add(
     if (active_set || layernum_dst == 0) {
       CustomData_set_layer_active(&me->ldata, CD_MLOOPUV, layernum_dst);
     }
-
-    BKE_mesh_update_customdata_pointers(me, true);
   }
 
   /* don't overwrite our copied coords */
@@ -399,9 +404,13 @@ int ED_mesh_color_add(Mesh *me,
   else {
     layernum = CustomData_number_of_layers(&me->ldata, CD_PROP_BYTE_COLOR);
 
-    if (me->mloopcol && do_init) {
-      CustomData_add_layer_named(
-          &me->ldata, CD_PROP_BYTE_COLOR, CD_DUPLICATE, me->mloopcol, me->totloop, name);
+    if (CustomData_get_active_layer(&me->ldata, CD_PROP_BYTE_COLOR) != -1 && do_init) {
+      CustomData_add_layer_named(&me->ldata,
+                                 CD_PROP_BYTE_COLOR,
+                                 CD_DUPLICATE,
+                                 CustomData_get_layer(&me->ldata, CD_PROP_BYTE_COLOR),
+                                 me->totloop,
+                                 name);
     }
     else {
       CustomData_add_layer_named(
@@ -412,7 +421,7 @@ int ED_mesh_color_add(Mesh *me,
       CustomData_set_layer_active(&me->ldata, CD_PROP_BYTE_COLOR, layernum);
     }
 
-    BKE_mesh_update_customdata_pointers(me, true);
+    BKE_mesh_tessface_clear(me);
   }
 
   DEG_id_tag_update(&me->id, 0);
@@ -432,7 +441,7 @@ bool ED_mesh_color_ensure(Mesh *me, const char *name)
     layer = me->ldata.layers + CustomData_get_layer_index(&me->ldata, CD_PROP_BYTE_COLOR);
 
     BKE_id_attributes_active_color_set(&me->id, layer);
-    BKE_mesh_update_customdata_pointers(me, true);
+    BKE_mesh_tessface_clear(me);
   }
 
   DEG_id_tag_update(&me->id, 0);
@@ -496,7 +505,7 @@ int ED_mesh_sculpt_color_add(Mesh *me,
       CustomData_set_layer_active(&me->vdata, CD_PROP_COLOR, layernum);
     }
 
-    BKE_mesh_update_customdata_pointers(me, true);
+    BKE_mesh_tessface_clear(me);
   }
 
   DEG_id_tag_update(&me->id, 0);
@@ -767,15 +776,20 @@ static int mesh_customdata_custom_splitnormals_add_exec(bContext *C, wmOperator
       /* Tag edges as sharp according to smooth threshold if needed,
        * to preserve autosmooth shading. */
       if (me->flag & ME_AUTOSMOOTH) {
-        BKE_edges_sharp_from_angle_set(me->mvert,
-                                       me->totvert,
-                                       me->medge,
-                                       me->totedge,
-                                       me->mloop,
-                                       me->totloop,
-                                       me->mpoly,
+        const Span<MVert> verts = me->vertices();
+        MutableSpan<MEdge> edges = me->edges_for_write();
+        const Span<MPoly> polys = me->polygons();
+        const Span<MLoop> loops = me->loops();
+
+        BKE_edges_sharp_from_angle_set(verts.data(),
+                                       verts.size(),
+                                       edges.data(),
+                                       edges.size(),
+                                       loops.data(),
+                                       loops.size(),
+                                       polys.data(),
                                        BKE_mesh_poly_normals_ensure(me),
-                                       me->totpoly,
+                                       polys.size(),
                                        me->smoothresh);
       }
 
@@ -873,27 +887,22 @@ static void mesh_add_verts(Mesh *mesh, int len)
 
   CustomData_free(&mesh->vdata, mesh->totvert);
   mesh->vdata = vdata;
-  BKE_mesh_update_customdata_pointers(mesh, false);
 
   BKE_mesh_runtime_clear_cache(mesh);
 
-  /* scan the input list and insert the new vertices */
+  const int old_vertex_num = mesh->totvert;
+  mesh->totvert = totvert;
 
-  /* set default flags */
-  MVert *mvert = &mesh->mvert[mesh->totvert];
-  for (int i = 0; i < len; i++, mvert++) {
-    mvert->flag |= SELECT;
+  MutableSpan<MVert> verts = mesh->vertices_for_write();
+  for (MVert &vert : verts.drop_front(old_vertex_num)) {
+    vert.flag = SELECT;
   }
-
-  /* set final vertex list size */
-  mesh->totvert = totvert;
 }
 
 static void mesh_add_edges(Mesh *mesh, int len)
 {
   CustomData edata;
-  MEdge *medge;
-  int i, totedge;
+  int totedge;
 
   if (len == 0) {
     return;
@@ -911,17 +920,16 @@ static void mesh_add_edges(Mesh *mesh, int len)
 
   CustomData_free(&mesh->edata, mesh->totedge);
   mesh->edata = edata;
-  BKE_mesh_update_customdata_pointers(mesh, false); /* new edges don't change tessellation */
 
   BKE_mesh_runtime_clear_cache(mesh);
 
-  /* set default flags */
-  medge = &mesh->medge[mesh->totedge];
-  for (i = 0; i < len; i++, medge++) {
-    medge->flag = ME_EDGEDRAW | ME_EDGERENDER | SELECT;
-  }
-
+  const int old_edges_num = mesh->totedge;
   mesh->totedge = totedge;
+
+  MutableSpan<MEdge> edges = mesh->edges_for_write();
+  for (MEdge &edge : edges.drop_front(old_edges_num)) {
+    edge.flag = ME_EDGEDRAW | ME_EDGERENDER | SELECT;
+  }
 }
 
 static void mesh_add_loops(Mesh *mesh, int len)
@@ -947,7 +955,6 @@ static void mesh_add_loops(Mesh *mesh, int len)
 
   CustomData_free(&mesh->ldata, mesh->totloop);
   mesh->ldata = ldata;
-  BKE_mesh_update_customdata_pointers(mesh, true);
 
   mesh->totloop = totloop;
 }
@@ -955,8 +962,7 @@ static void mesh_add_loops(Mesh *mesh, int len)
 static void mesh_add_polys(Mesh *mesh, int len)
 {
   CustomData pdata;
-  MPoly *mpoly;
-  int i, totpoly;
+  int totpoly;
 
   if (len == 0) {
     return;
@@ -974,17 +980,16 @@ static void mesh_add_polys(Mesh *mesh, int len)
 
   CustomData_free(&mesh->pdata, mesh->totpoly);
   mesh->pdata = pdata;
-  BKE_mesh_update_customdata_pointers(mesh, true);
 
   BKE_mesh_runtime_clear_cache(mesh);
 
-  /* set default flags */
-  mpoly = &mesh->mpoly[mesh->totpoly];
-  for (i = 0; i < len; i++, mpoly++) {
-    mpoly->flag = ME_FACE_SEL;
-  }
-
+  const int old_polys_num = mesh->totpoly;
   mesh->totpoly = totpoly;
+
+  MutableSpan<MPoly> polys = mesh->polygons_for_write();
+  for (MPoly &poly : polys.drop_front(old_polys_num)) {
+    poly.flag = ME_FACE_SEL;
+  }
 }
 
 /* -------------------------------------------------------------------- */