Attributes: Improve custom data initialization options

When allocating new `CustomData` layers, often we do redundant
initialization of arrays. For example, it's common that values are
allocated, set to their default value, and then set to some other
value. This is wasteful, and it negates the benefits of optimizations
to the allocator like D15082. There are two reasons for this. The
first is array-of-structs storage that makes it annoying to initialize
values manually, and the second is confusing options in the Custom Data
API. This patch addresses the latter.

The `CustomData` "alloc type" options are rearranged. Now, besides
the options that use existing layers, there are two remaining:
* `CD_SET_DEFAULT` sets the default value.
  * Usually zeroes, but for colors this is white (how it was before).
  * Should be used when you add the layer but don't set all values.
* `CD_CONSTRUCT` refers to the "default construct" C++ term.
  * Only necessary or defined for non-trivial types like vertex groups.
  * Doesn't do anything for trivial types like `int` or `float3`.
  * Should be used every other time, when all values will be set.

The attribute API's `AttributeInit` types are updated as well.
To update code, replace `CD_CALLOC` with `CD_SET_DEFAULT` and
`CD_DEFAULT` with `CD_CONSTRUCT`. This doesn't cause any functional
changes yet. Follow-up commits will change to avoid initializing
new layers where the correctness is clear.

Differential Revision: https://developer.blender.org/D15617

7 files changed, 20 insertions, 18 deletions

diff --git a/source/blender/io/alembic/intern/abc_customdata.cc b/source/blender/io/alembic/intern/abc_customdata.cc
index 2820a128072..644990afb35 100644
--- a/source/blender/io/alembic/intern/abc_customdata.cc
+++ b/source/blender/io/alembic/intern/abc_customdata.cc
@@ -540,7 +540,7 @@ void read_generated_coordinates(const ICompoundProperty &prop,
     cd_data = CustomData_get_layer(&mesh->vdata, CD_ORCO);
   }
   else {
-    cd_data = CustomData_add_layer(&mesh->vdata, CD_ORCO, CD_CALLOC, nullptr, totvert);
+    cd_data = CustomData_add_layer(&mesh->vdata, CD_ORCO, CD_SET_DEFAULT, nullptr, totvert);
   }
 
   float(*orcodata)[3] = static_cast<float(*)[3]>(cd_data);
diff --git a/source/blender/io/alembic/intern/abc_reader_mesh.cc b/source/blender/io/alembic/intern/abc_reader_mesh.cc
index bacc1f06599..e18770f2bef 100644
--- a/source/blender/io/alembic/intern/abc_reader_mesh.cc
+++ b/source/blender/io/alembic/intern/abc_reader_mesh.cc
@@ -391,7 +391,7 @@ static void *add_customdata_cb(Mesh *mesh, const char *name, int data_type)
   /* Create a new layer. */
   int numloops = mesh->totloop;
   cd_ptr = CustomData_add_layer_named(
-      &mesh->ldata, cd_data_type, CD_DEFAULT, nullptr, numloops, name);
+      &mesh->ldata, cd_data_type, CD_SET_DEFAULT, nullptr, numloops, name);
   return cd_ptr;
 }
 
@@ -890,7 +890,7 @@ static void read_vertex_creases(Mesh *mesh,
   }
 
   float *vertex_crease_data = (float *)CustomData_add_layer(
-      &mesh->vdata, CD_CREASE, CD_DEFAULT, nullptr, mesh->totvert);
+      &mesh->vdata, CD_CREASE, CD_SET_DEFAULT, nullptr, mesh->totvert);
   const int totvert = mesh->totvert;
 
   for (int i = 0, v = indices->size(); i < v; ++i) {
diff --git a/source/blender/io/collada/MeshImporter.cpp b/source/blender/io/collada/MeshImporter.cpp
index 9fbba1b97fb..34792fd6bb4 100644
--- a/source/blender/io/collada/MeshImporter.cpp
+++ b/source/blender/io/collada/MeshImporter.cpp
@@ -341,7 +341,8 @@ void MeshImporter::read_vertices(COLLADAFW::Mesh *mesh, Mesh *me)
   }
 
   me->totvert = pos.getFloatValues()->getCount() / stride;
-  me->mvert = (MVert *)CustomData_add_layer(&me->vdata, CD_MVERT, CD_CALLOC, nullptr, me->totvert);
+  me->mvert = (MVert *)CustomData_add_layer(
+      &me->vdata, CD_MVERT, CD_SET_DEFAULT, nullptr, me->totvert);
 
   MVert *mvert;
   int i;
@@ -449,9 +450,9 @@ void MeshImporter::allocate_poly_data(COLLADAFW::Mesh *collada_mesh, Mesh *me)
     me->totpoly = total_poly_count;
     me->totloop = total_loop_count;
     me->mpoly = (MPoly *)CustomData_add_layer(
-        &me->pdata, CD_MPOLY, CD_CALLOC, nullptr, me->totpoly);
+        &me->pdata, CD_MPOLY, CD_SET_DEFAULT, nullptr, me->totpoly);
     me->mloop = (MLoop *)CustomData_add_layer(
-        &me->ldata, CD_MLOOP, CD_CALLOC, nullptr, me->totloop);
+        &me->ldata, CD_MLOOP, CD_SET_DEFAULT, nullptr, me->totloop);
 
     unsigned int totuvset = collada_mesh->getUVCoords().getInputInfosArray().getCount();
     for (int i = 0; i < totuvset; i++) {
@@ -468,7 +469,7 @@ void MeshImporter::allocate_poly_data(COLLADAFW::Mesh *collada_mesh, Mesh *me)
         COLLADAFW::String &uvname = info->mName;
         /* Allocate space for UV_data */
         CustomData_add_layer_named(
-            &me->ldata, CD_MLOOPUV, CD_DEFAULT, nullptr, me->totloop, uvname.c_str());
+            &me->ldata, CD_MLOOPUV, CD_SET_DEFAULT, nullptr, me->totloop, uvname.c_str());
       }
       /* activate the first uv map */
       me->mloopuv = (MLoopUV *)CustomData_get_layer_n(&me->ldata, CD_MLOOPUV, 0);
@@ -481,7 +482,7 @@ void MeshImporter::allocate_poly_data(COLLADAFW::Mesh *collada_mesh, Mesh *me)
             collada_mesh->getColors().getInputInfosArray()[i];
         COLLADAFW::String colname = extract_vcolname(info->mName);
         CustomData_add_layer_named(
-            &me->ldata, CD_PROP_BYTE_COLOR, CD_DEFAULT, nullptr, me->totloop, colname.c_str());
+            &me->ldata, CD_PROP_BYTE_COLOR, CD_SET_DEFAULT, nullptr, me->totloop, colname.c_str());
       }
       me->mloopcol = (MLoopCol *)CustomData_get_layer_n(&me->ldata, CD_PROP_BYTE_COLOR, 0);
     }
@@ -546,11 +547,11 @@ void MeshImporter::mesh_add_edges(Mesh *mesh, int len)
   totedge = mesh->totedge + len;
 
   /* Update custom-data. */
-  CustomData_copy(&mesh->edata, &edata, CD_MASK_MESH.emask, CD_DEFAULT, totedge);
+  CustomData_copy(&mesh->edata, &edata, CD_MASK_MESH.emask, CD_SET_DEFAULT, totedge);
   CustomData_copy_data(&mesh->edata, &edata, 0, 0, mesh->totedge);
 
   if (!CustomData_has_layer(&edata, CD_MEDGE)) {
-    CustomData_add_layer(&edata, CD_MEDGE, CD_CALLOC, nullptr, totedge);
+    CustomData_add_layer(&edata, CD_MEDGE, CD_SET_DEFAULT, nullptr, totedge);
   }
 
   CustomData_free(&mesh->edata, mesh->totedge);
diff --git a/source/blender/io/stl/importer/stl_import_mesh.cc b/source/blender/io/stl/importer/stl_import_mesh.cc
index b9ed441f0d9..7686bfa1247 100644
--- a/source/blender/io/stl/importer/stl_import_mesh.cc
+++ b/source/blender/io/stl/importer/stl_import_mesh.cc
@@ -77,7 +77,7 @@ Mesh *STLMeshHelper::to_mesh(Main *bmain, char *mesh_name)
 
   mesh->totvert = verts_.size();
   mesh->mvert = static_cast<MVert *>(
-      CustomData_add_layer(&mesh->vdata, CD_MVERT, CD_CALLOC, nullptr, mesh->totvert));
+      CustomData_add_layer(&mesh->vdata, CD_MVERT, CD_SET_DEFAULT, nullptr, mesh->totvert));
   for (int i = 0; i < mesh->totvert; i++) {
     copy_v3_v3(mesh->mvert[i].co, verts_[i]);
   }
@@ -85,9 +85,9 @@ Mesh *STLMeshHelper::to_mesh(Main *bmain, char *mesh_name)
   mesh->totpoly = tris_.size();
   mesh->totloop = tris_.size() * 3;
   mesh->mpoly = static_cast<MPoly *>(
-      CustomData_add_layer(&mesh->pdata, CD_MPOLY, CD_CALLOC, nullptr, mesh->totpoly));
+      CustomData_add_layer(&mesh->pdata, CD_MPOLY, CD_SET_DEFAULT, nullptr, mesh->totpoly));
   mesh->mloop = static_cast<MLoop *>(
-      CustomData_add_layer(&mesh->ldata, CD_MLOOP, CD_CALLOC, nullptr, mesh->totloop));
+      CustomData_add_layer(&mesh->ldata, CD_MLOOP, CD_SET_DEFAULT, nullptr, mesh->totloop));
 
   threading::parallel_for(tris_.index_range(), 2048, [&](IndexRange tris_range) {
     for (const int i : tris_range) {
diff --git a/source/blender/io/usd/intern/usd_reader_mesh.cc b/source/blender/io/usd/intern/usd_reader_mesh.cc
index 103bb0d0cef..94ff24421e2 100644
--- a/source/blender/io/usd/intern/usd_reader_mesh.cc
+++ b/source/blender/io/usd/intern/usd_reader_mesh.cc
@@ -207,7 +207,8 @@ static void *add_customdata_cb(Mesh *mesh, const char *name, const int data_type
 
   /* Create a new layer. */
   numloops = mesh->totloop;
-  cd_ptr = CustomData_add_layer_named(loopdata, cd_data_type, CD_DEFAULT, nullptr, numloops, name);
+  cd_ptr = CustomData_add_layer_named(
+      loopdata, cd_data_type, CD_SET_DEFAULT, nullptr, numloops, name);
   return cd_ptr;
 }
 
@@ -576,7 +577,7 @@ void USDMeshReader::read_vertex_creases(Mesh *mesh, const double motionSampleTim
   }
 
   float *creases = static_cast<float *>(
-      CustomData_add_layer(&mesh->vdata, CD_CREASE, CD_DEFAULT, nullptr, mesh->totvert));
+      CustomData_add_layer(&mesh->vdata, CD_CREASE, CD_SET_DEFAULT, nullptr, mesh->totvert));
 
   for (size_t i = 0; i < corner_indices.size(); i++) {
     creases[corner_indices[i]] = corner_sharpnesses[i];
diff --git a/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc b/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc
index a570b374231..2a0676b72ff 100644
--- a/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc
+++ b/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc
@@ -181,7 +181,7 @@ void MeshFromGeometry::create_polys_loops(Mesh *mesh, bool use_vertex_groups)
   const int64_t total_verts = mesh_geometry_.get_vertex_count();
   if (use_vertex_groups && total_verts && mesh_geometry_.has_vertex_groups_) {
     mesh->dvert = static_cast<MDeformVert *>(
-        CustomData_add_layer(&mesh->vdata, CD_MDEFORMVERT, CD_CALLOC, nullptr, total_verts));
+        CustomData_add_layer(&mesh->vdata, CD_MDEFORMVERT, CD_SET_DEFAULT, nullptr, total_verts));
   }
 
   const int64_t tot_face_elems{mesh->totpoly};
@@ -262,7 +262,7 @@ void MeshFromGeometry::create_uv_verts(Mesh *mesh)
     return;
   }
   MLoopUV *mluv_dst = static_cast<MLoopUV *>(CustomData_add_layer(
-      &mesh->ldata, CD_MLOOPUV, CD_DEFAULT, nullptr, mesh_geometry_.total_loops_));
+      &mesh->ldata, CD_MLOOPUV, CD_SET_DEFAULT, nullptr, mesh_geometry_.total_loops_));
   int tot_loop_idx = 0;
 
   for (const PolyElem &curr_face : mesh_geometry_.face_elements_) {
diff --git a/source/blender/io/wavefront_obj/tests/obj_importer_tests.cc b/source/blender/io/wavefront_obj/tests/obj_importer_tests.cc
index bd9360548af..35f977f41df 100644
--- a/source/blender/io/wavefront_obj/tests/obj_importer_tests.cc
+++ b/source/blender/io/wavefront_obj/tests/obj_importer_tests.cc
@@ -12,7 +12,7 @@
 #include "BKE_scene.h"
 
 #include "BLI_listbase.h"
-#include "BLI_math_base.h"
+#include "BLI_math_base.hh"
 #include "BLI_math_vec_types.hh"
 
 #include "BLO_readfile.h"