Alembic: support reading per-vertex UV sets

This adds support for importing UV sets which are defined per vertex,
instead of per face corners. Such UV sets can be generated when the
mesh is split according to UV islands, or when there is only one UV
island, in which cases only a single UV value can be stored per
vertex since vertices will never be on a seam.

Reviewed By: sybren

Differential Revision: https://developer.blender.org/D11584

1 files changed, 25 insertions, 16 deletions

diff --git a/source/blender/io/alembic/intern/abc_reader_mesh.cc b/source/blender/io/alembic/intern/abc_reader_mesh.cc
index 11b6c1c18ca..79f34f671c7 100644
--- a/source/blender/io/alembic/intern/abc_reader_mesh.cc
+++ b/source/blender/io/alembic/intern/abc_reader_mesh.cc
@@ -121,6 +121,7 @@ struct AbcMeshData {
   P3fArraySamplePtr positions;
   P3fArraySamplePtr ceil_positions;
 
+  AbcUvScope uv_scope;
   V2fArraySamplePtr uvs;
   UInt32ArraySamplePtr uvs_indices;
 };
@@ -192,8 +193,9 @@ static void read_mpolys(CDStreamConfig &config, const AbcMeshData &mesh_data)
 
   const UInt32ArraySamplePtr &uvs_indices = mesh_data.uvs_indices;
 
-  const bool do_uvs = (mloopuvs && uvs && uvs_indices) &&
-                      (uvs_indices->size() == face_indices->size());
+  const bool do_uvs = (mloopuvs && uvs && uvs_indices);
+  const bool do_uvs_per_loop = do_uvs && mesh_data.uv_scope == ABC_UV_SCOPE_LOOP;
+  BLI_assert(!do_uvs || mesh_data.uv_scope != ABC_UV_SCOPE_NONE);
   unsigned int loop_index = 0;
   unsigned int rev_loop_index = 0;
   unsigned int uv_index = 0;
@@ -227,8 +229,7 @@ static void read_mpolys(CDStreamConfig &config, const AbcMeshData &mesh_data)
 
       if (do_uvs) {
         MLoopUV &loopuv = mloopuvs[rev_loop_index];
-
-        uv_index = (*uvs_indices)[loop_index];
+        uv_index = (*uvs_indices)[do_uvs_per_loop ? loop_index : loop.v];
 
         /* Some Alembic files are broken (or at least export UVs in a way we don't expect). */
         if (uv_index >= uvs_size) {
@@ -357,22 +358,29 @@ BLI_INLINE void read_uvs_params(CDStreamConfig &config,
   IV2fGeomParam::Sample uvsamp;
   uv.getIndexed(uvsamp, selector);
 
-  abc_data.uvs = uvsamp.getVals();
-  abc_data.uvs_indices = uvsamp.getIndices();
+  UInt32ArraySamplePtr uvs_indices = uvsamp.getIndices();
 
-  if (abc_data.uvs_indices->size() == config.totloop) {
-    std::string name = Alembic::Abc::GetSourceName(uv.getMetaData());
+  const AbcUvScope uv_scope = get_uv_scope(uv.getScope(), config, uvs_indices);
 
-    /* According to the convention, primary UVs should have had their name
-     * set using Alembic::Abc::SetSourceName, but you can't expect everyone
-     * to follow it! :) */
-    if (name.empty()) {
-      name = uv.getName();
-    }
+  if (uv_scope == ABC_UV_SCOPE_NONE) {
+    return;
+  }
 
-    void *cd_ptr = config.add_customdata_cb(config.mesh, name.c_str(), CD_MLOOPUV);
-    config.mloopuv = static_cast<MLoopUV *>(cd_ptr);
+  abc_data.uv_scope = uv_scope;
+  abc_data.uvs = uvsamp.getVals();
+  abc_data.uvs_indices = uvs_indices;
+
+  std::string name = Alembic::Abc::GetSourceName(uv.getMetaData());
+
+  /* According to the convention, primary UVs should have had their name
+   * set using Alembic::Abc::SetSourceName, but you can't expect everyone
+   * to follow it! :) */
+  if (name.empty()) {
+    name = uv.getName();
   }
+
+  void *cd_ptr = config.add_customdata_cb(config.mesh, name.c_str(), CD_MLOOPUV);
+  config.mloopuv = static_cast<MLoopUV *>(cd_ptr);
 }
 
 static void *add_customdata_cb(Mesh *mesh, const char *name, int data_type)
@@ -462,6 +470,7 @@ CDStreamConfig get_config(Mesh *mesh, const bool use_vertex_interpolation)
   config.mvert = mesh->mvert;
   config.mloop = mesh->mloop;
   config.mpoly = mesh->mpoly;
+  config.totvert = mesh->totvert;
   config.totloop = mesh->totloop;
   config.totpoly = mesh->totpoly;
   config.loopdata = &mesh->ldata;