Alembic: read/write generated coordinates of meshes

Read and write generated coordinates (also known as "original
coordinates", "reference coordinates", or "orcos") from and to Alembic.
A custom geometry property named "Pref" is used for (hopefully)
interoperability with Maya and Houdini. For now it's only guaranteed for
Blender-to-Blender.

Export: writing generated coordinates is optional (on by default).

Import: generated coordinates are always read whenever the reading of
vertex data is enabled.

Manifest Task: T88081

1 files changed, 9 insertions, 0 deletions

diff --git a/source/blender/io/alembic/exporter/abc_writer_mesh.cc b/source/blender/io/alembic/exporter/abc_writer_mesh.cc
index 29b29324ee3..fd7db005dd2 100644
--- a/source/blender/io/alembic/exporter/abc_writer_mesh.cc
+++ b/source/blender/io/alembic/exporter/abc_writer_mesh.cc
@@ -200,6 +200,7 @@ void ABCGenericMeshWriter::do_write(HierarchyContext &context)
   }
 
   m_custom_data_config.pack_uvs = args_.export_params->packuv;
+  m_custom_data_config.mesh = mesh;
   m_custom_data_config.mpoly = mesh->mpoly;
   m_custom_data_config.mloop = mesh->mloop;
   m_custom_data_config.totpoly = mesh->totpoly;
@@ -279,6 +280,10 @@ void ABCGenericMeshWriter::write_mesh(HierarchyContext &context, Mesh *mesh)
     mesh_sample.setNormals(normals_sample);
   }
 
+  if (args_.export_params->orcos) {
+    write_generated_coordinates(abc_poly_mesh_schema_.getArbGeomParams(), m_custom_data_config);
+  }
+
   if (liquid_sim_modifier_ != nullptr) {
     get_velocities(mesh, velocities);
     mesh_sample.setVelocities(V3fArraySample(velocities));
@@ -329,6 +334,10 @@ void ABCGenericMeshWriter::write_subd(HierarchyContext &context, struct Mesh *me
         abc_subdiv_schema_.getArbGeomParams(), m_custom_data_config, &mesh->ldata, CD_MLOOPUV);
   }
 
+  if (args_.export_params->orcos) {
+    write_generated_coordinates(abc_poly_mesh_schema_.getArbGeomParams(), m_custom_data_config);
+  }
+
   if (!crease_indices.empty()) {
     subdiv_sample.setCreaseIndices(Int32ArraySample(crease_indices));
     subdiv_sample.setCreaseLengths(Int32ArraySample(crease_lengths));