Modifiers: export motion blur velocity through attribute

Previously fluid simulation and Alembic modifiers had a dedicated function
to query the velocity for motion blur. Now use a more generic system where
those modifiers output a velocity attribute.

Advantages:
* Geometry and particle nodes can output velocity through the same mechanism,
  or read the attribute coming from earlier modifiers.
* The velocity can be preserved through modifiers like subdivision surface or
  auto smooth.
* USD and Alembic previously only output velocity from fluid simulation, now
  they work with velocity from other sources too.
* Simplifies the code for renderers like Cycles and exporters like
  Alembic and USD.

This breaks compatibility:
* External renderers and exporters accessing these velocities through the
  Python API now need to use the attribute instead.
* Existing modifier node setups that create an attribute named "velocity"
  will render differently with motion blur.

Differential Revision: https://developer.blender.org/D12305

1 files changed, 0 insertions, 81 deletions

diff --git a/source/blender/makesrna/intern/rna_modifier.c b/source/blender/makesrna/intern/rna_modifier.c
index fb4fd4528d6..c99dfea524f 100644
--- a/source/blender/makesrna/intern/rna_modifier.c
+++ b/source/blender/makesrna/intern/rna_modifier.c
@@ -1601,51 +1601,6 @@ static bool rna_Modifier_show_expanded_get(PointerRNA *ptr)
   return md->ui_expand_flag & UI_PANEL_DATA_EXPAND_ROOT;
 }
 
-static int rna_MeshSequenceCacheModifier_has_velocity_get(PointerRNA *ptr)
-{
-#  ifdef WITH_ALEMBIC
-  MeshSeqCacheModifierData *mcmd = (MeshSeqCacheModifierData *)ptr->data;
-  return ABC_has_vec3_array_property_named(mcmd->reader, mcmd->cache_file->velocity_name);
-#  else
-  return false;
-  UNUSED_VARS(ptr);
-#  endif
-}
-
-static int rna_MeshSequenceCacheModifier_read_velocity_get(PointerRNA *ptr)
-{
-#  ifdef WITH_ALEMBIC
-  MeshSeqCacheModifierData *mcmd = (MeshSeqCacheModifierData *)ptr->data;
-
-  if (mcmd->num_vertices == 0) {
-    return 0;
-  }
-
-  if (mcmd->vertex_velocities) {
-    MEM_freeN(mcmd->vertex_velocities);
-  }
-
-  mcmd->vertex_velocities = MEM_mallocN(sizeof(MeshCacheVertexVelocity) * mcmd->num_vertices,
-                                        "Mesh Cache Velocities");
-
-  int num_read = ABC_read_velocity_cache(mcmd->reader,
-                                         mcmd->cache_file->velocity_name,
-                                         mcmd->last_lookup_time,
-                                         mcmd->velocity_scale * mcmd->velocity_delta,
-                                         mcmd->num_vertices,
-                                         (float *)mcmd->vertex_velocities);
-
-  if (num_read == -1 || num_read != mcmd->num_vertices) {
-    return false;
-  }
-
-  return true;
-#  else
-  return false;
-  UNUSED_VARS(ptr);
-#  endif
-}
-
 static bool rna_NodesModifier_node_group_poll(PointerRNA *UNUSED(ptr), PointerRNA value)
 {
   bNodeTree *ntree = value.data;
@@ -6118,22 +6073,6 @@ static void rna_def_modifier_meshcache(BlenderRNA *brna)
   RNA_define_lib_overridable(false);
 }
 
-static void rna_def_mesh_cache_velocities(BlenderRNA *brna)
-{
-  StructRNA *srna;
-  PropertyRNA *prop;
-
-  srna = RNA_def_struct(brna, "MeshCacheVertexVelocity", NULL);
-  RNA_def_struct_ui_text(srna, "Mesh Cache Velocity", "Velocity attribute of an Alembic mesh");
-  RNA_def_struct_ui_icon(srna, ICON_VERTEXSEL);
-
-  prop = RNA_def_property(srna, "velocity", PROP_FLOAT, PROP_VELOCITY);
-  RNA_def_property_array(prop, 3);
-  RNA_def_property_float_sdna(prop, NULL, "vel");
-  RNA_def_property_ui_text(prop, "Velocity", "");
-  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
-}
-
 static void rna_def_modifier_meshseqcache(BlenderRNA *brna)
 {
   StructRNA *srna;
@@ -6190,26 +6129,6 @@ static void rna_def_modifier_meshseqcache(BlenderRNA *brna)
       "Multiplier used to control the magnitude of the velocity vectors for time effects");
   RNA_def_property_update(prop, 0, "rna_Modifier_update");
 
-  /* -------------------------- Velocity Vectors -------------------------- */
-
-  prop = RNA_def_property(srna, "vertex_velocities", PROP_COLLECTION, PROP_NONE);
-  RNA_def_property_collection_sdna(prop, NULL, "vertex_velocities", "num_vertices");
-  RNA_def_property_struct_type(prop, "MeshCacheVertexVelocity");
-  RNA_def_property_ui_text(
-      prop, "Fluid Mesh Vertices", "Vertices of the fluid mesh generated by simulation");
-
-  rna_def_mesh_cache_velocities(brna);
-
-  prop = RNA_def_property(srna, "has_velocity", PROP_BOOLEAN, PROP_NONE);
-  RNA_def_property_ui_text(prop, "Has Velocity Cache", "");
-  RNA_def_property_boolean_funcs(prop, "rna_MeshSequenceCacheModifier_has_velocity_get", NULL);
-  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
-
-  prop = RNA_def_property(srna, "read_velocity", PROP_BOOLEAN, PROP_NONE);
-  RNA_def_property_ui_text(prop, "Read Velocity Cache", "");
-  RNA_def_property_boolean_funcs(prop, "rna_MeshSequenceCacheModifier_read_velocity_get", NULL);
-  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
-
   RNA_define_lib_overridable(false);
 }