Alembic Procedural: only subdivide if subsurf modifier is present

As subdivision objects are first class citizens in Alembic, to
differentiate them with non-subdivided polygon meshes, the Alembic
Procedural automatically sets up subdivision properties on the generated
Cycles Mesh.

However, for real-time playback subdivision is far too slow, so this
modifies the detection of a MeshSeqCache modifier used to activate the
procedural to allow for a Subsurf modifier right after the cache one. If
present, the procedural will tag the object for subdivision, if absent, the
object will be treated as a regular mesh.

This is a temporary measure for until subdivision surface settings are part
of the Mesh datablock (see T68891).

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D11162

1 files changed, 11 insertions, 1 deletions

diff --git a/intern/cycles/blender/blender_util.h b/intern/cycles/blender/blender_util.h
index e50b1a4760e..3cf75b338dc 100644
--- a/intern/cycles/blender/blender_util.h
+++ b/intern/cycles/blender/blender_util.h
@@ -573,7 +573,8 @@ static inline BL::FluidDomainSettings object_fluid_gas_domain_find(BL::Object &b
 }
 
 static inline BL::MeshSequenceCacheModifier object_mesh_cache_find(BL::Object &b_ob,
-                                                                   bool check_velocity)
+                                                                   bool check_velocity,
+                                                                   bool *has_subdivision_modifier)
 {
   for (int i = b_ob.modifiers.length() - 1; i >= 0; --i) {
     BL::Modifier b_mod = b_ob.modifiers[i];
@@ -595,6 +596,15 @@ static inline BL::MeshSequenceCacheModifier object_mesh_cache_find(BL::Object &b
       continue;
     }
 
+    /* Only skip the subsurf modifier if we are not checking for the mesh sequence cache modifier
+     * for motion blur. */
+    if (b_mod.type() == BL::Modifier::type_SUBSURF && !check_velocity) {
+      if (has_subdivision_modifier) {
+        *has_subdivision_modifier = true;
+      }
+      continue;
+    }
+
     break;
   }