Geometry Nodes: Run nodes once on unique instance data

As described in T91672, often it can be much more efficient to run each
node only on the unique geometry of the instances, rather than realizing
all instances and potentially processing redundant data. Sometimes the
performance difference can be completely smooth vs. completely unusable.

Geometry nodes used to hide that choice from users by always realizing
instances, but recently we have decided to expose it. So this commit
makes nodes run once per unique reference in the entire tree of nested
instances in their input geometries, continuing the work started in
rB0559971ab377 and rBf94164d89629f0d2. For the old behavior, a realize
instances node can be added before the nodes, which is done in the
versioning code.

Differential Revision: https://developer.blender.org/D12656

3 files changed, 12 insertions, 1 deletions

diff --git a/source/blender/blenkernel/BKE_blender_version.h b/source/blender/blenkernel/BKE_blender_version.h
index b973d8b9a18..5ef0459663b 100644
--- a/source/blender/blenkernel/BKE_blender_version.h
+++ b/source/blender/blenkernel/BKE_blender_version.h
@@ -39,7 +39,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 27
+#define BLENDER_FILE_SUBVERSION 28
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and show a warning if the file
diff --git a/source/blender/blenkernel/BKE_geometry_set.hh b/source/blender/blenkernel/BKE_geometry_set.hh
index 4954b1d5ab2..724ca224cab 100644
--- a/source/blender/blenkernel/BKE_geometry_set.hh
+++ b/source/blender/blenkernel/BKE_geometry_set.hh
@@ -330,6 +330,7 @@ struct GeometrySet {
   bool has_volume() const;
   bool has_curve() const;
   bool has_realized_data() const;
+  bool is_empty() const;
 
   const Mesh *get_mesh_for_read() const;
   const PointCloud *get_pointcloud_for_read() const;
diff --git a/source/blender/blenkernel/intern/geometry_set.cc b/source/blender/blenkernel/intern/geometry_set.cc
index 400e0fda518..0aac6ae3adf 100644
--- a/source/blender/blenkernel/intern/geometry_set.cc
+++ b/source/blender/blenkernel/intern/geometry_set.cc
@@ -318,6 +318,16 @@ bool GeometrySet::has_realized_data() const
   return this->get_component_for_read<InstancesComponent>() == nullptr;
 }
 
+/* Return true if the geometry set has any component that isn't empty. */
+bool GeometrySet::is_empty() const
+{
+  if (components_.is_empty()) {
+    return true;
+  }
+  return !(this->has_mesh() || this->has_curve() || this->has_pointcloud() ||
+           this->has_instances());
+}
+
 /* Create a new geometry set that only contains the given mesh. */
 GeometrySet GeometrySet::create_with_mesh(Mesh *mesh, GeometryOwnershipType ownership)
 {