Attribute Node: access geometry node instance attributes.

The Instancer mode of the node is intended for varying material
behavior between instances. Since Geometry Nodes support arbitrary
named instance attributes, this mode should include them in lookup.

To implement this it is sufficient to store references to Geometry
Node data in DupliObject, and check it during dupli attribute lookup.

In order to reduce the memory usage of DupliObject, only 4 array
entries are allocated, even though the current dupli recursion stack
limit is 8. This assumes that not every entry would be associated with
a GeometrySet instance. Hopefully, soon the whole system will be
rewritten to remove the hard limits altogether.

Differential Revision: https://developer.blender.org/D16114

1 files changed, 11 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_duplilist.h b/source/blender/blenkernel/BKE_duplilist.h
index 79f37d2edde..8a37348377a 100644
--- a/source/blender/blenkernel/BKE_duplilist.h
+++ b/source/blender/blenkernel/BKE_duplilist.h
@@ -60,6 +60,17 @@ typedef struct DupliObject {
   /* Particle this dupli was generated from. */
   struct ParticleSystem *particle_system;
 
+  /* Geometry set stack for instance attributes; for each level lists the
+   * geometry set and instance index within it.
+   *
+   * Only non-null entries are stored, ordered from innermost to outermost.
+   * To save memory, these arrays are allocated smaller than persistent_id,
+   * assuming that not every entry will be associated with a GeometrySet; any
+   * size between 1 and MAX_DUPLI_RECUR can be used without issues.
+   */
+  int instance_idx[4];
+  const struct GeometrySet *instance_data[4];
+
   /* Random ID for shading */
   unsigned int random_id;
 } DupliObject;