Geometry Nodes: Experimental rigid body integration.

This is an exploration of how geometry nodes might be coupled with
rigid bodies and iterative simulations in general. It's a very
rough-and-ready implementation, not meant as a final version, but rather
to prove the possiblity and to find challenging areas where redesign is
needed.

The core additions are:
- Geometry nodes to flag points and/or instances as rigid bodies.
- Depsgraph integration to ensure the necessary order of operations
    between modifiers and rigid body pre/post simulation updates.
- Simple cache feature to store arbitrary geometry and loop back into
    the next iteration.

1 files changed, 3 insertions, 3 deletions

diff --git a/source/blender/editors/space_node/node_add.cc b/source/blender/editors/space_node/node_add.cc
index 975d4eda7e3..715b7c80d1d 100644
--- a/source/blender/editors/space_node/node_add.cc
+++ b/source/blender/editors/space_node/node_add.cc
@@ -490,7 +490,7 @@ static int node_add_object_invoke(bContext *C, wmOperator *op, const wmEvent *ev
 static bool node_add_object_poll(bContext *C)
 {
   const SpaceNode *snode = CTX_wm_space_node(C);
-  return ED_operator_node_editable(C) && ELEM(snode->nodetree->type, NTREE_GEOMETRY) &&
+  return ED_operator_node_editable(C) && ELEM(snode->nodetree->type, NTREE_GEOMETRY, NTREE_SIMULATION) &&
          !UI_but_active_drop_name(C);
 }
 
@@ -578,7 +578,7 @@ static int node_add_collection_invoke(bContext *C, wmOperator *op, const wmEvent
 static bool node_add_collection_poll(bContext *C)
 {
   const SpaceNode *snode = CTX_wm_space_node(C);
-  return ED_operator_node_editable(C) && ELEM(snode->nodetree->type, NTREE_GEOMETRY) &&
+  return ED_operator_node_editable(C) && ELEM(snode->nodetree->type, NTREE_GEOMETRY, NTREE_SIMULATION) &&
          !UI_but_active_drop_name(C);
 }
 
@@ -610,7 +610,7 @@ static bool node_add_file_poll(bContext *C)
 {
   const SpaceNode *snode = CTX_wm_space_node(C);
   return ED_operator_node_editable(C) &&
-         ELEM(snode->nodetree->type, NTREE_SHADER, NTREE_TEXTURE, NTREE_COMPOSIT, NTREE_GEOMETRY);
+         ELEM(snode->nodetree->type, NTREE_SHADER, NTREE_TEXTURE, NTREE_COMPOSIT, NTREE_GEOMETRY, NTREE_SIMULATION);
 }
 
 static int node_add_file_exec(bContext *C, wmOperator *op)