Bugfix [#33970] Background Scene does not show animation of rigid body objects

This was caused by multiple instantiations of the same basic problem. The
rigidbody handling code often assumed that "scene" pointers referred to the
scene where an object participating in the sim resided (and where the rigidbody
world for that sim lived). However, when dealing with background sets, "scene"
often only refers to the active scene, and not the set that the object actually
came from. Hence, the rigidbody code would often (wrongly) conclude that there
was nothing to do.

For example, we may have the following backgound set/scene chaining scenario:
"active"  <-- ... <-- set i (rigidbody objects live here) <-- ... <-- set n

The fix here is a multi-part fix:
1) Moved sim-world calculation from BKE_scene_update_newframe() to
scene_update_tagged_recursive()
    + This is currently the only way that rigidbody sims in background sets will
get calculated, as part of the recursion
     - These checks will get run on each update. <--- FIXME!!!

2) Tweaked depsgraph code so that when checking if there are any time-dependent
features on objects to tag for updating, the checking is done relative to the
scene that the object actually resides in (and not the active scene). Otherwise,
even if we recalculate the sim, the affected objects won't get tagged for
updating. This tagging is needed to actually flush the transforms out of the
RigidBodyObject structs (written by the sim/cache) and into the Object
transforms (obmat's)

3) Removed the requirement for rigidbody world to actually exist before we can
flush rigidbody transforms. In many cases, it should be sufficient to assume
that because the object with rigidbody data attached has been tagged for
updates, it should have updates to perform. Of course, we still check on this
data if we've got it, but that's only if the sim is in the active scene.
   - TODO: if we have further problems, we should investigate passing the
"actual" scene down alongside the "active" scene for BKE_object_handle_update().

1 files changed, 18 insertions, 8 deletions

diff --git a/source/blender/blenkernel/intern/scene.c b/source/blender/blenkernel/intern/scene.c
index 30550edc007..13e050f12b7 100644
--- a/source/blender/blenkernel/intern/scene.c
+++ b/source/blender/blenkernel/intern/scene.c
@@ -1093,7 +1093,6 @@ static void scene_update_tagged_recursive(Main *bmain, Scene *scene, Scene *scen
 {
 	Base *base;
 	
-	
 	scene->customdata_mask = scene_parent->customdata_mask;
 
 	/* sets first, we allow per definition current scene to have
@@ -1101,6 +1100,23 @@ static void scene_update_tagged_recursive(Main *bmain, Scene *scene, Scene *scen
 	if (scene->set)
 		scene_update_tagged_recursive(bmain, scene->set, scene_parent);
 	
+	/* run rigidbody sim 
+	 * - calculate/read values from cache into RBO's, to get flushed 
+	 *   later when objects are evaluated (if they're tagged for eval)
+	 */
+	// XXX: this position may still change, objects not being updated correctly before simulation is run
+	// NOTE: current position is so that rigidbody sim affects other objects
+	// FIXME: this now gets executed on every update, not just frame change now!!!
+	if (BKE_scene_check_rigidbody_active(scene)) {
+		/* we use frame time of parent (this is "scene" itself for top-level of sets recursion), 
+		 * as that is the active scene controlling all timing in file at the moment
+		 */
+		float ctime = BKE_scene_frame_get(scene_parent);
+		
+		/* however, "scene" contains the rigidbody world needed for eval... */
+		BKE_rigidbody_do_simulation(scene, ctime);
+	}
+	
 	/* scene objects */
 	for (base = scene->base.first; base; base = base->next) {
 		Object *ob = base->object;
@@ -1206,13 +1222,7 @@ void BKE_scene_update_for_newframe(Main *bmain, Scene *sce, unsigned int lay)
 	 * such as Scene->World->MTex/Texture) can still get correctly overridden.
 	 */
 	BKE_animsys_evaluate_all_animation(bmain, sce, ctime);
-	/*...done with recusrive funcs */
-
-	/* run rigidbody sim */
-	// XXX: this position may still change, objects not being updated correctly before simulation is run
-	// NOTE: current position is so that rigidbody sim affects other objects
-	if (BKE_scene_check_rigidbody_active(sce))
-		BKE_rigidbody_do_simulation(sce, ctime);
+	/*...done with recursive funcs */
 
 	/* clear "LIB_DOIT" flag from all materials, to prevent infinite recursion problems later 
 	 * when trying to find materials with drivers that need evaluating [#32017]