Geometry Nodes: Make simulation caching optional

For realtime use cases, storing the geometry's state in memory at every
frame can be prohibitively expensive. This commit adds an option to
disable the caching, stored per object and accessible in the baking
panel. The default is still to enable caching.

Pull Request: https://projects.blender.org/blender/blender/pulls/107767

scripts/startup/bl_ui/properties_physics_geometry_nodes.py

@@ -39,6 +39,11 @@ class PHYSICS_PT_geometry_nodes(Panel):
         row.operator("object.simulation_nodes_cache_bake", text=bake_text).selected = True
         row.operator("object.simulation_nodes_cache_delete", text="", icon='TRASH').selected = True
 
+        layout.use_property_split = True
+        layout.use_property_decorate = False
+        ob = context.object
+        layout.prop(ob, "use_simulation_cache", text="Cache")
+
 
 classes = (
     PHYSICS_PT_geometry_nodes,

source/blender/blenkernel/BKE_blender_version.h

@@ -31,7 +31,7 @@ extern "C" {
  * version. Older Blender versions will test this and show a warning if the file
  * was written with too new a version. */
 #define BLENDER_FILE_MIN_VERSION 305
-#define BLENDER_FILE_MIN_SUBVERSION 8
+#define BLENDER_FILE_MIN_SUBVERSION 9
 
 /** User readable version string. */
 const char *BKE_blender_version_string(void);

source/blender/blenkernel/BKE_simulation_state.hh

@@ -181,6 +181,7 @@ class ModifierSimulationCache {
   }
 
   void reset();
+  void clear_prev_states();
 };
 
 }  // namespace blender::bke::sim

source/blender/blenkernel/intern/simulation_state.cc

@@ -202,6 +202,15 @@ void ModifierSimulationState::ensure_bake_loaded() const
   bake_loaded_ = true;
 }
 
+void ModifierSimulationCache::clear_prev_states()
+{
+  std::lock_guard lock(states_at_frames_mutex_);
+  std::unique_ptr<ModifierSimulationStateAtFrame> temp = std::move(states_at_frames_.last());
+  states_at_frames_.clear_and_shrink();
+  bdata_sharing_.reset();
+  states_at_frames_.append(std::move(temp));
+}
+
 void ModifierSimulationCache::reset()
 {
   std::lock_guard lock(states_at_frames_mutex_);

source/blender/blenloader/intern/versioning_280.c

@@ -3472,7 +3472,7 @@ void blo_do_versions_280(FileData *fd, Library *UNUSED(lib), Main *bmain)
     }
 
     for (Object *ob = bmain->objects.first; ob; ob = ob->id.next) {
-      ob->flag &= ~(OB_FLAG_UNUSED_11 | OB_FLAG_UNUSED_12);
+      ob->flag &= ~(OB_FLAG_USE_SIMULATION_CACHE | OB_FLAG_UNUSED_12);
       ob->transflag &= ~(OB_TRANSFORM_ADJUST_ROOT_PARENT_FOR_VIEW_LOCK | OB_TRANSFLAG_UNUSED_1);
       ob->shapeflag &= ~OB_SHAPE_FLAG_UNUSED_1;
     }

source/blender/blenloader/intern/versioning_300.cc

@@ -4351,6 +4351,13 @@ void blo_do_versions_300(FileData *fd, Library * /*lib*/, Main *bmain)
       }
     }
   }
+
+  if (!MAIN_VERSION_ATLEAST(bmain, 306, 8)) {
+    LISTBASE_FOREACH (Object *, ob, &bmain->objects) {
+      ob->flag |= OB_FLAG_USE_SIMULATION_CACHE;
+    }
+  }
+
   /**
    * Versioning code until next subversion bump goes here.
    *

source/blender/makesdna/DNA_object_defaults.h

@@ -37,6 +37,7 @@
     .drotAngle = 0, \
     .quat = _DNA_DEFAULT_UNIT_QT, \
     .dquat = _DNA_DEFAULT_UNIT_QT, \
+    .flag = OB_FLAG_USE_SIMULATION_CACHE, \
     .protectflag = OB_LOCK_ROT4D, \
  \
     .dt = OB_TEXTURE, \

source/blender/makesdna/DNA_object_types.h

@@ -720,8 +720,8 @@ enum {
 
 #define OB_FROMDUPLI (1 << 9)
 #define OB_DONE (1 << 10) /* unknown state, clear before use */
+#define OB_FLAG_USE_SIMULATION_CACHE (1 << 11)
 #ifdef DNA_DEPRECATED_ALLOW
-#  define OB_FLAG_UNUSED_11 (1 << 11) /* cleared */
 #  define OB_FLAG_UNUSED_12 (1 << 12) /* cleared */
 #endif
 

source/blender/makesrna/intern/rna_object.c

@@ -3679,6 +3679,12 @@ static void rna_def_object(BlenderRNA *brna)
   RNA_def_property_struct_type(prop, "RigidBodyConstraint");
   RNA_def_property_ui_text(prop, "Rigid Body Constraint", "Constraint constraining rigid bodies");
 
+  prop = RNA_def_property(srna, "use_simulation_cache", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "flag", OB_FLAG_USE_SIMULATION_CACHE);
+  RNA_def_property_ui_text(
+      prop, "Use Simulation Cache", "Cache all frames during simulation nodes playback");
+  RNA_def_property_update(prop, NC_OBJECT | ND_DRAW, NULL);
+
   rna_def_object_visibility(srna);
 
   /* instancing */

source/blender/modifiers/intern/MOD_nodes.cc

@@ -1351,6 +1351,14 @@ static GeometrySet compute_geometry(const bNodeTree &btree,
     nmd_orig->runtime_eval_log = eval_log.release();
   }
 
+  if (DEG_is_active(ctx->depsgraph)) {
+    /* When caching is turned off, remove all states except the last which was just created in this
+     * evaluation. Check if active status to avoid changing original data in other depsgraphs. */
+    if (!(ctx->object->flag & OB_FLAG_USE_SIMULATION_CACHE)) {
+      nmd_orig->simulation_cache->clear_prev_states();
+    }
+  }
+
   return output_geometry_set;
 }