source/blender/blenkernel/BKE_simulation_state.hh

@@ -18,23 +18,15 @@ class SimulationStateItem {
 };
 
 class GeometrySimulationStateItem : public SimulationStateItem {
- private:
-  GeometrySet geometry_;
-
  public:
-  GeometrySimulationStateItem(GeometrySet geometry);
-
-  const GeometrySet &geometry() const
-  {
-    return geometry_;
-  }
-
-  GeometrySet &geometry()
-  {
-    return geometry_;
-  }
+  GeometrySet geometry;
 };
 
+/**
+ * References a field input/output that becomes an attribute as part of the simulation state.
+ * The attribute is actually stored in a #GeometrySimulationStateItem, so this just references
+ * the attribute's name.
+ */
 class AttributeSimulationStateItem : public SimulationStateItem {
  private:
   std::string name_;
@@ -48,6 +40,7 @@ class AttributeSimulationStateItem : public SimulationStateItem {
   }
 };
 
+/** Storage for a single value of a trivial type like `float`, `int`, etc. */
 class PrimitiveSimulationStateItem : public SimulationStateItem {
  private:
   const CPPType &type_;
@@ -81,12 +74,19 @@ class StringSimulationStateItem : public SimulationStateItem {
   }
 };
 
+/**
+ * Storage of values for a single simulation input and output node pair.
+ * Used as a cache to allow random access in time, and as an intermediate form before data is
+ * baked.
+ */
 class SimulationZoneState {
  public:
   Map<int, std::unique_ptr<SimulationStateItem>> item_by_identifier;
 };
 
+/** Identifies a simulation zone (input and output node pair) used by a modifier. */
 struct SimulationZoneID {
+  /** Every node identifier in the hierarchy of compute contexts. */
   Vector<int> node_ids;
 
   uint64_t hash() const
@@ -100,6 +100,10 @@ struct SimulationZoneID {
   }
 };
 
+/**
+ * Stores a single frame of simulation states for all simulation zones in a modifier's node
+ * hierarchy.
+ */
 class ModifierSimulationState {
  private:
   mutable bool bake_loaded_;
@@ -108,7 +112,9 @@ class ModifierSimulationState {
   ModifierSimulationCache *owner_;
   mutable std::mutex mutex_;
   Map<SimulationZoneID, std::unique_ptr<SimulationZoneState>> zone_states_;
+  /** File path to folder containing baked meta-data. */
   std::optional<std::string> meta_path_;
+  /** File path to folder containing baked data. */
   std::optional<std::string> bdata_dir_;
 
   const SimulationZoneState *get_zone_state(const SimulationZoneID &zone_id) const;
@@ -122,8 +128,14 @@ struct ModifierSimulationStateAtFrame {
 };
 
 enum class CacheState {
+  /** The cache is up-to-date with the inputs. */
   Valid,
+  /**
+   * Nodes or input values have changed since the cache was created, i.e. the output would be
+   * different if the simulation was run again.
+   */
   Invalid,
+  /** The cache has been baked and will not be invalidated by changing inputs. */
   Baked,
 };
 
@@ -136,6 +148,10 @@ struct StatesAroundFrame {
 class ModifierSimulationCache {
  private:
   Vector<std::unique_ptr<ModifierSimulationStateAtFrame>> states_at_frames_;
+  /**
+   * Used for baking to deduplicate arrays when writing and writing from storage. Sharing info
+   * must be kept alive for multiple frames to detect if each data array's version has changed.
+   */
   std::unique_ptr<BDataSharing> bdata_sharing_;
 
   friend ModifierSimulationState;

source/blender/blenkernel/intern/simulation_state.cc

@@ -15,11 +15,6 @@
 
 namespace blender::bke::sim {
 
-GeometrySimulationStateItem::GeometrySimulationStateItem(GeometrySet geometry)
-    : geometry_(std::move(geometry))
-{
-}
-
 PrimitiveSimulationStateItem::PrimitiveSimulationStateItem(const CPPType &type, const void *value)
     : type_(type)
 {

source/blender/blenkernel/intern/simulation_state_serialize.cc

@@ -835,8 +835,7 @@ void serialize_modifier_simulation_state(const ModifierSimulationState &state,
       {
         io_state_item->append_str("type", "GEOMETRY");
 
-        const GeometrySet &geometry = geometry_state_item->geometry();
-
+        const GeometrySet &geometry = geometry_state_item->geometry;
         auto io_geometry = serialize_geometry_set(geometry, bdata_writer, bdata_sharing);
         io_state_item->append("data", io_geometry);
       }

source/blender/nodes/geometry/nodes/node_geo_simulation_output.cc

@@ -181,7 +181,7 @@ void simulation_state_to_values(const Span<NodeSimulationItem> node_simulation_i
         if (const auto *geo_state_item =
                 dynamic_cast<const bke::sim::GeometrySimulationStateItem *>(&state_item))
         {
-          GeometrySet *geometry = new (r_output_value) GeometrySet(geo_state_item->geometry());
+          GeometrySet *geometry = new (r_output_value) GeometrySet(geo_state_item->geometry);
           geometries.append(geometry);
         }
         else {
@@ -282,7 +282,7 @@ void values_to_simulation_state(const Span<NodeSimulationItem> node_simulation_i
         GeometrySet &geometry = *static_cast<GeometrySet *>(input_value);
         auto geometry_state_item = std::make_unique<bke::sim::GeometrySimulationStateItem>(
             std::move(geometry));
-        stored_geometries.append(&geometry_state_item->geometry());
+        stored_geometries.append(&geometry_state_item->geometry);
         state_item = std::move(geometry_state_item);
         break;
       }