From d0c1e6df08b3d202291fc60f042990d3aeb75ee3 Mon Sep 17 00:00:00 2001
From: Hans Goudey <h.goudey@me.com>
Date: Tue, 9 May 2023 13:53:16 -0400
Subject: [PATCH] Cleanup: Avoid state creation for first simulation input node
 evaluation

On an evaluation of the simulation input node when there is no previous
state, the node's inputs are evaluated and passed directly to the
outputs. Currently this a bit confusing, since they are first converted
into a simulation state and _then_ passed to the outputs. This commit
simplifies the node to avoid creating a simulation state, just moving
the values directly instead. The inputs are also set to unused when
there is a previous state too.
---
 .../nodes/node_geo_simulation_input.cc        | 38 ++++++++++---------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/source/blender/nodes/geometry/nodes/node_geo_simulation_input.cc b/source/blender/nodes/geometry/nodes/node_geo_simulation_input.cc
index 045a610f9b5..4fa74f3ef20 100644
--- a/source/blender/nodes/geometry/nodes/node_geo_simulation_input.cc
+++ b/source/blender/nodes/geometry/nodes/node_geo_simulation_input.cc
@@ -57,7 +57,7 @@ class LazyFunctionForSimulationInputNode final : public LazyFunction {
   {
     const GeoNodesLFUserData &user_data = *static_cast<const GeoNodesLFUserData *>(
         context.user_data);
-    const GeoNodesModifierData &modifier_data = *user_data.modifier_data;
+    GeoNodesModifierData &modifier_data = *user_data.modifier_data;
     if (modifier_data.current_simulation_state == nullptr) {
       params.set_default_remaining_outputs();
       return;
@@ -71,13 +71,28 @@ class LazyFunctionForSimulationInputNode final : public LazyFunction {
     const bke::sim::SimulationZoneID zone_id = get_simulation_zone_id(*user_data.compute_context,
                                                                       output_node_id_);
 
+    Array<void *> output_values(simulation_items_.size());
+    for (const int i : simulation_items_.index_range()) {
+      output_values[i] = params.get_output_data_ptr(i + 1);
+    }
+
     const bke::sim::SimulationZoneState *prev_zone_state =
         modifier_data.prev_simulation_state == nullptr ?
             nullptr :
             modifier_data.prev_simulation_state->get_zone_state(zone_id);
 
-    std::optional<bke::sim::SimulationZoneState> initial_prev_zone_state;
-    if (prev_zone_state == nullptr) {
+    if (prev_zone_state) {
+      simulation_state_to_values(simulation_items_,
+                                 *prev_zone_state,
+                                 *modifier_data.self_object,
+                                 *user_data.compute_context,
+                                 node_,
+                                 output_values);
+      for (const int i : inputs_.index_range()) {
+        params.set_input_unused(i);
+      }
+    }
+    else {
       Array<void *> input_values(simulation_items_.size(), nullptr);
       for (const int i : simulation_items_.index_range()) {
         input_values[i] = params.try_get_input_data_ptr_or_request(i);
@@ -86,22 +101,11 @@ class LazyFunctionForSimulationInputNode final : public LazyFunction {
         /* Wait until all inputs are available. */
         return;
       }
-
-      initial_prev_zone_state.emplace();
-      values_to_simulation_state(simulation_items_, input_values, *initial_prev_zone_state);
-      prev_zone_state = &*initial_prev_zone_state;
+      for (const int i : input_values.index_range()) {
+        inputs_[i].type->move_construct(input_values[i], output_values[i]);
+      }
     }
 
-    Array<void *> output_values(simulation_items_.size());
-    for (const int i : simulation_items_.index_range()) {
-      output_values[i] = params.get_output_data_ptr(i + 1);
-    }
-    simulation_state_to_values(simulation_items_,
-                               *prev_zone_state,
-                               *modifier_data.self_object,
-                               *user_data.compute_context,
-                               node_,
-                               output_values);
     for (const int i : simulation_items_.index_range()) {
       params.output_set(i + 1);
     }
-- 
2.30.2