Fix missing particle layout attributes when using Particle Emitter Function

#1640

Source/Engine/Particles/Graph/ParticleEmitterGraph.h

@@ -37,12 +37,12 @@ public:
     /// <summary>
     /// Flag valid for used particle nodes that need per-particle data to evaluate its value (including dependant nodes linked to input boxes). Used to skip per-particle graph evaluation if graph uses the same value for all particles (eg. is not using per-particle seed or position node).
     /// </summary>
-    bool UsesParticleData;
+    bool UsesParticleData = false;
 
     /// <summary>
     /// Flag valid for used particle nodes that result in constant data (nothing random nor particle data).
     /// </summary>
-    bool IsConstant;
+    bool IsConstant = true;
 
     /// <summary>
     /// The cached particle attribute indices used by the simulation graph to access particle properties.
@@ -50,6 +50,8 @@ public:
     int32 Attributes[PARTICLE_EMITTER_MAX_ATTRIBUTES_REFS_PER_NODE];
 };
 
+void InitParticleEmitterFunctionCall(const Guid& assetId, AssetReference<Asset>& asset, bool& usesParticleData, ParticleLayout& layout);
+
 /// <summary>
 /// The Particle Emitter Graph used to simulate particles.
 /// </summary>
@@ -157,8 +159,6 @@ public:
         if (node->Used)
             return;
         node->Used = true;
-        node->UsesParticleData = false;
-        node->IsConstant = true;
 
 #define USE_ATTRIBUTE(name, valueType, slot) \
 	{ \
@@ -292,14 +292,11 @@ public:
         case GRAPH_NODE_MAKE_TYPE(14, 214):
         case GRAPH_NODE_MAKE_TYPE(14, 215):
         case GRAPH_NODE_MAKE_TYPE(14, 216):
-        {
             node->IsConstant = false;
             break;
-        }
         // Particle Emitter Function
         case GRAPH_NODE_MAKE_TYPE(14, 300):
-            node->Assets[0] = Content::LoadAsync<Asset>((Guid)node->Values[0]);
+            InitParticleEmitterFunctionCall((Guid)node->Values[0], node->Assets[0], node->UsesParticleData, Layout);
-            node->UsesParticleData = true; // TODO: analyze emitter function graph to detect if it's actually using any particle data at all (even from inputs after inline)
             break;
         // Particle Index
         case GRAPH_NODE_MAKE_TYPE(14, 301):
@@ -564,7 +561,7 @@ public:
             return true;
 
         // Compute particle data layout and initialize used nodes (for only used nodes, start depth searching rom the modules)
-        Layout.AddAttribute(TEXT("Position"), ParticleAttribute::ValueTypes::Float3);
+        //Layout.AddAttribute(TEXT("Position"), ParticleAttribute::ValueTypes::Float3);
 #define PROCESS_MODULES(modules) for (int32 i = 0; i < modules.Count(); i++) { modules[i]->Used = false; InitializeNode(modules[i]); }
         PROCESS_MODULES(SpawnModules);
         PROCESS_MODULES(InitModules);

Source/Engine/Particles/ParticleEmitterFunction.cpp

@@ -9,6 +9,27 @@
 #endif
 #include "Engine/Content/Factories/BinaryAssetFactory.h"
 
+void InitParticleEmitterFunctionCall(const Guid& assetId, AssetReference<Asset>& asset, bool& usesParticleData, ParticleLayout& layout)
+{
+    const auto function = Content::Load<ParticleEmitterFunction>(assetId);
+    asset = function;
+    if (function)
+    {
+        // Insert any used particle data into the calling graph
+        for (const ParticleAttribute& e : function->Graph.Layout.Attributes)
+        {
+            if (layout.FindAttribute(e.Name, e.ValueType) == -1)
+                layout.AddAttribute(e.Name, e.ValueType);
+        }
+
+        // Detect if function needs to be evaluated per-particle
+        for (int32 i = 0; i < function->Outputs.Count() && !usesParticleData; i++)
+        {
+            usesParticleData = function->Graph.Nodes[function->Outputs.Get()[i]].UsesParticleData;
+        }
+    }
+}
+
 REGISTER_BINARY_ASSET(ParticleEmitterFunction, "FlaxEngine.ParticleEmitterFunction", false);
 
 ParticleEmitterFunction::ParticleEmitterFunction(const SpawnParams& params, const AssetInfo* info)

Source/Engine/Visject/VisjectGraph.h

@@ -262,11 +262,11 @@ protected:
 
     FORCE_INLINE Value tryGetValue(Box* box)
     {
-        return box && box->HasConnection() ? eatBox(box->GetParent<Node>(), box->FirstConnection()) : Value::Zero;
+        return box && box->Connections.HasItems() ? eatBox(box->GetParent<Node>(), (VisjectGraphBox*)box->Connections.Get()[0]) : Value::Zero;
     }
 
     FORCE_INLINE Value tryGetValue(Box* box, const Value& defaultValue)
     {
-        return box && box->HasConnection() ? eatBox(box->GetParent<Node>(), box->FirstConnection()) : defaultValue;
+        return box && box->Connections.HasItems() ? eatBox(box->GetParent<Node>(), (VisjectGraphBox*)box->Connections.Get()[0]) : defaultValue;
     }
 };