From be395304ec7b12f548388920819e5d0b2f98051e Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Thu, 19 Sep 2024 10:11:49 +0200
Subject: [PATCH] Fix Pre-Skinned Normal and Position when accessed in Pixel
 Shader

#2549
---
 .../MaterialGenerator.Material.cpp            | 40 ++++---------------
 .../MaterialGenerator/MaterialGenerator.cpp   | 28 +++++++++++++
 .../MaterialGenerator/MaterialGenerator.h     |  1 +
 3 files changed, 36 insertions(+), 33 deletions(-)

diff --git a/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Material.cpp b/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Material.cpp
index 03b27bfa1..f56f7843c 100644
--- a/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Material.cpp
+++ b/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Material.cpp
@@ -183,11 +183,15 @@ void MaterialGenerator::ProcessGroupMaterial(Box* box, Node* node, Value& value)
         break;
     // Pre-skinned Local Position
     case 13:
-        value = _treeType == MaterialTreeType::VertexShader ? Value(VariantType::Float3, TEXT("input.PreSkinnedPosition")) : Value::Zero;
+        value = Value(VariantType::Float3, TEXT("input.PreSkinnedPosition"));
+        if (_treeType != MaterialTreeType::VertexShader)
+            value = VsToPs(node, box).AsFloat3();
         break;
     // Pre-skinned Local Normal
     case 14:
-        value = _treeType == MaterialTreeType::VertexShader ? Value(VariantType::Float3, TEXT("input.PreSkinnedNormal")) : Value::Zero;
+        value = Value(VariantType::Float3, TEXT("input.PreSkinnedNormal"));
+        if (_treeType != MaterialTreeType::VertexShader)
+            value = VsToPs(node, box).AsFloat3();
         break;
     // Depth
     case 15:
@@ -211,38 +215,8 @@ void MaterialGenerator::ProcessGroupMaterial(Box* box, Node* node, Value& value)
         break;
     // Interpolate VS To PS
     case 20:
-    {
-        const auto input = node->GetBox(0);
-
-        // If used in VS then pass the value from the input box
-        if (_treeType == MaterialTreeType::VertexShader)
-        {
-            value = tryGetValue(input, Value::Zero).AsFloat4();
-            break;
-        }
-
-        // Check if can use more interpolants
-        if (_vsToPsInterpolants.Count() == 16)
-        {
-            OnError(node, box, TEXT("Too many VS to PS interpolants used."));
-            value = Value::Zero;
-            break;
-        }
-
-        // Check if can use interpolants
-        const auto layer = GetRootLayer();
-        if (!layer || layer->Domain == MaterialDomain::Decal || layer->Domain == MaterialDomain::PostProcess)
-        {
-            OnError(node, box, TEXT("VS to PS interpolants are not supported in Decal or Post Process materials."));
-            value = Value::Zero;
-            break;
-        }
-
-        // Indicate the interpolator slot usage
-        value = Value(VariantType::Float4, String::Format(TEXT("input.CustomVSToPS[{0}]"), _vsToPsInterpolants.Count()));
-        _vsToPsInterpolants.Add(input);
+        value = VsToPs(node, node->GetBox(0));
         break;
-    }
     // Terrain Holes Mask
     case 21:
     {
diff --git a/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.cpp b/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.cpp
index f9ca26705..858a6dc4f 100644
--- a/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.cpp
+++ b/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.cpp
@@ -832,4 +832,32 @@ void MaterialGenerator::WriteCustomGlobalCode(const Array<const MaterialGraph::N
     }
 }
 
+ShaderGenerator::Value MaterialGenerator::VsToPs(Node* node, Box* input)
+{
+    // If used in VS then pass the value from the input box
+    if (_treeType == MaterialTreeType::VertexShader)
+    {
+        return tryGetValue(input, Value::Zero).AsFloat4();
+    }
+
+    // Check if can use more interpolants
+    if (_vsToPsInterpolants.Count() == 16)
+    {
+        OnError(node, input, TEXT("Too many VS to PS interpolants used."));
+        return Value::Zero;
+    }
+
+    // Check if can use interpolants
+    const auto layer = GetRootLayer();
+    if (!layer || layer->Domain == MaterialDomain::Decal || layer->Domain == MaterialDomain::PostProcess)
+    {
+        OnError(node, input, TEXT("VS to PS interpolants are not supported in Decal or Post Process materials."));
+        return Value::Zero;
+    }
+
+    // Indicate the interpolator slot usage
+    _vsToPsInterpolants.Add(input);
+    return Value(VariantType::Float4, String::Format(TEXT("input.CustomVSToPS[{0}]"), _vsToPsInterpolants.Count() - 1));
+}
+
 #endif
diff --git a/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.h b/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.h
index 0e55192c1..980148d97 100644
--- a/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.h
+++ b/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.h
@@ -205,6 +205,7 @@ private:
     MaterialValue AccessParticleAttribute(Node* caller, const StringView& name, ParticleAttributeValueTypes valueType, const Char* index = nullptr, ParticleAttributeSpace space = ParticleAttributeSpace::AsIs);
     void prepareLayer(MaterialLayer* layer, bool allowVisibleParams);
     void WriteCustomGlobalCode(const Array<const MaterialGraph::Node*, InlinedAllocation<8>>& nodes, int32 templateInputsMapping);
+    Value VsToPs(Node* node, Box* input);
 
 public: