From 2f1f3800622f989039e62b690a09161beaff5074 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Tue, 7 Oct 2025 18:10:14 +0200
Subject: [PATCH] Add new scene textures `SceneStencil` and `ObjectLayer` to
 sample Stencil buffer

---
 Source/Engine/Graphics/Materials/MaterialInfo.h | 10 ++++++++++
 .../Graphics/Materials/MaterialParams.cpp       |  4 ++++
 .../GPU/ParticleEmitterGraph.GPU.Textures.cpp   |  2 ++
 .../MaterialGenerator.Textures.cpp              | 17 +++++++++++++++++
 Source/Engine/Visject/ShaderGraphUtilities.cpp  |  5 ++++-
 5 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/Source/Engine/Graphics/Materials/MaterialInfo.h b/Source/Engine/Graphics/Materials/MaterialInfo.h
index 69a9bd0a6..84771fed8 100644
--- a/Source/Engine/Graphics/Materials/MaterialInfo.h
+++ b/Source/Engine/Graphics/Materials/MaterialInfo.h
@@ -444,6 +444,16 @@ API_ENUM() enum class MaterialSceneTextures
     /// The scene world-space position (relative to the render view origin).
     /// </summary>
     WorldPosition = 11,
+
+    /// <summary>
+    /// The scene stencil.
+    /// </summary>
+    SceneStencil = 12,
+
+    /// <summary>
+    /// The object layer index.
+    /// </summary>
+    ObjectLayer = 13,
 };
 
 /// <summary>
diff --git a/Source/Engine/Graphics/Materials/MaterialParams.cpp b/Source/Engine/Graphics/Materials/MaterialParams.cpp
index 2fa5a8e5f..05bb29c4a 100644
--- a/Source/Engine/Graphics/Materials/MaterialParams.cpp
+++ b/Source/Engine/Graphics/Materials/MaterialParams.cpp
@@ -393,6 +393,10 @@ void MaterialParameter::Bind(BindMeta& meta) const
             case MaterialSceneTextures::Specular:
                 view = meta.CanSampleGBuffer ? meta.Buffers->GBuffer2->View() : nullptr;
                 break;
+            case MaterialSceneTextures::SceneStencil:
+            case MaterialSceneTextures::ObjectLayer:
+                view = meta.CanSampleDepth ? meta.Buffers->DepthBuffer->ViewStencil() : nullptr;
+                break;
             default: ;
             }
         }
diff --git a/Source/Engine/Particles/Graph/GPU/ParticleEmitterGraph.GPU.Textures.cpp b/Source/Engine/Particles/Graph/GPU/ParticleEmitterGraph.GPU.Textures.cpp
index 820f8da3d..ed4f5f0e3 100644
--- a/Source/Engine/Particles/Graph/GPU/ParticleEmitterGraph.GPU.Textures.cpp
+++ b/Source/Engine/Particles/Graph/GPU/ParticleEmitterGraph.GPU.Textures.cpp
@@ -246,6 +246,8 @@ void ParticleEmitterGPUGenerator::ProcessGroupTextures(Box* box, Node* node, Val
             break;
         }
         case MaterialSceneTextures::WorldPosition:
+        case MaterialSceneTextures::SceneStencil:
+        case MaterialSceneTextures::ObjectLayer:
             value = Value::Zero; // Not implemented
             break;
         default:
diff --git a/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Textures.cpp b/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Textures.cpp
index 6bd88f2ae..c48a4c569 100644
--- a/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Textures.cpp
+++ b/Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Textures.cpp
@@ -474,6 +474,23 @@ void MaterialGenerator::ProcessGroupTextures(Box* box, Node* node, Value& value)
             value = writeLocal(VariantType::Float3, String::Format(TEXT("GetWorldPos({1}, {0}.rgb)"), depthSample->Value, uv), node);
             break;
         }
+        case MaterialSceneTextures::SceneStencil:
+        case MaterialSceneTextures::ObjectLayer:
+        {
+            auto stencilParam = findOrAddSceneTexture(MaterialSceneTextures::SceneStencil);
+            const auto parent = box->GetParent<ShaderGraphNode<>>();
+            MaterialGraphBox* uvBox = parent->GetBox(0);
+            bool useCustomUVs = uvBox->HasConnection();
+            String uv;
+            if (useCustomUVs)
+                uv = MaterialValue::Cast(tryGetValue(uvBox, getUVs), VariantType::Float2).Value;
+            else
+                uv = TEXT("input.TexCoord.xy");
+            const Char* func = type == MaterialSceneTextures::ObjectLayer ? TEXT("STENCIL_BUFFER_OBJECT_LAYER") : TEXT("");
+            value = writeLocal(VariantType::Int, String::Format(TEXT("{2}(STENCIL_BUFFER_LOAD({0}, {1} * ScreenSize.xy))"), stencilParam.ShaderName, uv, func), node);
+            _includes.Add(TEXT("./Flax/Stencil.hlsl"));
+            break;
+        }
         default:
         {
             // Sample single texture
diff --git a/Source/Engine/Visject/ShaderGraphUtilities.cpp b/Source/Engine/Visject/ShaderGraphUtilities.cpp
index 83db4590a..bdcb55c05 100644
--- a/Source/Engine/Visject/ShaderGraphUtilities.cpp
+++ b/Source/Engine/Visject/ShaderGraphUtilities.cpp
@@ -157,7 +157,10 @@ const Char* ShaderGraphUtilities::GenerateShaderResources(TextWriterUnicode& wri
         case MaterialParameterType::GPUTexture:
         case MaterialParameterType::SceneTexture:
         case MaterialParameterType::Texture:
-            format = TEXT("Texture2D {0} : register(t{1});");
+            if (param.AsInteger == (int32)MaterialSceneTextures::SceneStencil)
+                format = TEXT("Texture2D<uint2> {0} : register(t{1});");
+            else
+                format = TEXT("Texture2D {0} : register(t{1});");
             break;
         case MaterialParameterType::GPUTextureCube:
         case MaterialParameterType::CubeTexture: