From f09d6aa0ebaf174b8cad9f6fa530c034b773ff21 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Tue, 30 Sep 2025 15:44:34 +0200
Subject: [PATCH] Fix fog rendering bug on d3d11/d3d10

---
 .../Editor/MaterialTemplates/Features/ForwardShading.hlsl | 8 +++++++-
 .../Engine/Graphics/Materials/MaterialShaderFeatures.cpp  | 3 +++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/Content/Editor/MaterialTemplates/Features/ForwardShading.hlsl b/Content/Editor/MaterialTemplates/Features/ForwardShading.hlsl
index 92f3bfd30..123201d1e 100644
--- a/Content/Editor/MaterialTemplates/Features/ForwardShading.hlsl
+++ b/Content/Editor/MaterialTemplates/Features/ForwardShading.hlsl
@@ -152,7 +152,13 @@ void PS_Forward(
 
 #if USE_FOG && MATERIAL_SHADING_MODEL != SHADING_MODEL_UNLIT
 	// Calculate exponential height fog
-	float4 fog = GetExponentialHeightFog(ExponentialHeightFog, materialInput.WorldPosition, ViewPos, 0, gBuffer.ViewPos.z);
+#if DIRECTX && FEATURE_LEVEL < FEATURE_LEVEL_SM6
+	// TODO: fix D3D11/D3D10 bug with incorrect distance
+	float fogSceneDistance = distance(materialInput.WorldPosition, ViewPos);
+#else
+	float fogSceneDistance = gBuffer.ViewPos.z;
+#endif
+	float4 fog = GetExponentialHeightFog(ExponentialHeightFog, materialInput.WorldPosition, ViewPos, 0, fogSceneDistance);
 
 	if (ExponentialHeightFog.VolumetricFogMaxDistance > 0)
 	{
diff --git a/Source/Engine/Graphics/Materials/MaterialShaderFeatures.cpp b/Source/Engine/Graphics/Materials/MaterialShaderFeatures.cpp
index a140fb577..64dfe8303 100644
--- a/Source/Engine/Graphics/Materials/MaterialShaderFeatures.cpp
+++ b/Source/Engine/Graphics/Materials/MaterialShaderFeatures.cpp
@@ -43,6 +43,9 @@ void ForwardShadingFeature::Bind(MaterialShader::BindParameters& params, Span<by
     else
     {
         data.ExponentialHeightFog.FogMinOpacity = 1.0f;
+        data.ExponentialHeightFog.FogDensity = 0.0f;
+        data.ExponentialHeightFog.FogCutoffDistance = 0.1f;
+        data.ExponentialHeightFog.StartDistance = 0.0f;
         data.ExponentialHeightFog.ApplyDirectionalInscattering = 0.0f;
     }
     params.GPUContext->BindSR(volumetricFogTextureRegisterIndex, volumetricFogTexture);