Fix height fog density calculation with large worlds

#3443

Source/Engine/Level/Actors/ExponentialHeightFog.cpp

@@ -128,9 +128,9 @@ bool ExponentialHeightFog::IntersectsItself(const Ray& ray, Real& distance, Vect
     return false;
 }
 
-void ExponentialHeightFog::GetVolumetricFogOptions(VolumetricFogOptions& result) const
+void ExponentialHeightFog::GetVolumetricFogOptions(const RenderView& view, VolumetricFogOptions& result) const
 {
-    const float height = (float)GetPosition().Y;
+    const float height = (float)(GetPosition().Y - view.Origin.Y);
     const float density = FogDensity / 1000.0f;
     const float heightFalloff = FogHeightFalloff / 1000.0f;
 
@@ -145,7 +145,7 @@ void ExponentialHeightFog::GetVolumetricFogOptions(VolumetricFogOptions& result)
 
 void ExponentialHeightFog::GetExponentialHeightFogData(const RenderView& view, ShaderExponentialHeightFogData& result) const
 {
-    const float height = (float)GetPosition().Y;
+    const float height = (float)(GetPosition().Y - view.Origin.Y);
     const float density = FogDensity / 1000.0f;
     const float heightFalloff = FogHeightFalloff / 1000.0f;
     const float viewHeight = view.Position.Y;

Source/Engine/Level/Actors/ExponentialHeightFog.h

@@ -154,7 +154,7 @@ public:
     bool IntersectsItself(const Ray& ray, Real& distance, Vector3& normal) override;
 
     // [IFogRenderer]
-    void GetVolumetricFogOptions(VolumetricFogOptions& result) const override;
+    void GetVolumetricFogOptions(const RenderView& view, VolumetricFogOptions& result) const override;
     void GetExponentialHeightFogData(const RenderView& view, ShaderExponentialHeightFogData& result) const override;
     void DrawFog(GPUContext* context, RenderContext& renderContext, GPUTextureView* output) override;
 

Source/Engine/Renderer/DrawCall.h

@@ -80,8 +80,9 @@ public:
     /// <summary>
     /// Gets the volumetric fog options.
     /// </summary>
+    /// <param name="view">The rendering view.</param>
     /// <param name="result">The result.</param>
-    virtual void GetVolumetricFogOptions(VolumetricFogOptions& result) const = 0;
+    virtual void GetVolumetricFogOptions(const RenderView& view, VolumetricFogOptions& result) const = 0;
 
     /// <summary>
     /// Gets the exponential height fog data.

Source/Engine/Renderer/RenderList.cpp

@@ -228,7 +228,7 @@ void RenderFogData::Init(const RenderView& view, IFogRenderer* renderer)
 {
     Renderer = renderer;
     renderer->GetExponentialHeightFogData(view, ExponentialHeightFogData);
-    renderer->GetVolumetricFogOptions(VolumetricFog);
+    renderer->GetVolumetricFogOptions(view, VolumetricFog);
     if (!VolumetricFog.UseVolumetricFog())
     {
         ExponentialHeightFogData.VolumetricFogMaxDistance = -1;