Add smooth light brightness fade out at last 10% of ViewDistance (if used)

Source/Engine/Level/Actors/DirectionalLight.cpp

@@ -18,11 +18,11 @@ void DirectionalLight::Draw(RenderContext& renderContext)
 {
     float brightness = Brightness;
     AdjustBrightness(renderContext.View, brightness);
-    const Float3 position = GetPosition() - renderContext.View.Origin;
+    Float3 position;
     if (Brightness > ZeroTolerance
         && EnumHasAnyFlags(renderContext.View.Flags, ViewFlags::DirectionalLights)
         && EnumHasAnyFlags(renderContext.View.Pass, DrawPass::GBuffer)
-        && (ViewDistance < ZeroTolerance || Float3::DistanceSquared(renderContext.View.Position, position) < ViewDistance * ViewDistance))
+        && CheckViewDistance(renderContext.View.Position, renderContext.View.Origin, position, brightness))
     {
         RenderDirectionalLightData data;
         data.Position = position;

Source/Engine/Level/Actors/Light.h

@@ -29,7 +29,7 @@ public:
     float Brightness = 3.14f;
 
     /// <summary>
-    /// Controls light visibility range. The distance at which the light becomes completely faded. Use a value of 0 to always draw light.
+    /// Controls light visibility range. The distance at which the light becomes completely faded (blend happens on the last 10% of that range). Use a value of 0 to always draw light.
     /// </summary>
     API_FIELD(Attributes="EditorOrder(35), Limit(0, float.MaxValue, 10.0f), EditorDisplay(\"Light\")")
     float ViewDistance = 0.0f;
@@ -56,6 +56,19 @@ protected:
     // Adjust the light brightness used during rendering (called by light types inside SetupLightData callback)
     void AdjustBrightness(const RenderView& view, float& brightness) const;
 
+    FORCE_INLINE bool CheckViewDistance(const Float3& viewPosition, const Float3& viewOrigin, Float3& position, float& brightness) const
+    {
+        position = _transform.Translation - viewOrigin;
+        if (ViewDistance > ZeroTolerance)
+        {
+            const float dst2 = Vector3::DistanceSquared(viewPosition, position);
+            const float dst = Math::Sqrt(dst2);
+            brightness *= Math::Remap(dst, 0.9f * ViewDistance, ViewDistance, 1.0f, 0.0f);
+            return dst < ViewDistance;
+        }
+        return true;
+    }
+
 public:
     // [Actor]
     void OnEnable() override;

Source/Engine/Level/Actors/PointLight.cpp

@@ -82,13 +82,13 @@ void PointLight::Draw(RenderContext& renderContext)
 {
     float brightness = ComputeBrightness();
     AdjustBrightness(renderContext.View, brightness);
-    const Float3 position = GetPosition() - renderContext.View.Origin;
+    Float3 position;
     const float radius = GetScaledRadius();
     if (EnumHasAnyFlags(renderContext.View.Flags, ViewFlags::PointLights)
         && EnumHasAnyFlags(renderContext.View.Pass, DrawPass::GBuffer)
         && brightness > ZeroTolerance
         && radius > ZeroTolerance
-        && (ViewDistance < ZeroTolerance || Vector3::DistanceSquared(renderContext.View.Position, position) < ViewDistance * ViewDistance))
+        && CheckViewDistance(renderContext.View.Position, renderContext.View.Origin, position, brightness))
     {
         RenderPointLightData data;
         data.Position = position;

Source/Engine/Level/Actors/SpotLight.cpp

@@ -130,7 +130,7 @@ void SpotLight::Draw(RenderContext& renderContext)
 {
     float brightness = ComputeBrightness();
     AdjustBrightness(renderContext.View, brightness);
-    const Float3 position = GetPosition() - renderContext.View.Origin;
+    Float3 position;
     const float radius = GetScaledRadius();
     const float outerConeAngle = GetOuterConeAngle();
     if (EnumHasAnyFlags(renderContext.View.Flags, ViewFlags::SpotLights)
@@ -138,7 +138,7 @@ void SpotLight::Draw(RenderContext& renderContext)
         && brightness > ZeroTolerance
         && radius > ZeroTolerance
         && outerConeAngle > ZeroTolerance
-        && (ViewDistance < ZeroTolerance || Vector3::DistanceSquared(renderContext.View.Position, position) < ViewDistance * ViewDistance))
+        && CheckViewDistance(renderContext.View.Position, renderContext.View.Origin, position, brightness))
     {
         RenderSpotLightData data;
         data.Position = position;