Changed the clamping approach for RTR and RTGI (in both perf and quality) to improve visual quality.

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -57,6 +57,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Decreased the minimal Fog Distance value in the Density Volume to 0.05.
 - Changed the convergence time of ssgi to 16 frames and the preset value
 - Improved robustness of volumetric sampling in path tracing (case 1295187).
+- Changed the clamping approach for RTR and RTGI (in both perf and quality) to improve visual quality.
 
 ## [10.3.0] - 2020-12-01
 

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/HDRaytracingIndirectDiffuse.cs

@@ -84,7 +84,6 @@ DeferredLightingRTParameters PrepareIndirectDiffuseDeferredLightingRTParameters(
             deferredParameters.raytracingCB._RaytracingIntensityClamp = settings.clampValue;
             deferredParameters.raytracingCB._RaytracingPreExposition = 1;
             deferredParameters.raytracingCB._RaytracingIncludeSky = 1;
-            deferredParameters.raytracingCB._RaytracingPreExposition = 1;
             deferredParameters.raytracingCB._RaytracingRayMaxLength = settings.rayLength;
             deferredParameters.raytracingCB._RayTracingDiffuseLightingOnly = 1;
 

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/Deferred/RaytracingDeferred.compute

@@ -62,9 +62,14 @@ void RAYTRACING_DEFERRED(uint3 dispatchThreadId : SV_DispatchThreadID, uint2 gro
     // If the distance is negative, this means it is a sky pixel or an unlit material
     if (LOAD_TEXTURE2D_X(_RaytracingDistanceBuffer, currentCoord).x < 0.0)
     {
-        float3 newSampleColor = clamp(LOAD_TEXTURE2D_X(_GBufferTexture3, currentCoord).rgb * GetCurrentExposureMultiplier(), 0.0, _RaytracingIntensityClamp)
-                                * (_RaytracingPreExposition ? 1.0 : GetInverseCurrentExposureMultiplier() );
-        _RaytracingLitBufferRW[COORD_TEXTURE2D_X(currentCoord)] = float4(newSampleColor, 0.0);
+        // Convert to HSV space
+        float3 finalColor = RgbToHsv(LOAD_TEXTURE2D_X(_GBufferTexture3, currentCoord).rgb * GetCurrentExposureMultiplier());
+
+        // Expose and clamp the final color
+        finalColor.z = clamp(finalColor.z, 0.0, _RaytracingIntensityClamp);
+
+        // Convert back to HSV space
+        _RaytracingLitBufferRW[COORD_TEXTURE2D_X(currentCoord)] = float4(HsvToRgb(finalColor) * (_RaytracingPreExposition ? 1.0 : GetInverseCurrentExposureMultiplier()), 0.0);
         return;
     }
 
@@ -106,8 +111,23 @@ void RAYTRACING_DEFERRED(uint3 dispatchThreadId : SV_DispatchThreadID, uint2 gro
     float3 finalColor = (diffuseLighting + specularLighting);
     // Apply fog attenuation
     ApplyFogAttenuation(sourcePosInput.positionWS, rayDirection, rayDistance, finalColor, true);
-    // Expose, clamp and inverse exposure
-    finalColor = clamp(finalColor * GetCurrentExposureMultiplier(), 0.0, _RaytracingIntensityClamp) * (_RaytracingPreExposition ? 1.0 : GetInverseCurrentExposureMultiplier());
+
+    // Expose, clamp and inverse exposure. Though depending on the signal nature we go for different clamping strategies
+    if (_RaytracingPreExposition)
+    {
+        // Convert to HSV space
+        finalColor = RgbToHsv(finalColor * GetCurrentExposureMultiplier());
+
+        // Expose and clamp the final color
+        finalColor.z = clamp(finalColor.z, 0.0, _RaytracingIntensityClamp);
+
+        // Convert back to HSV space
+        finalColor = HsvToRgb(finalColor);
+    }
+    else
+    {
+        finalColor = clamp(finalColor * GetCurrentExposureMultiplier(), 0.0, _RaytracingIntensityClamp) * GetInverseCurrentExposureMultiplier();
+    }
     _RaytracingLitBufferRW[COORD_TEXTURE2D_X(currentCoord)] = float4(finalColor, 1.0);
 }
 

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/IndirectDiffuse/RaytracingIndirectDiffuse.raytrace

@@ -128,9 +128,14 @@ void RayGenIntegration()
    	// Normalize the value
     finalColor *= 1.0f / _RaytracingNumSamples;
 
+    // Convert to HSV space
+    finalColor = RgbToHsv(finalColor * GetCurrentExposureMultiplier());
+
     // Expose and clamp the final color
-    finalColor = clamp(finalColor * GetCurrentExposureMultiplier(), 0.0, _RaytracingIntensityClamp);
+    finalColor.z = clamp(finalColor.z, 0.0, _RaytracingIntensityClamp);
 
+    // Convert back to HSV space
+    finalColor = HsvToRgb(finalColor) * GetInverseCurrentExposureMultiplier();
     // We store the sampled color and the weight that shall be used for it (1.0f)
     _IndirectDiffuseTextureRW[COORD_TEXTURE2D_X(currentCoord)] = float4(finalColor, 1.0f);
 }

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/Reflections/RaytracingReflections.raytrace

@@ -156,16 +156,32 @@ void RayGenIntegration()
         // Evaluate the ray intersection
         TraceRay(_RaytracingAccelerationStructure, RAY_FLAG_CULL_BACK_FACING_TRIANGLES, RAYTRACINGRENDERERFLAG_REFLECTION, 0, 1, 0, rayDescriptor, rayIntersection);
 
+        // The clamping process is different for the sky and rest
+        float3 sampleColor = 0.0;
+        if (rayIntersection.t == _RaytracingRayMaxLength)
+        {
+            // Convert to HSV space
+            sampleColor = RgbToHsv(rayIntersection.color * GetCurrentExposureMultiplier());
+
+            // Expose and clamp the final color
+            sampleColor.z = clamp(sampleColor.z, 0.0, _RaytracingIntensityClamp);
+
+            // Convert back to HSV space
+            sampleColor = HsvToRgb(sampleColor) * GetInverseCurrentExposureMultiplier();
+        }
+        else
+        {
+            // Expose and clamp the final color
+            sampleColor = clamp(rayIntersection.color * GetCurrentExposureMultiplier(), 0.0, _RaytracingIntensityClamp) * GetInverseCurrentExposureMultiplier();
+        }
+
         // Contribute to the pixel
-        finalColor += rayIntersection.color;
+        finalColor += sampleColor;
     }
 
    	// Normalize the value
     finalColor *= 1.0 / realSampleCount;
 
-    // Expose and clamp the final color
-    finalColor = clamp(finalColor * GetCurrentExposureMultiplier(), 0.0, _RaytracingIntensityClamp) * GetInverseCurrentExposureMultiplier();
-
     // We also need to compute the fade factor for this sample
     float weightValue = _RaytracingReflectionSmoothnessFadeStart == _RaytracingReflectionMinSmoothness ? 1.0 : saturate((perceptualSmoothness - _RaytracingReflectionMinSmoothness) / (_RaytracingReflectionSmoothnessFadeStart -_RaytracingReflectionMinSmoothness));
 
@@ -252,8 +268,24 @@ void RayGenIntegrationTransparent()
     // Evaluate the ray intersection
     TraceRay(_RaytracingAccelerationStructure, RAY_FLAG_CULL_BACK_FACING_TRIANGLES, RAYTRACINGRENDERERFLAG_REFLECTION, 0, 1, 0, rayDescriptor, rayIntersection);
 
-    // Expose and clamp the final color
-    float3 finalColor = clamp(rayIntersection.color * GetCurrentExposureMultiplier(), 0.0, _RaytracingIntensityClamp) * GetInverseCurrentExposureMultiplier();
+    // The clamping process is different for the sky and rest
+    float3 finalColor = 0.0;
+    if (rayIntersection.t == _RaytracingRayMaxLength)
+    {
+        // Convert to HSV space
+        finalColor = RgbToHsv(rayIntersection.color * GetCurrentExposureMultiplier());
+
+        // Expose and clamp the final color
+        finalColor.z = clamp(finalColor.z, 0.0, _RaytracingIntensityClamp);
+
+        // Convert back to HSV space
+        finalColor = HsvToRgb(finalColor) * GetInverseCurrentExposureMultiplier();
+    }
+    else
+    {
+        // Expose and clamp the final color
+        finalColor = clamp(rayIntersection.color * GetCurrentExposureMultiplier(), 0.0, _RaytracingIntensityClamp) * GetInverseCurrentExposureMultiplier();
+    }
 
     // We store the sampled color and the weight that shall be used for it (1.0)
     _SsrLightingTextureRW[COORD_TEXTURE2D_X(currentCoord)] = float4(finalColor, 1.0);