Fixed the intensity of the sky being reduced signficantly even if there is no clouds (case 1388279). #6601

Author: anisunity

TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/LinuxEditor/Vulkan/None/5011_VolumetricClouds.png

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed the fade in mode of the clouds not impacting the volumetric clouds shadows (case 1381652).
 - Fixed issue with typed loads on RGBA16F in Volumetric Lighting Filtering.
 - Fixed potential asymmetrical resource release in the volumetric clouds (case 1388218).
+- Fixed the intensity of the sky being reduced signficantly even if there is no clouds (case 1388279).
 
 ## [13.1.4] - 2021-12-04
 

TestProjects/HDRP_Tests/Assets/ReferenceImages/Linear/OSXEditor/Metal/None/5011_VolumetricClouds.png

@@ -61,6 +61,8 @@
 #define MAX_SKYBOX_VOLUMETRIC_CLOUDS_DISTANCE 200000.0f
 // Maximal size of a light step
 #define LIGHT_STEP_MAXIMAL_SIZE 1000.0f
+// Threshold at which the clouds are considered inexistant (Found experimentally)
+#define TRANSMITTANCE_DISCARD_THRESHOLD 0.992
 
 // HDRP generic includes
 #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
@@ -1383,6 +1385,9 @@ void UPSAMPLE_KERNEL(uint3 finalCoord : SV_DispatchThreadID,
     currentClouds.xyz = unapplyFastTonemapping(currentClouds.xyz);
     currentClouds.w = saturate(currentClouds.w);
 
+    // Due to numerical precision issues, upscaling a bunch of 1.0 can lead to a slightly lower number, this fixes it.
+    currentClouds.w = currentClouds.w > TRANSMITTANCE_DISCARD_THRESHOLD ? 1.0 : currentClouds.w;
+
 #ifdef LOCAL_VOLUMETRIC_CLOUDS
     float cloudDepth = GetCloudDepth_LDS(groupThreadId, IndexToLocalOffsetCoords[closestNeighbor]);
 #else
@@ -1460,6 +1465,9 @@ void UPSAMPLE_KERNEL_SKY(uint3 finalCoord : SV_DispatchThreadID,
     currentClouds.xyz = unapplyFastTonemapping(currentClouds.xyz);
     currentClouds.w = saturate(currentClouds.w);
 
+    // Due to numerical precision issues, upscaling a bunch of 1.0 can lead to a slightly lower number, this fixes it.
+    currentClouds.w = currentClouds.w > TRANSMITTANCE_DISCARD_THRESHOLD ? 1.0 : currentClouds.w;
+
     // Store the upscaled result only, composite in later pass.
     _VolumetricCloudsUpscaleTextureRW[COORD_TEXTURE2D_X(finalCoord.xy)] = currentClouds;
 }
@@ -1491,6 +1499,9 @@ void COMBINE_KERNEL(uint3 finalCoord : SV_DispatchThreadID,
     currentClouds.xyz = unapplyFastTonemapping(currentClouds.xyz);
     currentClouds.w = saturate(currentClouds.w);
 
+    // Due to numerical precision issues, upscaling a bunch of 1.0 can lead to a slightly lower number, this fixes it.
+    currentClouds.w = currentClouds.w > TRANSMITTANCE_DISCARD_THRESHOLD ? 1.0 : currentClouds.w;
+
 #ifdef LOCAL_VOLUMETRIC_CLOUDS
     float cloudsDepth = LOAD_TEXTURE2D_X(_DepthStatusTexture, finalCoord.xy).z;
 #else
@@ -1546,6 +1557,9 @@ void COMBINE_KERNEL_SKY(uint3 finalCoord : SV_DispatchThreadID)
     currentClouds.xyz = unapplyFastTonemapping(currentClouds.xyz);
     currentClouds.w = saturate(currentClouds.w);
 
+    // Due to numerical precision issues, upscaling a bunch of 1.0 can lead to a slightly lower number, this fixes it.
+    currentClouds.w = currentClouds.w > TRANSMITTANCE_DISCARD_THRESHOLD ? 1.0 : currentClouds.w;
+
     // Store the upscaled result only, composite in later pass.
     _VolumetricCloudsUpscaleTextureRW[COORD_TEXTURE2D_X(finalCoord.xy)] = currentClouds;
 }