Add a random offset to the ray marching algorithm

Assets/ScriptableRenderPipeline/Core/ShaderLibrary/Common.hlsl

 #endif
 #include "API/Validate.hlsl"
 
-#include "Noise.hlsl"
+#include "Random.hlsl"
 
 // Some shader compiler don't support to do multiple ## for concatenation inside the same macro, it require an indirection.
 // This is the purpose of this macro

Assets/ScriptableRenderPipeline/HDRenderPipeline/HDRenderPipeline.cs

                                                                                                : "VolumetricLightingAllLights");
                 hdCamera.SetupComputeShader(m_VolumetricLightingCS, cmd);
 
-                // TODO: replace strings with nameIDs.
+                cmd.SetComputeVectorParam( m_VolumetricLightingCS, HDShaderIDs._Time,          Shader.GetGlobalVector(HDShaderIDs._Time));
 
                 // Pass clustered light data (if present) into the compute shader.
                 m_LightLoop.PushGlobalParams(hdCamera.camera, cmd, m_VolumetricLightingCS, m_VolumetricLightingKernel, true);

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/Volumetrics/Resources/VolumetricLighting.compute

 
     float maxDepthVS = posInput.depthVS;
 
-    float du = rcp(numSteps);           // Compile-time constant
-    float u0 = 0.5 * du;                // Compile-time constant
+    // Note: we are already using 'unPositionSS' for randomization of LODDitheringTransition().
+    float zeta = GenerateHashedRandomFloat(posInput.unPositionSS.yx);
+
+    float du = rcp(numSteps);
+    float u0 = 0.25 * du + 0.5 * du * zeta;
     float dt = du * ray.maxLength;
 
     float3 radiance = 0;

Assets/ScriptableRenderPipeline/Core/ShaderLibrary/Random.hlsl.meta

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Assets/ScriptableRenderPipeline/Core/ShaderLibrary/Noise.hlsl.meta

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