DGI propagation fixes (#112)

* Fixed fallback radiance baking when dirty flags are enabled.
* Fixed noticeable intensity loss for lower propagation quality due to axis weights renormalization error.
* Separate radiance comparison for LogLUV encoding that avoids many false positives in dirty flags.
* Fixed propagation data not being cleared when Frame Settings are changed via the settings window causing the pipeline to be destroyed.

Author: AndrewSaraevUnity

com.unity.render-pipelines.high-definition/Runtime/Lighting/ProbeVolume/DynamicGI/ProbePropagationAxes.compute

@@ -427,8 +427,7 @@ void PropagateLight(uint3 id : SV_DispatchThreadID)
         _RadianceCacheAxis[index] = EncodeRadiance(radiance);
 
 #ifndef DIRTY_FLAGS_DISABLED
-        float3 previousRadiance = DecodeRadiance(GetPreviousAxisRadiance(index));
-        if (any(abs(radiance - previousRadiance) > 1.0 / 255.0))
+        if (!IsSimilarEqual(GetPreviousAxisRadiance(index), radiance))
         {
             for (int l = 0; l < PROPAGATION_AXIS_AMOUNT; ++l)
             {

com.unity.render-pipelines.high-definition/Runtime/Lighting/ProbeVolume/DynamicGI/ProbePropagationHits.compute

@@ -236,9 +236,7 @@ void AccumulateLightingDirectional(uint3 id : SV_DispatchThreadID)
         lighting += UnpackEmission(neighborData.mixedLighting) * _MixedLightingMultiplier;
 
 #ifndef DIRTY_FLAGS_DISABLED
-        float3 oldLighting = DecodeRadiance(_HitRadianceCacheAxis[hitAxisIndex]);
-
-        if (any(abs(lighting - oldLighting) > 1.0 / 255.0))
+        if (!IsSimilarEqual(_HitRadianceCacheAxis[hitAxisIndex], lighting))
             SetProbeDirty(_ProbeVolumeDirtyFlags, probeIndex);
 #endif
 

com.unity.render-pipelines.high-definition/Runtime/Lighting/ProbeVolume/DynamicGI/ProbeVolumeDynamicGI.cs

@@ -1279,6 +1279,7 @@ internal void DispatchPropagationOutputDynamicSH(
 
             CoreUtils.SetKeyword(cmd, "PROBE_VOLUMES_ENCODING_SPHERICAL_HARMONICS_L1", false);
             CoreUtils.SetKeyword(cmd, "PROBE_VOLUMES_ENCODING_SPHERICAL_HARMONICS_L2", true);
+            CoreUtils.SetKeyword(shader, "DIRTY_FLAGS_DISABLED", true);
 
             cmd.SetComputeVectorParam(shader, HDShaderIDs._ProbeVolumeResolution, (Vector3)size);
             cmd.SetComputeVectorParam(shader, HDShaderIDs._ProbeVolumeResolutionInverse, new Vector3(
@@ -1568,7 +1569,7 @@ unsafe void PrecomputeAxisCacheLookup(int axisAmount, BasisFunction basisFunctio
                 var hitWeightsGoal = 0f;
                 var propagationWeights = 0f;
                 var propagationWeightsGoal = 0f;
-                for (int sortedAxisIndex = 0; sortedAxisIndex < axisAmount; sortedAxisIndex++)
+                for (int sortedAxisIndex = 0; sortedAxisIndex < s_NeighborAxis.Length; sortedAxisIndex++)
                 {
                     if (sortedAxisIndex < axisAmount)
                     {
@@ -1578,14 +1579,13 @@ unsafe void PrecomputeAxisCacheLookup(int axisAmount, BasisFunction basisFunctio
 
                     hitWeightsGoal += _sortedNeighborAxisLookups[sortedAxisStart + sortedAxisIndex].hitWeight;
                     propagationWeightsGoal += _sortedNeighborAxisLookups[sortedAxisStart + sortedAxisIndex].propagationWeight;
-                    
                 }
                 float hitWeightsNormalization = hitWeightsGoal / hitWeights;
                 float propagationWeightsNormalization = propagationWeightsGoal / propagationWeights;
                 for (int sortedAxisIndex = 0; sortedAxisIndex < axisAmount; sortedAxisIndex++)
                 {
                     _sortedNeighborAxisLookups[sortedAxisStart + sortedAxisIndex].hitWeight *= hitWeightsNormalization;
-                    _sortedNeighborAxisLookups[sortedAxisStart + sortedAxisIndex].propagationWeight /= propagationWeightsNormalization;
+                    _sortedNeighborAxisLookups[sortedAxisStart + sortedAxisIndex].propagationWeight *= propagationWeightsNormalization;
                 }
             }
         }

com.unity.render-pipelines.high-definition/Runtime/Lighting/ProbeVolume/DynamicGI/ProbeVolumeDynamicGI.hlsl

@@ -341,5 +341,28 @@ float3 DecodeRadiance(RADIANCE packedValue)
 #endif
 }
 
+bool IsSimilarEqual(RADIANCE packedA, float3 b)
+{
+#if defined(RADIANCE_ENCODING_LOGLUV)
+    const int3 componentsA = int3(packedA & 255, packedA >> 8 & 255, packedA >> 16);
+
+    const float3 logLuvB = LogluvFromRgb(b);
+    const int3 componentsB = int3(
+        min(255, (uint)round(logLuvB.x * 255)),
+        min(255, (uint)round(logLuvB.y * 255)),
+        min(65535, (uint)round(logLuvB.z * 65535)));
+
+    return all(abs(componentsA - componentsB) < int3(2, 2, 32));
+
+#else
+    // TODO: Add a better comparison for HalfLuv and R11G11B10 if they are needed. They'll be giving a lot of false negatives now.
+
+    const float3 a = DecodeRadiance(packedA);
+
+    // Comparison with NaN always gives false. But if max is 0 then min is also 0.
+    // So we accept NaN from the division as true by flipping the condition twice.
+    return !any(min(a, b) / max(a, b) < 0.99);
+#endif
+}
 
 #endif // endof PROBE_VOLUME_DYNAMIC_GI

com.unity.render-pipelines.high-definition/Runtime/Lighting/ProbeVolume/ProbeVolumeLighting.cs

@@ -401,6 +401,13 @@ void CleanupProbeVolumes()
         {
             DestroyProbeVolumeBuffers();
 
+            if (SupportDynamicGI)
+            {
+                var volumes = ProbeVolumeManager.manager.GetVolumesToRender();
+                foreach (var volume in volumes)
+                    ProbeVolumeDynamicGI.instance.ClearProbePropagation(volume);
+            }
+
         #if UNITY_EDITOR
             UnityEditor.Lightmapping.lightingDataCleared -= OnLightingDataCleared;
         #endif
@@ -1449,7 +1456,7 @@ void RenderProbeVolumeDebugOverlay(in DebugParameters debugParameters, CommandBu
                     {
                         DisplayProbeVolumeAtlas(cmd, debugParameters.probeVolumeOverlayParameters, debugParameters.debugOverlay);
                     }
-                    else if (m_SupportDynamicGI && lightingDebug.probeVolumeDebugMode == ProbeVolumeDebugMode.VisualizeDynamicGIDirtyFlags)
+                    else if (SupportDynamicGI && lightingDebug.probeVolumeDebugMode == ProbeVolumeDebugMode.VisualizeDynamicGIDirtyFlags)
                     {
                         DebugDrawProbeVolumeDirtyFlags(cmd);
                     }