Merge branch 'dev/ralston/rtxdi_update' into 'main'

Update RTXDI and Volumetric code

See merge request lightspeedrtx/dxvk-remix-nv!1165

Author: anon-apple

src/dxvk/shaders/rtx/algorithm/volume_integrator.slangh

@@ -238,12 +238,39 @@ void integrateVolume(
   {
     // Construct a new Reservoir via RIS
 
-    // Note: Cached light sample currently used externally, could be used to avoid needing to rederive the light sample in some
-    // cases, but this may just add divergance and not be worth it.
-    RAB_LightSample cachedSelectedLightSample;
-    const VolumeReSTIR_Reservoir newVolumeReservoir = VolumeReSTIR_SampleLightRIS(
-      rabRandomState, rabVolumeVisibilityContext, rabVolumeInteraction,
-      cachedSelectedLightSample, volumeParameters);
+    VolumeReSTIR_Reservoir newVolumeReservoir = VolumeReSTIR_SampleLightRIS(
+      rabRandomState, rabVolumeVisibilityContext, rabVolumeInteraction, volumeParameters);
+
+    // Perform an initial visiblity check
+
+    if (volumeParameters.enableVolumeRISInitialVisibility && newVolumeReservoir.isValid())
+    {
+      // Get the light sample from the reservoir
+
+      RAB_LightSample rabLightSample;
+      float inverseSelectionPdf;
+
+      // Note: Assuming the light sample is always valid here if it was selected to begin with via RIS.
+      VolumeReSTIR_GetLightSample(
+        newVolumeReservoir, rabVolumeInteraction,
+        rabLightSample, inverseSelectionPdf);
+
+      // Test visibility to the light sample for the reservoir
+
+      // Note: Currently set to the invalid Ray Portal index until we support cross-portal lighting here.
+      uint8_t sampledTransportPortalIndex = RTXDI_INVALID_PORTAL_INDEX;
+      float16_t3 attenuation = float16_t3(0.0f);
+      const bool visible = RAB_VolumeReSTIR_TraceNEEVisibility(
+        rabLightSample, sampledTransportPortalIndex,
+        rabVolumeVisibilityContext, rabVolumeInteraction, attenuation);
+
+      // Invalidate the reservoir if the visibility test fails
+
+      if (!visible || all(attenuation == float16_t3(0.0f)))
+      {
+        newVolumeReservoir.invalidate();
+      }
+    }
 
     // Merge the new Reservoir into the current Reservoir
 

src/dxvk/shaders/rtx/pass/volume_args.h

@@ -36,6 +36,11 @@ struct VolumeArgs {
   uint2 froxelGridDimensions;
   vec2 inverseFroxelGridDimensions;
 
+  // Note: These parameters are currently currently unused but present due to being referenced in the also currently unused VolumeReSTIR_SpatialResampling and VolumeReSTIR_TemporalResampling functions.
+  // This comment should be removed once these parameters become properly set and the volume ReSTIR code is put into use. Do not use these parameters until then as they will not be set.
+  uint2 restirFroxelGridDimensions;
+  vec2 restirInverseFroxelGridDimensions;
+
   uint numFroxelVolumes;       // 1 if there is just the main camera volume in the texture, 3 if there are also per-portal volumes
   uint numActiveFroxelVolumes; // Same logic as numFroxelVolumes but only counting active volumes
   uint froxelDepthSlices;