Hydrogent: fixed rendering of motion vectors for translucent materials with OIT

Author: TheMostDiligent

Hydrogent/src/HnRenderPass.cpp

@@ -1333,6 +1333,11 @@ void HnRenderPass::UpdateDrawListItemGPUResources(DrawListItem& ListItem, Render
             if (Geo.TexCoords[1] != nullptr)
                 PSOFlags |= PBR_Renderer::PSO_FLAG_USE_TEXCOORD1;
 
+            if ((m_Params.UsdPsoFlags & USD_Renderer::USD_PSO_FLAG_ENABLE_MOTION_VECTORS_OUTPUT) != 0)
+            {
+                PSOFlags |= PBR_Renderer::PSO_FLAG_COMPUTE_MOTION_VECTORS;
+            }
+
             if (pMaterial != nullptr)
             {
                 const PBR_Renderer::PSO_FLAGS MaterialPSOFlags = GetMaterialPSOFlags(*pMaterial);
@@ -1343,7 +1348,7 @@ void HnRenderPass::UpdateDrawListItemGPUResources(DrawListItem& ListItem, Render
                 else
                 {
                     // Color map is needed for alpha-masked materials
-                    PSOFlags |= (MaterialPSOFlags & (PBR_Renderer::PSO_FLAG_USE_COLOR_MAP & PBR_Renderer::PSO_FLAG_ENABLE_TEXCOORD_TRANSFORM));
+                    PSOFlags |= (MaterialPSOFlags & (PBR_Renderer::PSO_FLAG_USE_COLOR_MAP | PBR_Renderer::PSO_FLAG_ENABLE_TEXCOORD_TRANSFORM));
                 }
 
                 VERIFY(((m_Params.AlphaMode != USD_Renderer::ALPHA_MODE_NUM_MODES ? m_Params.AlphaMode : pMaterial->GetMaterialData().Attribs.AlphaMode) == State.AlphaMode ||

Hydrogent/src/Tasks/HnTaskManager.cpp

@@ -208,7 +208,11 @@ HnTaskManager::HnTaskManager(pxr::HdRenderIndex& RenderIndex,
     const USD_Renderer& Renderer   = *static_cast<const HnRenderDelegate*>(GetRenderIndex().GetRenderDelegate())->GetUSDRenderer();
     const bool          OITEnabled = Renderer.GetSettings().OITLayerCount > 0;
 
-    USD_Renderer::USD_PSO_FLAGS TranslucentPassOutputs = USD_Renderer::USD_PSO_FLAG_ENABLE_ALL_OUTPUTS;
+    USD_Renderer::USD_PSO_FLAGS           TranslucentPassOutputs = USD_Renderer::USD_PSO_FLAG_ENABLE_ALL_OUTPUTS;
+    constexpr USD_Renderer::USD_PSO_FLAGS TranslucentMeshIdPassOutputs =
+        USD_Renderer::USD_PSO_FLAG_ENABLE_MESH_ID_OUTPUT |
+        USD_Renderer::USD_PSO_FLAG_ENABLE_MOTION_VECTORS_OUTPUT |
+        USD_Renderer::USD_PSO_FLAG_ENABLE_NORMAL_OUTPUT;
     if (OITEnabled)
     {
         CreateBeginOITPassTask();
@@ -222,8 +226,7 @@ HnTaskManager::HnTaskManager(pxr::HdRenderIndex& RenderIndex,
                                });
         CreateEndOITPassTask();
         // We will write mesh ID, motion vectors and depth in a separate pass
-        TranslucentPassOutputs &= ~(USD_Renderer::USD_PSO_FLAG_ENABLE_MESH_ID_OUTPUT |
-                                    USD_Renderer::USD_PSO_FLAG_ENABLE_MOTION_VECTORS_OUTPUT);
+        TranslucentPassOutputs &= ~TranslucentMeshIdPassOutputs;
     }
 
     CreateRenderRprimsTask(HnMaterialTagTokens->translucent,
@@ -244,7 +247,7 @@ HnTaskManager::HnTaskManager(pxr::HdRenderIndex& RenderIndex,
                                    HnRenderResourceTokens->renderPass_TransparentAll,
                                    HnRenderPassParams::SelectionType::All,
                                    USD_Renderer::RenderPassType::Main,
-                                   USD_Renderer::USD_PSO_FLAG_ENABLE_MESH_ID_OUTPUT | USD_Renderer::USD_PSO_FLAG_ENABLE_MOTION_VECTORS_OUTPUT,
+                                   TranslucentMeshIdPassOutputs,
                                    USD_Renderer::ALPHA_MODE_OPAQUE, // Override alpha mode
                                });
     }

PBR/src/USD_Renderer.cpp

@@ -120,7 +120,6 @@ USD_Renderer::CreateInfo::PSMainSourceInfo USD_Renderer::GetUsdPbrPSMainSource(U
 #   endif
 #endif
 
-    Normal       *= Transmittance;
     MaterialData *= Transmittance;
     IBL          *= Transmittance;
 )";

Shaders/PBR/private/RenderPBR.psh

@@ -549,7 +549,6 @@ PSOutput main(in VSOutput VSOut,
                 D = 1.0 - D;
             }
             Transmittance = GetOITTransmittance(D, uint2(VSOut.ClipPos.xy));
-            OutColor.rgb *= Transmittance;
         }
 #endif
     }
@@ -618,6 +617,8 @@ PSOutput main(in VSOutput VSOut,
     }
 #endif
 
+    OutColor.rgb *= Transmittance;
+ 
 #if CONVERT_OUTPUT_TO_SRGB
     {
         OutColor.rgb = FastLinearToSRGB(OutColor.rgb);