Hydrogent: minor updates/comments

Author: TheMostDiligent

Hydrogent/interface/HnMaterial.hpp

@@ -192,6 +192,12 @@ class HnMaterial final : public pxr::HdMaterial
 
     PBR_Renderer::PSO_FLAGS m_PSOFlags = PBR_Renderer::PSO_FLAG_NONE;
 
+    // Material attribs data resides in a single buffer shared by all SRBs.
+    //
+    //                 Size
+    // |         |-------------| x x x x |
+    //        Offset            Alignment
+
     // Material attribs shader data size in bytes.
     Uint32 m_PBRMaterialAttribsSize = 0;
 

Hydrogent/src/HnMaterial.cpp

@@ -743,6 +743,8 @@ class HnMaterialSRBCache : public ObjectBase<IObject>
                 m_DirtyRangeEnd   = m_MaterialAttribsData.size();
             }
             pContext->UpdateBuffer(pBuffer, m_DirtyRangeStart, m_DirtyRangeEnd - m_DirtyRangeStart, &m_MaterialAttribsData[m_DirtyRangeStart], RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
+            m_DirtyRangeStart = 0;
+            m_DirtyRangeEnd   = 0;
         }
         return pBuffer;
     }
@@ -775,6 +777,7 @@ class HnMaterialSRBCache : public ObjectBase<IObject>
     Uint32     m_CurrBufferOffset   = 0;
     Uint32     m_RequiredBufferSize = 0;
 
+    // Material attribs data resides in a single buffer shared by all SRBs.
     DynamicBuffer      m_MaterialAttribsBuffer;
     std::vector<Uint8> m_MaterialAttribsData;
     Uint32             m_DirtyRangeStart = 0;

Hydrogent/src/HnRenderPass.cpp

@@ -1158,6 +1158,7 @@ void HnRenderPass::UpdateDrawListItemGPUResources(DrawListItem& ListItem, Render
                "Attribs data size (", ListItem.ShaderAttribsDataSize, ") computed from the PSO flags exceeds the attribs buffer range (",
                ListItem.PrimitiveAttribsBufferRange, ") computed from material PSO flags. The latter is used by HnMaterial to set the buffer range.");
 
+        // Note: some PSOs (e.g. shadow) may not use the full range of the material attribs buffer.
         VERIFY(ListItem.pMaterial->GetPBRMaterialAttribsSize() >= State.USDRenderer.GetPBRMaterialAttribsSize(ListItem.PSOFlags),
                "Material attribs size is smaller than required by the PSO flags");
         VERIFY_EXPR(ListItem.pPSO != nullptr);