HnMaterial: improved logic to detect if SRB needs to be recreated

Author: TheMostDiligent

Hydrogent/include/HnTextureRegistry.hpp

@@ -160,12 +160,13 @@ class HnTextureRegistry final : public std::enable_shared_from_this<HnTextureReg
 
     /// Returns the texture registry storage version.
     ///
-    /// \remarks    The storage version is incremented every time a new texture is created
-    ///             or dynamic texture atlas version changes.
+    /// \remarks    The storage version is incremented every time a new texture is created.
     ///
     ///             The storage version is not incremented when the texture data is updated.
     Uint32 GetStorageVersion() const;
 
+    Uint32 GetAtlasVersion() const;
+
     /// Returns the texture registry data version.
     ///
     /// \remarks    The data version is incremented every time a texture is loaded or updated.

Hydrogent/src/HnMaterial.cpp

@@ -975,7 +975,20 @@ bool HnMaterial::UpdateSRB(HnRenderDelegate& RenderDelegate)
     RefCntAutoPtr<HnMaterialSRBCache> SRBCache{RenderDelegate.GetMaterialSRBCache(), IID_HnMaterialSRBCache};
     VERIFY_EXPR(SRBCache);
 
-    const Uint32 ResourceCacheVersion = TexRegistry.GetStorageVersion() + SRBCache->GetMaterialAttribsBufferVersion();
+    const HN_MATERIAL_TEXTURES_BINDING_MODE BindingMode = static_cast<const HnRenderParam*>(RenderDelegate.GetRenderParam())->GetTextureBindingMode();
+
+    Uint32 ResourceCacheVersion = SRBCache->GetMaterialAttribsBufferVersion();
+    if (BindingMode == HN_MATERIAL_TEXTURES_BINDING_MODE_ATLAS)
+    {
+        // Need to recreate SRBs if the atlas texture has changed
+        ResourceCacheVersion += TexRegistry.GetAtlasVersion();
+    }
+    else if (BindingMode == HN_MATERIAL_TEXTURES_BINDING_MODE_DYNAMIC)
+    {
+        // Need to recreate the SRB if any new texture is created
+        ResourceCacheVersion += TexRegistry.GetStorageVersion();
+    }
+
     if (m_ResourceCacheVersion != ResourceCacheVersion)
     {
         m_SRB.Release();
@@ -1022,7 +1035,6 @@ bool HnMaterial::UpdateSRB(HnRenderDelegate& RenderDelegate)
 
     HnMaterialSRBCache::ResourceKey SRBKey{m_ResourceCacheVersion};
 
-    const HN_MATERIAL_TEXTURES_BINDING_MODE BindingMode = static_cast<const HnRenderParam*>(RenderDelegate.GetRenderParam())->GetTextureBindingMode();
     if (BindingMode == HN_MATERIAL_TEXTURES_BINDING_MODE_LEGACY ||
         BindingMode == HN_MATERIAL_TEXTURES_BINDING_MODE_ATLAS)
     {

Hydrogent/src/HnRenderDelegate.cpp

@@ -738,8 +738,8 @@ void HnRenderDelegate::CommitResources(pxr::HdChangeTracker* tracker)
     }
 
     {
-        // Tex storage version is incremented every time a new texture is created or texture atlas version changes.
-        const Uint32 TexStorageVersion = m_TextureRegistry->GetStorageVersion();
+        // Tex storage version is incremented every time a new texture is created.
+        const Uint32 TexStorageVersion = m_TextureRegistry->GetStorageVersion() + m_TextureRegistry->GetAtlasVersion();
         if (m_MaterialResourcesVersion != m_RenderParam->GetAttribVersion(HnRenderParam::GlobalAttrib::Material) + TexStorageVersion)
         {
             std::lock_guard<std::mutex> Guard{m_MaterialsMtx};

Hydrogent/src/HnTextureRegistry.cpp

@@ -416,10 +416,12 @@ HnTextureRegistry::TextureHandleSharedPtr HnTextureRegistry::Allocate(const HnTe
 
 Uint32 HnTextureRegistry::GetStorageVersion() const
 {
-    Uint32 Version = m_StorageVersion.load();
-    if (m_pResourceManager != nullptr)
-        Version += m_pResourceManager->GetTextureVersion();
-    return Version;
+    return m_StorageVersion.load();
+}
+
+Uint32 HnTextureRegistry::GetAtlasVersion() const
+{
+    return m_pResourceManager != nullptr ? m_pResourceManager->GetTextureVersion() : 0;
 }
 
 Uint32 HnTextureRegistry::GetDataVersion() const