Design intent behind HdRenderSettingsMap, HdRenderSettingsSchema, and UsdRenderSpec

ppt-adsk · March 25, 2025, 4:00pm

Hello Hydra friends,

I’m trying to understand the architectural relationship between the aforementioned classes.

HdRenderSettingsMap is just a typedef on a TfToken to VtValue map

github.com/PixarAnimationStudios/OpenUSD

pxr/imaging/hd/renderDelegate.h

319925ecc


      
              /// Since this method can be called by client code, it must be thread-safe.
              HD_API
              virtual bool HasArbitraryValue(const TfToken& key) const;
          
          private:
              // Hydra will not attempt to copy the class.
              HdRenderParam(const HdRenderParam &) = delete;
              HdRenderParam &operator =(const HdRenderParam &) = delete;
          };
          
          typedef TfHashMap<TfToken, VtValue, TfToken::HashFunctor> HdRenderSettingsMap;
          
          ///
          /// HdRenderSettingDescriptor represents a render setting that a render delegate
          /// wants to export (e.g. to UI).
          ///
          struct HdRenderSettingDescriptor 
          {
              // A human readable name.
              std::string name;
              // The key for HdRenderDelegate::SetRenderSetting/GetRenderSetting.

It is importantly passed in to the HdRenderDelegate constructor:

github.com/PixarAnimationStudios/OpenUSD

pxr/imaging/hd/renderDelegate.h

319925ecc


      
              /// specified prim type.
              HD_API
              virtual bool IsParallelSyncEnabled(const TfToken &primType) const;
          
          protected:
              /// This class must be derived from.
              HD_API
              HdRenderDelegate();
              /// Allow derived classes to pass construction-time render settings.
              HD_API
              HdRenderDelegate(HdRenderSettingsMap const& settingsMap);
          
              ///
              /// This class is not intended to be copied.
              ///
              HdRenderDelegate(const HdRenderDelegate &) = delete;
              HdRenderDelegate &operator=(const HdRenderDelegate &) = delete;
          
              HD_API
              void _PopulateDefaultSettings(
                  HdRenderSettingDescriptorList const& defaultSettings);

How is this map created?

HdRenderSettingsSchema:

seems to describe the Hydra view of render settings. On which prim(s) is this schema expected to be available?

UsdRenderSpec (preliminary API, stated in the documentation as likely to change):

Seems to be intended as a boiled-down version of Usd render settings, but I am unclear as to the link between this and Hydra render settings.

Any help or links to existing documentation are appreciated. Thanks!

Pierre

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Design intent behind HdRenderSettingsMap, HdRenderSettingsSchema, and UsdRenderSpec

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