What is a Hydra Render Delegate?

Hydra Render Delegates are bridges between the Hydra viewport and a renderer. They were created by Pixar as part of the Hydra renderer used in usdview. The Hydra Render Delegate system allows the ability to switch out the backend renderer for the viewport data in Hydra.

Render Delegates usually have a name starting with Hd (The Hydra Framework), and two Hydra Render Delegates ship with USD: HdStorm and HdEmbree.

HdStorm is the OpenGL-based renderer that Katana uses by default, which is named GL in the Render Delegates section of the Viewer tab’s Display menu.