The Hydra viewer is the default 3D viewer, but you can revert to Nuke’s legacy Viewer in the Viewer node's Properties > 3D > renderer dropdown. Note:The Hydra Viewer is currently only available on Windows and Linux OS.
The Hydra Viewer is more consistent with other applications in your pipeline, such as Katana, Solaris, or USDView, as well as providing output that represents the output from ScanlineRender nodes more accurately. Nuke 13.0 onwards includes a new Hydra 3D viewport, which uses hdStorm as a new renderer. These views are similar to different cameras that you can look though, but they don’t appear as objects that you can manipulate in the scene. When you do not have a Camera node in your script, the 3D Viewer uses default views (see the figure below for the list of options).
The 2D mode shows the result of a rendered scene, the 3D mode shows the perspective from cameras in the scene. When you have a 3D setup in your script, any Viewer window can toggle between the 2D and 3D display modes.
