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The Viewport has a button in the top left corner for starting/stopping IPR, playblasting, resizing resolution, creating a crop window, quickly changing to the PxrVizualizer Integrator, restarting (for changes that do not trigger an update), or taking a snapshot.
You may toggle a progress bar at the bottom the viewport by right-clicking the IPR button.
Additionally, you may right-click on the camera icon to send a snapshot to the Image Tool ("it") with or without the geometry outlines, we default to an anti-aliased version but can be turned off by deselecting "smooth geometry"
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Alternatively you can specify on and off buttons using: optionVar -iv "renderViewRenderSelectedObj" 0; Where 0 is off and 1 is on.
Playblasting
In the RenderMan Preferences there is now a section to specify controls for playblasting from RenderMan in the viewport.