The viewport determines the region and depth range of the framebuffer that the RenderPass draws to.

Allow the user to set the viewport on the RenderPass by passing in a Viewport class containing a floating point region rectangle and a floating point DepthRange (defaulting to zNear=0 and zFar=1).

Similar to the scissor, there is no need to add functionality to "disable" the viewport. By default, the viewport's region is set to the render target texture size and the viewport's depth range is set to zNear=0 and zFar=1. So if the user wants to "disable" the viewport, they should simply call setViewport again and set it back to the default values.