Represents the area in screen-space that is visible on the XR Display.
The visibility mesh contains vertices outlining the visible area of the XR display in screen-space coordinates. The mesh encompasses both eyes under single-pass instanced rendering and one eye under multi-pass rendering (a different eye for each pass).
When available, the Unity post-processing stack uses the visibility mesh to avoid processing pixels that are outside the visible display area of the XR headset.
You can use this mesh to prevent your screen-space shaders from drawing to areas that are outside the effective display area. For example, if you are performing your own post-processing step, you might be able to optimize it by specifying the screen area in which the post-processing effect should be calculated.
If a device or platform does not provide a visibility mesh, then this XR render parameter field is null.