public static event UnityAction onBeforeRender

This callback runs as part of the frame loop on VR and non-VR platforms. It's commonly used for VR to sample input with minimal latency before rendering, but you can use it for any work that must run just before a frame is rendered.

Any work performed within this callback increases the latency between sampling input and rendering to the device. Keep the amount of work done in this callback to a minimum.