OnPreRender is called before a camera starts rendering the scene.
This message is sent to all scripts attached to the camera.
Note that if you change camera's viewing parameters (e.g. fieldOfView) here, they will only take effect the next frame. Do that in OnPreCull instead.
Also note that when OnPreRender is called, the camera's render target is not set up yet, and the depth texture(s) are not rendered yet either. If you want to do something later on (when the render target is already set), try using a CommandBuffer.
See Also: onPreRender delegate.