prerender

This method is called once per frame, before any layer is rendered. It is to be used to allow to prepare resources or render into a texture for the client or initialize some varaibles and states shared across the tiles. The implementation should not make any assumptions about the GL state (other than that the correct context is active). It may make changes to the state, and is not required to reset values such as the depth mask, stencil mask, and corresponding test flags to their original values.

Parameters