* @param[in] offscreenId A resource Id of an off-screen render target, or 0
* @param[in] viewport A pointer to a viewport, of NULL.
* @param[in] clearColor A pointer to a color to clear with, or NULL if no clear is required.
*/
* @param[in] offscreenId A resource Id of an off-screen render target, or 0
* @param[in] viewport A pointer to a viewport, of NULL.
* @param[in] clearColor A pointer to a color to clear with, or NULL if no clear is required.
*/