render.OverrideAlphaWriteEnable
Example
Shows how you can use alpha channel with render targets.
render.PushRenderTarget( texture )
render.OverrideAlphaWriteEnable( true, true )
render.ClearDepth()
render.Clear( 0, 0, 0, 0 )
render.OverrideAlphaWriteEnable( false )
render.PopRenderTarget()