public override void BindSurface( int attachment, RenderTexture target )
{
/// Check if the render target is in the rendertarget->FBO map
GLESFrameBufferObject fbobj = target[ "FBO" ] as GLESFrameBufferObject;
Utilities.Contract.Requires( fbobj != null );
_fbo.BindSurface( attachment, fbobj.GetSurface( 0 ) );
GLESConfig.GlCheckError( this );
Width = _fbo.Width;
Height = _fbo.Height;
}