func Accum(op uint32, value float32) {
	C.glowAccum(gpAccum, (C.GLenum)(op), (C.GLfloat)(value))
}
func Accum(op uint32, value float32) {
	C.glowAccum(gpAccum, (C.GLenum)(op), (C.GLfloat)(value))
}
// operate on the accumulation buffer