code: func ClearAccum(red float32, green float32, blue float32, alpha float32) {
  	syscall.Syscall6(gpClearAccum, 4, uintptr(math.Float32bits(red)), uintptr(math.Float32bits(green)), uintptr(math.Float32bits(blue)), uintptr(math.Float32bits(alpha)), 0, 0)
  }
docs: // specify clear values for the accumulation buffer