func SampleCoverage(value float32, invert bool) {
	syscall.Syscall(gpSampleCoverage, 2, uintptr(math.Float32bits(value)), boolToUintptr(invert), 0)
}
func SampleCoverage(value float32, invert bool) {
	syscall.Syscall(gpSampleCoverage, 2, uintptr(math.Float32bits(value)), boolToUintptr(invert), 0)
}
func SampleCoverage ( value float32 , invert bool ) { syscall . Syscall ( gpSampleCoverage , 2 , uintptr ( math . Float32bits ( value ) ) , boolToUintptr ( invert ) , 0 ) }
// specify multisample coverage parameters
specify multisample coverage parameters