* As we use the texture coordinate as pixel position to calculate random offset,
* the line should passing through rectangle {(0,0),(0,1),(1,0),(1,1)},
* so make the position parameter with two component values between 0.0 to 1.0
* As we use the texture coordinate as pixel position to calculate random offset,
* the line should passing through rectangle {(0,0),(0,1),(1,0),(1,1)},
* so make the position parameter with two component values between 0.0 to 1.0