Lut

// initialize lut
val lut = Lut()
for (r in 0..15) {
    for (g in 0..15) {
        for (b in 0..15) {
            // set a mapping color for each RGB value in the (0-15)^3 range
            lut.setMapping(r, g, b, r * 4 + r / 4, g * 4 + g / 4, b * 4 + b / 4)
        }
    }
}

// alternatively, for a simple scaling, you can use `Lut.fromScale(Vector3)`
val lut = Lut.fromScale(Vector3(0.25f))

// loading from a bitmap is possible too
val lut = Lut.fromBitmap(BitmapFactory.decodeFile("lut.png"))

// finally, apply it to the passthrough
scene.setPassthroughLUT(lut)