fn main() {
	println!("{}", noise(3.14, 42.0, 7.0));
}

fn noise(x: f64, y: f64, z: f64) -> f64 {
	let x0 = x.floor() as usize & 255;
	let y0 = y.floor() as usize & 255;
	let z0 = z.floor() as usize & 255;

	let x = x - x.floor();
	let y = y - y.floor();
	let z = z - z.floor();

	let u = fade(x);
	let v = fade(y);
	let w = fade(z);

	let a = P[x0] + y0;
	let aa = P[a] + z0;
	let ab = P[a + 1] + z0;
	let b = P[x0 + 1] + y0;
	let ba = P[b] + z0;
	let bb = P[b + 1] + z0;

	return lerp(w,
		lerp(v, lerp(u, grad(P[aa], x    , y    , z),
				grad(P[ba], x-1.0, y    , z)),
			lerp(u, grad(P[ab], x    , y-1.0, z),
                                grad(P[bb], x-1.0, y-1.0, z))),
		lerp(v, lerp(u, grad(P[aa+1], x    , y    , z-1.0),
                                grad(P[ba+1], x-1.0, y    , z-1.0)),
                        lerp(u, grad(P[ab+1], x    , y-1.0, z-1.0),
                                grad(P[bb+1], x-1.0, y-1.0, z-1.0))));
}

fn fade(t: f64) -> f64 {
	t * t * t * ( t * (t * 6.0 - 15.0) + 10.0)
}

fn lerp(t: f64, a: f64, b: f64) -> f64 {
	a + t * (b - a)
}

fn grad(hash: usize, x: f64, y: f64, z: f64) -> f64 {
	let h = hash & 15;
	let u = if h < 8 { x } else { y };
	let v = if h < 4 { y } else { if h == 12 || h == 14 { x } else { z } };

	return if h&1 == 0 { u } else { -u } + if h&2 == 0 { v } else { -v };
}

static P: [usize; 512] = [151,160,137,91,90,15,131,13,201,95,96,53,194,233,
	7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,190, 6,148,247,120,234,
	75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,88,237,149,56,87,
	174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,77,146,158,
	231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,102,
	143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
	135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,
	123,5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,
	28,42,223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167,
	43,172,9,129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,
	246,97,228,251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,
	14,239,107,49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127,
	4,150,254,138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,
	180,151,160,137,91,90,15,131,13,201,95,96,53,194,233,7,225,140,36,103,30,69
	,142,8,99,37,240,21,10,23,190, 6,148,247,120,234,75,0,26,197,62,94,252,219,
	203,117,35,11,32,57,177,33,88,237,149,56,87,174,20,125,136,171,168, 68,175,
	74,165,71,134,139,48,27,166, 77,146,158,231,83,111,229,122,60,211,133,230,
	220,105,92,41,55,46,245,40,244,102,143,54, 65,25,63,161, 1,216,80,73,209,
	76,132,187,208, 89,18,169,200,196,135,130,116,188,159,86,164,100,109,198,
	173,186, 3,64,52,217,226,250,124,123,5,202,38,147,118,126,255,82,85,212,
	207,206,59,227,47,16,58,17,182,189,28,42,223,183,170,213,119,248,152, 2,
	44,154,163, 70,221,153,101,155,167, 43,172,9,129,22,39,253, 19,98,108,
	110,79,113,224,232,178,185, 112,104,218,246,97,228,251,34,242,193,238,
	210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107, 49,192,214, 31,
	181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,138,236,205,
	93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180];