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perlin.zig
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pub fn noise(x: f64, y: f64, z: f64) f64 {
const x_int = @intCast(usize, @floatToInt(isize, @floor(x)) & 255);
const y_int = @intCast(usize, @floatToInt(isize, @floor(y)) & 255);
const z_int = @intCast(usize, @floatToInt(isize, @floor(z)) & 255);
const x_float = x - @floor(x);
const y_float = y - @floor(y);
const z_float = z - @floor(z);
const u = fade(x_float);
const v = fade(y_float);
const w = fade(z_float);
const a = permutation[x_int] + y_int;
const aa = permutation[a] + z_int;
const ab = permutation[a+1] + z_int;
const b = permutation[x_int+1] + y_int;
const ba = permutation[b] + z_int;
const bb = permutation[b+1] + z_int;
return lerp(w, lerp(v, lerp(u, grad(permutation[aa], x_float, y_float, z_float),
grad(permutation[ba], x_float-1, y_float, z_float)),
lerp(u, grad(permutation[ab], x_float, y_float-1, z_float),
grad(permutation[bb], x_float-1, y_float-1, z_float))),
lerp(v, lerp(u, grad(permutation[aa+1], x_float, y_float, z_float-1),
grad(permutation[ba+1], x_float-1, y_float, z_float-1)),
lerp(u, grad(permutation[ab+1], x_float, y_float-1, z_float-1),
grad(permutation[bb+1], x_float-1, y_float-1, z_float-1))));
}
pub fn pnoise(x: f64, y: f64, seed: u32) f64 {
return noise(x, y, @intToFloat(f64, seed));
}
pub fn onoise(octaves: usize, x: f64, y: f64, seed: u32) f64 {
var sum : f64 = 0;
var amp : f64 = 1;
var freq : f64 = 1.3;
var i : usize = 0;
while(i < octaves) : (i += 1) {
sum += pnoise(x * freq, y * freq, seed) * amp;
amp *= 2;
freq /= 2;
}
return sum;
}
fn lerp(t: f64, a: f64, b: f64) f64 {
return a + t * (b - a);
}
fn fade(t: f64) f64 {
return t * t * t * (t * (t * 6 - 15) + 10);
}
export fn grad(h: usize, x: f64, y: f64, z: f64) f64 {
switch (h & 15) {
0, 12 => { return x + y; },
1, 14 => { return y - x; },
2 => { return x - y; },
3 => { return -x - y; },
4 => { return x + z; },
5 => { return z - x; },
6 => { return x - z; },
7 => { return -x - z; },
8 => { return y + z; },
9, 13 => { return z - y; },
10 => { return y - z; },
else => { return -y - z; }, // 11, 16
}
}
const permutation = [_]usize{
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,
};