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const rand = @import("rand.zig");
const Random = rand.Random;
const randomReal01 = rand.randomReal01;
const randomInt = rand.randomInt;
const Point3 = @import("vec.zig").Point3;
pub const Perlin = struct {
const POINT_COUNT = 256;
randomNoise: [POINT_COUNT]f64,
permX: [POINT_COUNT]usize,
permY: [POINT_COUNT]usize,
permZ: [POINT_COUNT]usize,
pub fn init(rng: Random) Perlin {
var perlin = Perlin{
.randomNoise = undefined,
.permX = undefined,
.permY = undefined,
.permZ = undefined,
};
var i: usize = 0;
while (i < POINT_COUNT) : (i += 1) {
perlin.randomNoise[i] = randomReal01(rng);
}
perlinGeneratePerm(rng, &perlin.permX);
perlinGeneratePerm(rng, &perlin.permY);
perlinGeneratePerm(rng, &perlin.permZ);
return perlin;
}
pub fn noise(perlin: Perlin, p: Point3) f64 {
const i = @intCast(usize, @floatToInt(i32, 4.0 * p.x) & 255);
const j = @intCast(usize, @floatToInt(i32, 4.0 * p.y) & 255);
const k = @intCast(usize, @floatToInt(i32, 4.0 * p.z) & 255);
return perlin.randomNoise[perlin.permX[i] ^ perlin.permY[j] ^ perlin.permZ[k]];
}
fn perlinGeneratePerm(rng: Random, p: []usize) void {
var i: usize = 0;
while (i < POINT_COUNT) : (i += 1) {
p[i] = i;
}
permute(rng, p, POINT_COUNT);
}
fn permute(rng: Random, p: []usize, n: usize) void {
var i = n - 1;
while (i > 0) : (i -= 1) {
const target = randomInt(usize, rng, 0, i);
const tmp = p[i];
p[i] = p[target];
p[target] = tmp;
}
}
};
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