gistfile1.txt

struct Vec2 {
    x: f32,
    y: f32,
}

#[inline(always)]
fn lerp(a: f32, b: f32, v: f32) -> f32 {
    a * (1f32 - v) + b * v
}

#[inline(always)]
fn smooth(v: f32) -> f32 {
    v * v * (3f32 - 2f32 * v)
}

#[inline(always)]
fn random_gradient(r: rand::Rng) -> Vec2 {
    let v = r.gen_float() * float::consts::pi * 2.0;
    Vec2{
        x: float::cos(v) as f32,
        y: float::sin(v) as f32,
    }
}

#[inline(always)]
fn gradient(orig: Vec2, grad: Vec2, p: Vec2) -> f32 {
    let sp = Vec2{x: p.x - orig.x, y: p.y - orig.y};
    grad.x * sp.x + grad.y + sp.y
}

struct Noise2DContext {
    rgradients: ~[Vec2],
    permutations: ~[int],
}

#[inline(always)]
fn Noise2DContext() -> ~Noise2DContext {
    let r = rand::Rng();
    let rgradients = do vec::from_fn(256) |_i| { random_gradient(r) };
    let mut permutations = do vec::from_fn(256) |i| { i as int };
    r.shuffle_mut(permutations);

    ~Noise2DContext{
        rgradients: move rgradients,
        permutations: move permutations,
    }
}

impl Noise2DContext {
    #[inline(always)]
    fn get_gradient(x: int, y: int) -> Vec2 {
        let idx = self.permutations[x & 255] + self.permutations[y & 255];
        self.rgradients[idx & 255]
    }

    #[inline(always)]
    fn get_gradients(gradients: &[mut Vec2 * 4], origins: &[mut Vec2 * 4], x: f32, y: f32) {
        let x0f = float::floor(x as libc::c_double) as f32;
        let y0f = float::floor(y as libc::c_double) as f32;
        let x0 = x0f as int;
        let y0 = y0f as int;
        let x1 = x0 + 1;
        let y1 = y0 + 1;

        gradients[0] = self.get_gradient(x0, y0);
        gradients[1] = self.get_gradient(x1, y0);
        gradients[2] = self.get_gradient(x0, y1);
        gradients[3] = self.get_gradient(x1, y1);

        origins[0] = Vec2{x: x0f + 0f32, y: y0f + 0f32};
        origins[1] = Vec2{x: x0f + 1f32, y: y0f + 0f32};
        origins[2] = Vec2{x: x0f + 0f32, y: y0f + 1f32};
        origins[3] = Vec2{x: x0f + 1f32, y: y0f + 1f32};
    }

    #[inline(always)]
    fn get(x: f32, y: f32) -> f32 {
        let p = Vec2{x: x, y: y};
        let gradients: [mut Vec2 * 4] = [mut
            Vec2{x:0f32, y:0f32},
            Vec2{x:0f32, y:0f32},
            Vec2{x:0f32, y:0f32},
            Vec2{x:0f32, y:0f32},
        ];
        let origins: [mut Vec2 * 4] = [mut
            Vec2{x:0f32, y:0f32},
            Vec2{x:0f32, y:0f32},
            Vec2{x:0f32, y:0f32},
            Vec2{x:0f32, y:0f32},
        ];
        self.get_gradients(&gradients, &origins, x, y);
        let v0 = gradient(origins[0], gradients[0], p);
        let v1 = gradient(origins[1], gradients[1], p);
        let v2 = gradient(origins[2], gradients[2], p);
        let v3 = gradient(origins[3], gradients[3], p);
        let fx = smooth(x - origins[0].x);
        let vx0 = lerp(v0, v1, fx);
        let vx1 = lerp(v2, v3, fx);
        let fy = smooth(y - origins[0].y);
        lerp(vx0, vx1, fy)
    }
}

fn main() {
    let symbols = [" ", "░", "▒", "▓", "█", "█"];
    let pixels = vec::to_mut(vec::from_elem(256*256, 0f32));
    let n2d = Noise2DContext();
    for 100.times {
        for int::range(0, 256) |y| {
            for int::range(0, 256) |x| {
                let v = n2d.get(
                    x as f32 * 0.1f32,
                    y as f32 * 0.1f32
                ) * 0.5f32 + 0.5f32;
                pixels[y*256+x] = v;
            };
        };
    };

//    for int::range(0, 256) |y| {
//        for int::range(0, 256) |x| {
//            io::print(symbols[pixels[y*256+x] / 0.2f32 as int]);
//        }
//        io::println("");
//    }
}