veloren/world/src/util/random.rs

use super::Sampler;
use vek::*;

pub struct RandomField {
    seed: u32,
}

impl RandomField {
    pub const fn new(seed: u32) -> Self {
        Self { seed }
    }
}

impl Sampler for RandomField {
    type Index = Vec3<i32>;
    type Sample = u32;

    fn get(&self, pos: Self::Index) -> Self::Sample {
        let pos = pos.map(|e| (e * 13 + (1 << 31)) as u32);

        let mut a = self.seed;
        a = (a ^ 61) ^ (a >> 16);
        a = a + (a << 3);
        a = a ^ pos.x;
        a = a ^ (a >> 4);
        a = a * 0x27d4eb2d;
        a = a ^ (a >> 15);
        a = a ^ pos.y;
        a = (a ^ 61) ^ (a >> 16);
        a = a + (a << 3);
        a = a ^ (a >> 4);
        a = a ^ pos.z;
        a = a * 0x27d4eb2d;
        a = a ^ (a >> 15);
        a
    }
}

pub struct RandomPerm {
    seed: u32,
}

impl RandomPerm {
    pub const fn new(seed: u32) -> Self {
        Self { seed }
    }
}

impl Sampler for RandomPerm {
    type Index = u32;
    type Sample = u32;

    fn get(&self, perm: Self::Index) -> Self::Sample {
        let mut a = perm;
        a = (a ^ 61) ^ (a >> 16);
        a = a + (a << 3);
        a = a ^ (a >> 4);
        a = a * 0x27d4eb2d;
        a = a ^ (a >> 15);
        a
    }
}