high quality deterministic PRNG in WebGPU & WGSL (xorshift128) - MIT licensed

random.wgsl

// each pixel is assigned 4 random u32 values per frame
@group(0) @binding(1)
var<storage, read> rnd_state: array<u32>;

// the current state within this pixel
var<private> local_rnd_state:vec4u;

fn random_u32(state:ptr<private,vec4u>) -> u32 {
  var st:vec4u = *state;
  /* Algorithm "xor128" from p. 5 of Marsaglia, "Xorshift RNGs" */
  // Load the state from the storage buffer
  var t: u32 = st.w;
  var s: u32 = st.x;
  t ^= t << 11;
  t ^= t >> 8;
  var x:u32 = t ^ s ^ (s >> 19);
  *state = vec4u(
    x, s, st.y, st.z
  );
  return x;
}

fn random() -> f32 {
  return f32(random_u32(&local_rnd_state)) / 0x100000000;
}

fn my_main () {
  var idx:u32 = /* index of this pixel into your rnd_state buffer */;

  // each pixel is assigned its own set of 4 random u32 for xorshift
  // then this is stored in a local private space, so that each time
  // random() is called, state will be shifted forward with xorshift
  local_rnd_state = vec4u(
    rnd_state[idx * 4 + 0],
    rnd_state[idx * 4 + 1],
    rnd_state[idx * 4 + 2],
    rnd_state[idx * 4 + 3]
  );
  
  // now you are ready to call random() as many times as you like!
  out_color = vec4(
    random(),
    random(),
    random(),
    1.0
  );
}