Wonder-Technology/Wonder.js

// Generate a random unsigned int from two unsigned int values, using 16 pairs
// of rounds of the Tiny Encryption Algorithm. See Zafar, Olano, and Curtis,
// "GPU Random Numbers via the Tiny Encryption Algorithm"
uint tea(uint val0, uint val1) {
  uint v0 = val0;
  uint v1 = val1;
  uint s0 = 0;

  for (uint n = 0; n < 16; n++) {
    s0 += 0x9e3779b9;
    v0 += ((v1 << 4) + 0xa341316c) ^ (v1 + s0) ^ ((v1 >> 5) + 0xc8013ea4);
    v1 += ((v0 << 4) + 0xad90777d) ^ (v0 + s0) ^ ((v0 >> 5) + 0x7e95761e);
  }

  return v0;
}

// Generate a random unsigned int in [0, 2^24) given the previous RNG state
// using the Numerical Recipes linear congruential generator
uint lcg(inout uint prev) {
  uint LCG_A = 1664525u;
  uint LCG_C = 1013904223u;
  prev = (LCG_A * prev + LCG_C);
  return prev & 0x00FFFFFF;
}

// Generate a random float in [0, 1) given the previous RNG state
float rnd(inout uint prev) { return (float(lcg(prev)) / float(0x01000000)); }


vec2 randInUnitDisk(inout uint seed) {
  vec2 p = vec2(0);
  do {
    p = 2 * vec2(rnd(seed), rnd(seed)) - 1;
  } while (dot(p, p) >= 1);
  return p;
}