Use Piter's PRNG as the source of seeded randomness

README.md

@@ -13,7 +13,7 @@ Features:
 - Strong minification/compression
 - Prints minified bytes and approximate ETH deploy cost on each reload
 - A robust pseudo-random number generator and hashing function (for `tokenData` seed)
-  - See [PRNG](#prng) for an alternative
+  - The included PRNG is suggested by [@piterpasma](https://twitter.com/piterpasma), and uses an "xorshift128" generator.
 - Some utilities for color, math, random, and vector to get you started
 - Additional function analysis, listing the byte size of the largest functions after minification
 - Reports syntax errors in the browser
@@ -69,35 +69,6 @@ You can also `npm install [some-module]` and then `import { foo } from 'some-mod
 
 See [./docs/tips.md](./docs/tips.md) for a series of suggestions on how to reduce bundle size.
 
-## PRNG
-
-The hash function and psuedo-random number generator included in `src/` is fairly strong, and may be overkill for most ArtBlocks scripts. It uses MurmurHash to turn the `tokenData` bytes into an initial state for a permuted congruential generator (PCG).
-
-The following suggestion by [@piterpasma](https://twitter.com/piterpasma), which uses "xorshift128" generator, may be more than sufficient for most applications and can be compressed to a far smaller output:
-
-```js
-// hash from ArtBlocks scripts
-const hash = /* string from tokenData */;
-
-// state of the PRNG
-const xs_state = Uint32Array.from([0,0,0,0].map((_,i)=>parseInt(hash.substr(i*8+2,8),16)))
-
-const prng = () => {
-  /* Algorithm "xor128" from p. 5 of Marsaglia, "Xorshift RNGs" */
-  let s, t = xs_state[3];
-  xs_state[3] = xs_state[2];
-  xs_state[2] = xs_state[1];
-  xs_state[1] = s = xs_state[0];
-  t ^= t << 11;
-  t ^= t >>> 8;
-  xs_state[0] = t ^ s ^ (s >>> 19);
-  return xs_state[0] / 0x100000000;
-};
-
-// prints value in range 0..1
-console.log(prng());
-```
-
 ## License
 
 MIT, see [LICENSE.md](http://github.com/mattdesl/tiny-artblocks/blob/master/LICENSE.md) for details.

src/sketch.js

@@ -1,28 +1,23 @@
-import * as random from "./util/random";
+import CreateGenerator from "./util/random";
 import { Lch } from "./util/color";
 
 export default (hash) => {
+  const { range, pick, gaussian } = CreateGenerator(hash);
   // You may want to remove this line for production
   console.log(hash);
 
-  // set the shared PRNG to new seed
-  random.set_seed(hash);
-
-  const colors = [
-    Lch(50, 50, random.range(180, 360)),
-    Lch(100, 70, random.range(0, 180)),
-  ];
-
+  const colors = [Lch(50, 50, range(180, 360)), Lch(100, 70, range(0, 180))];
+
   const background = Lch(95, 0, 0);
 
   const margin = 0.15;
   const shapes = Array(450)
     .fill()
     .map(() => [
-      random.range(margin, 1 - margin),
-      random.range(margin, 1 - margin),
-      Math.abs(random.gaussian(0, 0.01)),
-      random.pick(colors),
+      range(margin, 1 - margin),
+      range(margin, 1 - margin),
+      Math.abs(gaussian(0, 0.01)),
+      pick(colors),
     ]);
 
   const setContext = (context, color) => {