small improvement to xoroshiro64

Author: cieplypolar

apps/typegpu-docs/tests/individual-example-tests/uniformity.test.ts

@@ -200,10 +200,21 @@ describe('uniformity test example', () => {
 
       @group(0) @binding(0) var<uniform> configUniform: Config;
 
+      fn hash(v: u32) -> u32 {
+        var x = (v ^ (v >> 17u));
+        x *= 3982152891u;
+        x ^= (x >> 11u);
+        x *= 2890668881u;
+        x ^= (x >> 15u);
+        x *= 830770091u;
+        x ^= (x >> 14u);
+        return x;
+      }
+
       var<private> seed: vec2u;
 
       fn seed2(value: vec2f) {
-        seed = vec2u(value);
+        seed = vec2u(hash(u32(value.x)), hash(u32(value.y)));
       }
 
       fn randSeed2(seed: vec2f) {
@@ -218,12 +229,13 @@ describe('uniformity test example', () => {
         return ((x << k) | (x >> (32u - k)));
       }
 
-      fn next() {
+      fn next() -> u32 {
         let s0 = seed[0i];
         var s1 = seed[1i];
         s1 ^= s0;
         seed[0i] = ((rotl(s0, 26u) ^ s1) ^ (s1 << 9u));
         seed[1i] = rotl(s1, 13u);
+        return (rotl((seed[0i] * 2654435771u), 5u) * 5u);
       }
 
       fn u32To01Float(value: u32) -> f32 {
@@ -234,8 +246,7 @@ describe('uniformity test example', () => {
       }
 
       fn sample() -> f32 {
-        next();
-        let r = seed.x;
+        let r = next();
         return u32To01Float(r);
       }
 

packages/typegpu-noise/src/generator.ts

@@ -63,24 +63,26 @@ export const XOROSHIRO64STARSTAR: StatefulGenerator = (() => {
     return (x << k) | (x >> (32 - k));
   });
 
-  const next = tgpu.fn([])(() => {
+  const next = tgpu.fn(
+    [],
+    d.u32,
+  )(() => {
     const s0 = seed.$[0];
     let s1 = seed.$[1];
-
     s1 ^= s0;
     seed.$[0] = rotl(s0, 26) ^ s1 ^ (s1 << 9);
     seed.$[1] = rotl(s1, 13);
+    return rotl(seed.$[0] * 0x9e3779bb, 5) * 5;
   });
 
   return {
     seed2: tgpu.fn([d.vec2f])((value) => {
-      seed.$ = d.vec2u(value);
+      seed.$ = d.vec2u(hash(d.u32(value.x)), hash(d.u32(value.y)));
     }),
 
     sample: randomGeneratorShell(() => {
       'use gpu';
-      next();
-      const r = seed.$.x;
+      const r = next();
       return u32To01Float(r);
     }).$name('sample'),
   };