WebGL/WebGL2: any integer-valued number ≥ 1e21 emits invalid GLSL (`1e+30.0`)

[fuzzie360]

Summary

On the WebGL and WebGL2 backends, an integer-valued number of 1e21 or larger produces a fragment shader that fails to compile:

Error compiling fragment shader: ERROR: 0:518: '.0' : syntax error

The generated GLSL contains 1e+30.0, which is not a valid float literal.

1e30 is a natural thing to write — it is the usual "infinitely far away" sentinel in a ray marcher or path tracer, which is where I hit it.

Reproduction

Verified on gpu.js 2.21.0, Chrome 150, Apple M1 Max (apple metal-3), via dist/gpu-browser.js.

// FAILS — literal in the kernel body
new GPU({ mode: 'webgl2' })
  .createKernel(function () { return 1e30; })
  .setOutput([1])();

// FAILS — value passed through setConstants
new GPU({ mode: 'webgl2' })
  .createKernel(function () { return this.constants.big * 1; })
  .setConstants({ big: 1e30 })
  .setOutput([1])();

// OK — runtime argument, uploaded as a uniform rather than emitted into source
new GPU({ mode: 'webgl2' })
  .createKernel(function (v) { return v * 1; })
  .setOutput([1])(1e30);

Affected backends

backend	1e30	1e21	1e20	123456
webgl2	FAIL	FAIL	ok	ok
webgl	FAIL	FAIL	ok	ok
webgpu	ok	ok	ok	ok

Cause

The threshold is exactly 1e21, which is where Number.prototype.toString() switches to exponential notation:

(1e20).toString()  // "100000000000000000000"  -> "100000000000000000000.0"  valid
(1e21).toString()  // "1e+21"                  -> "1e+21.0"                  invalid

src/backend/web-gl/function-node.js (around line 237) appends .0 whenever the value is an integer:

if (Number.isInteger(ast.value)) {
  ...
  retArr.push(`${ast.value}.0`);

Number.isInteger(1e30) is true, so the .0 is appended to a string that is already in exponential form.

Suggested fix

Only append .0 when the rendered string does not already make the literal a float. GLSL accepts 1e30 as a float literal, so the exponential form can pass through unchanged:

const s = `${ast.value}`;
retArr.push(/[.eE]/.test(s) ? s : `${s}.0`);

The same ${value}.0 pattern appears in src/backend/function-node.js and src/backend/web-gpu/function-node.js; I only observed the failure on the two WebGL backends, so I have not checked whether the others are reachable with the same input.

Workaround

Keep sentinels below 1e21 — 1e20 renders as digits and works, and for most scenes something like 1e9 is plenty.