gemrenderer

Gemstones, cut the way they're meant to be. Ray-traced in the browser, with no frontend framework required.

gemrenderer is free and MIT licensed. If you find it useful, you can support its development:

gemrenderer renders gemstones by describing them in parts: a body colour, a cut, and a few optical constants. From there it builds the geometry and traces light through each facet. Fresnel reflection, refraction, total internal reflection and exit all come into play, with red, green and blue bending slightly differently to produce real chromatic fire. As light travels inside the stone, Beer–Lambert absorption deepens the colour based on the body colour, refractive index and dispersion.

The library doesn't hardcode any specific gemstone names. Instead, it ships a set of ready-made stones (benitoite, red beryl, musgravite, painite, alexandrite, paraíba, sapphire, emerald, ruby and diamond) as presets in gemrenderer/presets. You can use them as-is, or define your own from scratch.

• Works with or without a framework. There's a vanilla DOM class, plus a small pure-function core and pointer gesture. You can also use it in Vue, React, Svelte or plain HTML/JS.
• Optionally glinting. configure({ glint }) adds a small bloom pass so the facets that catch the studio's hot spots flare softly instead of clipping to hard white. Off by default — no post pass, no cost.
• One WebGL context for the whole page. Stones are baked once per (spec, clarity) and cached. Static images and live spinners share the same meshes, so nothing is wasted.
• Falls back gracefully without WebGL. If the browser can't create a WebGL context, it keeps a placeholder and your layout stays intact.
• No assets, no build step. Everything runs from plain ESM source with a small procedural HDR studio.
• MIT licensed.

rubjo.github.io/gemrenderer — Every preset on display; drag any of them to spin it. Feature a stone, then make it yours: changing its colour or cut (or hitting Randomize) turns the featured stone into a Custom one — the optics knobs on the panel (fire, light paths, glint) belong to the ray-traced path and grey out when the renderer is set to rasterised.

npm install gemrenderer three

three is a peer dependency (>=0.163). Use the version your app already ships. gemrenderer loads three.js lazily, only when it actually needs to render.

import { GemView } from 'gemrenderer'

// Define your own stone: a square-cut deep red brilliant
new GemView('#mount', {
  color: 0xa6001a,
  cut: { family: 'brilliant', poly: 4 },
  ior: 1.77,
  fire: 0.41,
  clarity: 8,
})

// Or use one of the built-in presets
import { gemSpec } from 'gemrenderer/presets'
new GemView('#mount', { ...gemSpec('ruby'), clarity: 8 })

That's it for most use cases. A placeholder appears first, then the baked stone replaces it. Once you drag it, it becomes a live canvas that spins freely in both directions and eases back to its resting position when you let go.

Per-stone looks come from the spec; page-wide knobs — brightness everywhere, plus dispersion, light paths and glint on the ray-traced path — are set once with configure() and re-bake every mounted stone lazily. An individual spec can also pin its own fire, bright, bounces or glint, so one stone gets different optics without touching the others. A design note on the glint pass lives in docs/glint.md.