Feat sdf loader

[jakekinchen]

What

Adds native support for MDL Molfile / SDF data to three.js via an enhanced SDFLoader.

• The loader now contains a compact inline parser (≈60 LOC) that converts raw SDF text into atom + bond data and then builds the usual instanced-mesh THREE.Group.
• No external Python/PDB conversion required — molecules can be loaded directly in the browser or Node.

Why

Many chemistry / materials projects store molecules as SDF.
Until now developers had to:

1. Convert SDF → PDB with a Python tool, or
2. Write a custom parser.

This PR removes that barrier and lets pure-JS (Next.js, Vite, etc.) apps visualise SDF files out-of-the-box, just like PDB files.

Highlights

• Loader only – the parser lives inside SDFLoader.js; no new export or dependency added to the Addons bundle.
• Robust parsing – tolerates ChemDraw-style files where the counts line over-states bond lines, skips malformed records gracefully.
• Unit-tested – existing SDFLoader.tests.js updated; all addon tests pass.
• Example updated – examples/webgl_loader_sdf.html demonstrates direct SDF loading with atom labels.
• Bundle impact – +≈2 KB (minified) for the inline parser.

Usage

import { SDFLoader } from 'three/addons/loaders/SDFLoader.js';

const loader = new SDFLoader();
loader.load( 'models/sdf/caffeine.sdf', group => scene.add( group ) );

Screenshots

Caffeine rendered from SDF

Implementation Notes

• Parser is wrapped in an IIFE within parse() to keep scope local and avoid public API surface increase.
• ESLint padded-block warnings are disabled only inside that IIFE (loader file stays otherwise lint-clean).
• Element colour / radius tables and instanced-mesh logic remain unchanged and customisable via setElementData().

Happy to adjust naming, structure or docs as requested by maintainers — thanks for reviewing!

[Mugen87]

As suggested at the forum, I vote to move this bit out of the library into a separate repository:

https://discourse.threejs.org/t/why-is-there-a-pdb-loader-and-no-sdf-loader/82861/2

You are ignoring many SDF properties right now that might be relevant for other use cases in the future.

[Mugen87]

I vote to remove SDFLoader and implement the JSON parsing right in the example. The loader contains too much application specific code.

[Mugen87]

The SDF parsing library could be imported like in other examples:

three.js/examples/webgl_loader_ifc.html

Lines 26 to 28 in c6e73de

	"three-mesh-bvh": "https://cdn.jsdelivr.net/npm/[email protected]/build/index.module.js",
	"web-ifc": "https://cdn.jsdelivr.net/npm/[email protected]/web-ifc-api.js",
	"web-ifc-three": "https://cdn.jsdelivr.net/npm/[email protected]/IFCLoader.js"

[WestLangley]

New example: https://raw.githack.com/jakekinchen/three.js/feat-sdf-loader/examples/webgl_loader_sdf.html

Tip: Metals require an environment map. I'd suggest removing the lights and adding RoomEnvironment as your light source.