useGLTF with multiple Draco models fails to load in iOS

[ffdead]

Problem description:

Multiple DRACOLoader instances are known to cause problems on iOS: mrdoob/three.js#22445

The useGLTF hook seems to be creating a new instance every time the hook is used.

Suggested solution:

Could we cache the DRACOLoader instance as a local variable in the hook and check if it's already defined?

[drcmda]

a workaround would be

const [a, b, c] = useGLTF(['a.glb', 'b.glb', 'c.glb'])
return (
  <>
    <Model {...a} />
    <Model {...b} />
    <Model {...c} />

function Model({ scene, nodes, materials }) {
  ...

ideally drei would cache meshopt and draco. i believe it's already doing that with meshopt. though it was probably solved in three-stdlib.

[ffdead]

Could we add something like this? It seems to do the trick but I'm not quite sure of the implications.

import { Loader } from "three";
// @ts-ignore
import { GLTFLoader, DRACOLoader, MeshoptDecoder } from "three-stdlib";
import { useLoader } from "@react-three/fiber";


// cached instance
let dracoLoader = null;


function extensions(
  useDraco: boolean | string,
  useMeshopt: boolean,
  extendLoader?: (loader: GLTFLoader) => void
) {
  return (loader: Loader) => {
    if (extendLoader) {
      extendLoader(loader as GLTFLoader);
    }
    if (useDraco) {

      
      // check if instance exists
      if (!dracoLoader) {
        dracoLoader = new DRACOLoader();
      }


      dracoLoader.setDecoderPath(
        typeof useDraco === "string"
          ? useDraco
          : "https://www.gstatic.com/draco/versioned/decoders/1.4.0/"
      );
      (loader as GLTFLoader).setDRACOLoader(dracoLoader);
    }
    if (useMeshopt) {
      (loader as GLTFLoader).setMeshoptDecoder(
        typeof MeshoptDecoder === "function" ? MeshoptDecoder() : MeshoptDecoder
      );
    }
  };
}

[drcmda]

yes, that would make sense. you do the honours?

[github-actions]

🎉 This issue has been resolved in version 7.20.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[hengjiUSTC]

I am also getting multiple KTX loaders warning when using useKTX2 hook. Should the patten be allied to other loaders as well?