UV Unwrapping - Experimental for PLY and STL models

Resources
, ,
8

Save this as three-unwrap.js

import *as XAtlas from "https://esm.sh/xatlas-web@0.1.0"
import *as THREE from "three"

// Modified version of UVUnwrapper: https://github.com/gkjohnson/three-gpu-pathtracer/blob/6e5a452bb1ecb2853dbaa6d5a57682b814df504c/src/utils/UVUnwrapper.js
// Using xatlas-web: https://github.com/mozillareality/xatlas-web

const AddMeshStatus = {
    Success: 0,
    Error: 1,
    IndexOutOfRange: 2,
    InvalidIndexCount: 3
};

export class UVUnwrapper {
    constructor() {
        this._module = null;
    }

    async load() {
        const wasmurl = new URL('https://cdn.jsdelivr.net/npm/xatlas-web@0.1.0/dist/xatlas-web.wasm',import.meta.url);

        this._module = XAtlas['default']({
            locateFile(path) {
                if (path.endsWith('.wasm')) {
                    return wasmurl.toString();
                }

                return path;
            }
        });

        return this._module.ready;
    }

    generate(geometry) {
        const xatlas = this._module;
        const originalVertexCount = geometry.attributes.position.count;
        const originalIndexCount = geometry.index.count;

        xatlas.createAtlas();

        const meshInfo = xatlas.createMesh(originalVertexCount, originalIndexCount, true, true);
        xatlas.HEAPU16.set(geometry.index.array, meshInfo.indexOffset / Uint16Array.BYTES_PER_ELEMENT);
        xatlas.HEAPF32.set(geometry.attributes.position.array, meshInfo.positionOffset / Float32Array.BYTES_PER_ELEMENT);
        xatlas.HEAPF32.set(geometry.attributes.normal.array, meshInfo.normalOffset / Float32Array.BYTES_PER_ELEMENT);

        const statusCode = xatlas.addMesh();

        if (statusCode !== AddMeshStatus.Success) {
            throw new Error(`UVUnwrapper: Error adding mesh. Status code ${statusCode}`);
        }

        xatlas.generateAtlas();

        const meshData = xatlas.getMeshData(meshInfo.meshId);
        const oldPositionArray = geometry.attributes.position.array;
        const oldNormalArray = geometry.attributes.normal.array;

        const newPositionArray = new Float32Array(meshData.newVertexCount * 3);
        const newNormalArray = new Float32Array(meshData.newVertexCount * 3);
        const newUvArray = new Float32Array(xatlas.HEAPF32.buffer,meshData.uvOffset,meshData.newVertexCount * 2);
        const newIndexArray = new Uint32Array(xatlas.HEAPU32.buffer,meshData.indexOffset,meshData.newIndexCount);
        const originalIndexArray = new Uint32Array(xatlas.HEAPU32.buffer,meshData.originalIndexOffset,meshData.newVertexCount);

        for (let i = 0; i < meshData.newVertexCount; i++) {
            const originalIndex = originalIndexArray[i];
            newPositionArray[i * 3] = oldPositionArray[originalIndex * 3];
            newPositionArray[i * 3 + 1] = oldPositionArray[originalIndex * 3 + 1];
            newPositionArray[i * 3 + 2] = oldPositionArray[originalIndex * 3 + 2];
            newNormalArray[i * 3] = oldNormalArray[originalIndex * 3];
            newNormalArray[i * 3 + 1] = oldNormalArray[originalIndex * 3 + 1];
            newNormalArray[i * 3 + 2] = oldNormalArray[originalIndex * 3 + 2];
        }

        geometry.deleteAttribute('position');
        geometry.deleteAttribute('normal');

        geometry.setAttribute('position', new THREE.Float32BufferAttribute(newPositionArray,3));
        geometry.setAttribute('normal', new THREE.Float32BufferAttribute(newNormalArray,3));
        
        geometry.setAttribute('uv', new THREE.Float32BufferAttribute(newUvArray,2));
        geometry.setIndex(new THREE.Uint32BufferAttribute(newIndexArray,1));

        xatlas.destroyAtlas();
    }
}

To test it on a sphere:

import {UVUnwrapper} from "./three-unwrap.js"
let unwrapper = new UVUnwrapper();
await unwrapper.load();
let sphere = new THREE.SphereGeometry();
unwrapper.generate(sphere);
scene.add(new THREE.Mesh(sphere,new THREE.MeshBasicMaterial({wireframe:true,color:"#101020"})))

To visualize the UV map:

let generateUVMesh = ()=>{
    let uvGeom = sphere.clone();
    let v = uvGeom.attributes.position
    let uv = uvGeom.attributes.uv
    for(let i=0;i<v.count;i++){
        let x = uv.getX(i)
        let y = uv.getY(i)
        v.setX(i,x)
        v.setY(i,y)
        v.setZ(i,0);
    }
    let m = new THREE.Mesh(uvGeom,new THREE.MeshBasicMaterial({wireframe:true,color:"#051005"}))
    m.position.y = 10;
    m.scale.multiplyScalar(10)
    scene.add(m)
}
generateUVMesh();
5 Likes