使用 Three.js 的 MeshSurfaceSampler 在模型表面采样粒子，粒子逐渐出现在模型表面。

new OBJLoader().load(
    FILE_HOST + 'files/model/z2586300277.obj',
    obj => {
        mesh = obj.children[0];
        mesh.material = new THREE.MeshBasicMaterial({ 
            wireframe: true, 
            color: 0xa58fb5, 
            transparent: true, 
            opacity: 0.2 
        });
        scene.add(obj);
        sampler = new MeshSurfaceSampler(mesh).build();
        renderer.setAnimationLoop(render);
    }
);

const vertices = [];
const colors = [];
const sparklesGeometry = new THREE.BufferGeometry();
const sparklesMaterial = new THREE.PointsMaterial({ 
    size: 6, 
    alphaTest: 0.5, 
    map: new THREE.TextureLoader().load(FILE_HOST + `/images/channels/snow.png`), 
    vertexColors: true 
});
const points = new THREE.Points(sparklesGeometry, sparklesMaterial);
scene.add(points);

const tempPosition = new THREE.Vector3();

function render() {
    if (vertices.length < 10000) {
        sampler.sample(tempPosition);
        vertices.push(tempPosition.x, tempPosition.y, tempPosition.z);
        sparklesGeometry.setAttribute("position", new THREE.Float32BufferAttribute(vertices, 3));

        const color = new THREE.Color(0xa58fb5);
        colors.push(color.r, color.g, color.b);
        sparklesGeometry.setAttribute("color", new THREE.Float32BufferAttribute(colors, 3));
    }

    controls.update();
    renderer.render(scene, camera);
}