如何在Three.js中获取蒙皮网格的顶点的全局位置？

Question

In Three.js, we are now able to get the global position of a vertex of a non-skinned mesh thanks to this question , but how can I get the global position of a vertex of a skinned mesh with bones and morph targets?

For example, how can I print (2.5, 1.5, 0.5) in the following situation? mesh.geometry.vertices[0] is originally at (0.5, 0.5, 0.5) . Then, bones[1] moves the vertex to (2.5, 0.5, 0.5) . Finally, morphing moves the vertex to (2.5, 1.5, 0.5) .

 const scene = new THREE.Scene(); const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 200); camera.position.z = 3; camera.position.y = 2; camera.lookAt(0, 0, 0); const renderer = new THREE.WebGLRenderer({antialias: true}); renderer.setPixelRatio(window.devicePixelRatio); renderer.setSize(window.innerWidth, window.innerHeight); document.body.appendChild(renderer.domElement); const geometry = new THREE.BoxGeometry(1, 1, 1); geometry.morphTargets.push({name: "morph", vertices: []}); for (const vertex of geometry.vertices) { geometry.skinIndices.push(new THREE.Vector4(vertex.x < 0 ? 0 : 1, 0, 0, 0)); geometry.skinWeights.push(new THREE.Vector4(1, 0, 0, 0)); geometry.morphTargets[0].vertices.push(vertex.clone().add(new THREE.Vector3(0, 1, 0))); } const material = new THREE.MeshPhongMaterial({ skinning: true, emissive: 0xffffff, wireframe: true, morphTargets: true }); const mesh = new THREE.SkinnedMesh(geometry, material); const bones = [new THREE.Bone(), new THREE.Bone()]; for (const bone of bones) { mesh.add(bone); } const skeleton = new THREE.Skeleton(bones); mesh.bind(skeleton); bones[0].position.x = -2; bones[1].position.x = 2; mesh.morphTargetInfluences[0] = 1; scene.add(mesh); // This code assigns (0.5, 0.5, 0.5) to pos, // but I want to know the code which assigns (2.5, 1.5, 0.5) to pos. const pos = mesh.geometry.vertices[0].clone().applyMatrix4(mesh.matrixWorld); console.log(`(${pos.x}, ${pos.y}, ${pos.z})`); (function render() { requestAnimationFrame(render); renderer.render(scene, camera); })(); 

 body { margin: 0; overflow: hidden; } canvas { width: 100%; height: 100%; } 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/94/three.min.js"></script> 

Answer 1

So this is what I did to try to figure this out. I'm too lazy to check if it works for all cases but ...

First I used the Shader Editor extension and then I ran a skinned example and using the shader editor I looked at the generated shader

Looking at the vertex shader the relevant part of the shader is

#ifdef USE_SKINNING
    mat4 boneMatX = getBoneMatrix( skinIndex.x );
    mat4 boneMatY = getBoneMatrix( skinIndex.y );
    mat4 boneMatZ = getBoneMatrix( skinIndex.z );
    mat4 boneMatW = getBoneMatrix( skinIndex.w );
#endif
#ifdef USE_SKINNING
    mat4 skinMatrix = mat4( 0.0 );
    skinMatrix += skinWeight.x * boneMatX;
    skinMatrix += skinWeight.y * boneMatY;
    skinMatrix += skinWeight.z * boneMatZ;
    skinMatrix += skinWeight.w * boneMatW;
    skinMatrix  = bindMatrixInverse * skinMatrix * bindMatrix;
    objectNormal = vec4( skinMatrix * vec4( objectNormal, 0.0 ) ).xyz;
#endif

vec3 transformedNormal = normalMatrix * objectNormal;
#ifdef FLIP_SIDED
    transformedNormal = - transformedNormal;
#endif


vec3 transformed = vec3( position );

#ifdef USE_MORPHTARGETS
    transformed += ( morphTarget0 - position ) * morphTargetInfluences[ 0 ];
    transformed += ( morphTarget1 - position ) * morphTargetInfluences[ 1 ];
    transformed += ( morphTarget2 - position ) * morphTargetInfluences[ 2 ];
    transformed += ( morphTarget3 - position ) * morphTargetInfluences[ 3 ];
    #ifndef USE_MORPHNORMALS
    transformed += ( morphTarget4 - position ) * morphTargetInfluences[ 4 ];
    transformed += ( morphTarget5 - position ) * morphTargetInfluences[ 5 ];
    transformed += ( morphTarget6 - position ) * morphTargetInfluences[ 6 ];
    transformed += ( morphTarget7 - position ) * morphTargetInfluences[ 7 ];
    #endif
#endif

#ifdef USE_SKINNING
    vec4 skinVertex = bindMatrix * vec4( transformed, 1.0 );
    vec4 skinned = vec4( 0.0 );
    skinned += boneMatX * skinVertex * skinWeight.x;
    skinned += boneMatY * skinVertex * skinWeight.y;
    skinned += boneMatZ * skinVertex * skinWeight.z;
    skinned += boneMatW * skinVertex * skinWeight.w;
    transformed = ( bindMatrixInverse * skinned ).xyz;
#endif

So translating that into JavaScript here's what I came up with

First off you need the scene to have all its world matrices and the skeleton updated.

scene.updateMatrixWorld();
skeleton.update();

Then

  // These are so we can avoid doing allocations
  // in the inner loop.
  const position = new THREE.Vector3();
  const transformed = new THREE.Vector3();
  const temp1 = new THREE.Vector3();
  const tempBoneMatrix = new THREE.Matrix4();
  const tempSkinnedVertex = new THREE.Vector3();
  const tempSkinned = new THREE.Vector3();

  const bindMatrix = mesh.bindMatrix;
  const bindMatrixInverse = mesh.bindMatrixInverse;

  for (let vndx = 0; vndx < mesh.geometry.vertices.length; ++vndx) {
    position.copy(mesh.geometry.vertices[vndx]);
    transformed.copy(position);

    for (let i = 0; i < mesh.geometry.morphTargets.length; ++i) {
      temp1.copy(mesh.geometry.morphTargets[i].vertices[vndx]);
      transformed.add(temp1.sub(position).multiplyScalar(mesh.morphTargetInfluences[i]));
    }

    tempSkinnedVertex.copy(transformed).applyMatrix4(bindMatrix);
    tempSkinned.set(0, 0, 0);

    const skinIndices = geometry.skinIndices[vndx];
    const skinWeights = geometry.skinWeights[vndx];

    for (let i = 0; i < 4; ++i) {
      const boneNdx = skinIndices.getComponent(i);
      const weight = skinWeights.getComponent(i);
      tempBoneMatrix.fromArray(skeleton.boneMatrices, boneNdx * 16);
      temp1.copy(tempSkinnedVertex);
      tempSkinned.add(temp1.applyMatrix4(tempBoneMatrix).multiplyScalar(weight));
    }

    transformed.copy(tempSkinned).applyMatrix4(bindMatrixInverse);
    transformed.applyMatrix4(mesh.matrixWorld);

Example:

 const scene = new THREE.Scene(); const camera = new THREE.PerspectiveCamera(75, 2, 0.1, 200); camera.position.z = 3; camera.position.y = 2; camera.lookAt(0, 0, 0); const renderer = new THREE.WebGLRenderer({canvas:document.querySelector('canvas')}); renderer.setSize(512, 256, false); document.body.appendChild(renderer.domElement); const geometry = new THREE.BoxGeometry(1, 1, 1); geometry.morphTargets.push({name: "morph", vertices: []}); for (const vertex of geometry.vertices) { geometry.skinIndices.push(new THREE.Vector4(vertex.x < 0 ? 0 : 1, 0, 0, 0)); geometry.skinWeights.push(new THREE.Vector4(1, 0, 0, 0)); geometry.morphTargets[0].vertices.push(vertex.clone().add(new THREE.Vector3(0, 1, 0))); } const material = new THREE.MeshPhongMaterial({ skinning: true, emissive: 0xffffff, wireframe: true, morphTargets: true }); const mesh = new THREE.SkinnedMesh(geometry, material); const bones = [new THREE.Bone(), new THREE.Bone()]; for (const bone of bones) { mesh.add(bone); } const skeleton = new THREE.Skeleton(bones); mesh.bind(skeleton); bones[0].position.x = -2; bones[1].position.x = 2; mesh.morphTargetInfluences[0] = 1; scene.add(mesh); const putMeshesAtSkinnedVertices = (function() { // These are so we can avoid doing allocations // in the inner loop. const position = new THREE.Vector3(); const transformed = new THREE.Vector3(); const temp1 = new THREE.Vector3(); const tempBoneMatrix = new THREE.Matrix4(); const tempSkinnedVertex = new THREE.Vector3(); const tempSkinned = new THREE.Vector3(); return function putMarkersAtSkinnedVertices(mesh, scene, marker, markerMaterial, markers) { const bindMatrix = mesh.bindMatrix; const bindMatrixInverse = mesh.bindMatrixInverse; const geometry = mesh.geometry; const vertices = geometry.vertices; const morphTargets = geometry.morphTargets; const skeleton = mesh.skeleton; for (let vndx = 0; vndx < vertices.length; ++vndx) { position.copy(vertices[vndx]); transformed.copy(position); for (let i = 0; i < morphTargets.length; ++i) { temp1.copy(morphTargets[i].vertices[vndx]); transformed.add(temp1.sub(position).multiplyScalar(mesh.morphTargetInfluences[i])); } tempSkinnedVertex.copy(transformed).applyMatrix4(bindMatrix); tempSkinned.set(0, 0, 0); const skinIndices = geometry.skinIndices[vndx]; const skinWeights = geometry.skinWeights[vndx]; for (let i = 0; i < 4; ++i) { const boneNdx = skinIndices.getComponent(i); const weight = skinWeights.getComponent(i); tempBoneMatrix.fromArray(skeleton.boneMatrices, boneNdx * 16); temp1.copy(tempSkinnedVertex); tempSkinned.add(temp1.applyMatrix4(tempBoneMatrix).multiplyScalar(weight)); } transformed.copy(tempSkinned).applyMatrix4(bindMatrixInverse); transformed.applyMatrix4(mesh.matrixWorld); // create them the first time this is called let markerMesh = markers[vndx]; if (!markerMesh) { markerMesh = new THREE.Mesh(marker, markerMaterial); markers[vndx] = markerMesh; scene.add(markerMesh); } markerMesh.position.copy(transformed); } } }()); // Make sure all matrices are up to date scene.updateMatrixWorld(); skeleton.update(); const marker = new THREE.BoxBufferGeometry(0.1, 0.1, 0.1); const markerMaterial = new THREE.MeshBasicMaterial({color: 0xFF0000}); const markers = []; putMeshesAtSkinnedVertices(mesh, scene, marker, markerMaterial, markers); (function render() { // requestAnimationFrame(render); renderer.render(scene, camera); })(); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/94/three.min.js"></script> <canvas></canvas> 

I did test it with this sample and it seemed to work.