从我尝试过(使用STLExporter.js),似乎只使用初始位置导出模型.
如果已经有办法做到这一点,或者是一个简单的解决方法,我会很感激在这方面的推动.
更新：在进一步深入了解内部结构之后,我已经想出(至少表面上看)为什么STLExporter不起作用. STLExporter查找所有对象并询问它们是否为Geometry对象的顶点和面.我的模型有一堆被剥皮的骨头.在动画步骤期间,骨骼会更新,但这些更新不会传播到原始Geometry对象.我知道这些变换顶点正在计算并存在于某处(它们会在画布上显示).
问题是这些变换的顶点和面存储在哪里,我可以访问它们以将它们导出为STL吗？
解决方法
The question is where are these transformed vertices and faces stored and can I access them to export them as an STL?
不幸的是,答案是无处可去的.这些都是在GPU上通过传入几个大型数组调用WebGL函数来计算的.
为了解释如何计算这个,我们首先回顾一下动画是如何工作的,使用this knight example作为参考.
SkinnedMesh对象包含一个骨架(由许多Bone组成)和一堆顶点.它们从所谓的bind pose开始排列.每个顶点绑定到0-4个骨骼,如果这些骨骼移动,顶点将移动,创建动画.
如果您采取我们的骑士示例,暂停动画中摆,并尝试standard STL exporter,生成的STL文件将完全是这个姿势,而不是动画.为什么？因为它只是查看mesh.geometry.vertices,它在动画期间不会从原始绑定姿势更改.只有骨骼会发生变化,GPU会进行一些数学运算来移动与每个骨骼相对应的顶点.
移动每个顶点的数学运算非常简单 – 在导出之前将绑定姿势顶点位置转换为骨骼空间,然后从骨骼空间转换为全局空间.
调整here的代码,我们将其添加到原始导出器：
vector.copy( vertices[ vertexIndex ] );
boneIndices = []; //which bones we need
boneIndices[0] = mesh.geometry.skinIndices[vertexIndex].x;
boneIndices[1] = mesh.geometry.skinIndices[vertexIndex].y;
boneIndices[2] = mesh.geometry.skinIndices[vertexIndex].z;
boneIndices[3] = mesh.geometry.skinIndices[vertexIndex].w;
weights = []; //some bones impact the vertex more than others
weights[0] = mesh.geometry.skinWeights[vertexIndex].x;
weights[1] = mesh.geometry.skinWeights[vertexIndex].y;
weights[2] = mesh.geometry.skinWeights[vertexIndex].z;
weights[3] = mesh.geometry.skinWeights[vertexIndex].w;
inverses = []; //boneInverses are the transform from bind-pose to some "bone space"
inverses[0] = mesh.skeleton.boneInverses[ boneIndices[0] ];
inverses[1] = mesh.skeleton.boneInverses[ boneIndices[1] ];
inverses[2] = mesh.skeleton.boneInverses[ boneIndices[2] ];
inverses[3] = mesh.skeleton.boneInverses[ boneIndices[3] ];
skinMatrices = []; //each bone's matrix world is the transform from "bone space" to the "global space"
skinMatrices[0] = mesh.skeleton.bones[ boneIndices[0] ].matrixWorld;
skinMatrices[1] = mesh.skeleton.bones[ boneIndices[1] ].matrixWorld;
skinMatrices[2] = mesh.skeleton.bones[ boneIndices[2] ].matrixWorld;
skinMatrices[3] = mesh.skeleton.bones[ boneIndices[3] ].matrixWorld;
var finalVector = new THREE.Vector4();
for(var k = 0; k<4; k++) {
var tempVector = new THREE.Vector4(vector.x,vector.y,vector.z);
//weight the transformation
tempVector.multiplyScalar(weights[k]);
//the inverse takes the vector into local bone space
tempVector.applyMatrix4(inverses[k])
//which is then transformed to the appropriate world space
.applyMatrix4(skinMatrices[k]);
finalVector.add(tempVector);
}
output += '\t\t\tvertex ' + finalVector.x + ' ' + finalVector.y + ' ' + finalVector.z + '\n';
这会产生如下所示的STL文件：
完整代码可在https://gist.github.com/kjlubick/fb6ba9c51df63ba0951f获得
