三.js计算STL文件网格体积 [英] three.js calculate STL file mesh volume

问题描述

我必须计算一个 STL 文件的体积，我成功地得到了模型的大小

I have to calculate the volume of an STL file, I successfully got the sizes of the model with

var box = new THREE.Box3().setFromObject( mesh );
var sizes = box.getSize();

但我就是无法理解计算它的概念.我用

but I just can't wrap my head around the concept of calculating it. I load the model with

var loader = new THREE.STLLoader();
loader.load(stlFileURL, function ( geometry ) {});

有人可以帮我指出正确的方向吗?我是用 javascript 做的.

Can someone help me out and point me in the right direction? I'm doing it with javascript.

推荐答案

你可以从我的评论中找到算法.

You can find it with the algorithm from my comment.

在代码片段中，体积是在没有缩放的情况下计算的.

In the code snippet, the volume is computed without scaling.

此外，我添加了一个简单的检查，该算法通过查找空心圆柱体的体积来正确计算.由于 THREE.STLLoader() 返回非索引几何，我也将圆柱体的几何转换为非索引.

Also, I've added a simple check that the algorithm calculates correctly by finding the volume of a hollow cylinder. As THREE.STLLoader() returns a non-indexed geometry, I've casted the geometry of the cylinder to non-indexed too.

相关论坛主题

var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 0.01, 1000);
camera.position.setScalar(20);
var renderer = new THREE.WebGLRenderer();
renderer.setClearColor(0x404040);
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

var controls = new THREE.OrbitControls(camera, renderer.domElement);

var loader = new THREE.STLLoader();
loader.load('https://threejs.org/examples/models/stl/binary/pr2_head_pan.stl', function(geometry) {

  var mesh = new THREE.Mesh(geometry, new THREE.MeshBasicMaterial({
    color: 0xff00ff,
    wireframe: true
  }));
  mesh.rotation.set(-Math.PI / 2, 0, 0);
  mesh.scale.setScalar(100);
  scene.add(mesh);

  console.log("stl volume is " + getVolume(geometry));
});

// check with known volume:
var hollowCylinderGeom = new THREE.LatheBufferGeometry([
  new THREE.Vector2(1, 0),
  new THREE.Vector2(2, 0),
  new THREE.Vector2(2, 2),
  new THREE.Vector2(1, 2),
  new THREE.Vector2(1, 0)
], 90).toNonIndexed();
console.log("pre-computed volume of a hollow cylinder (PI * (R^2 - r^2) * h): " + Math.PI * (Math.pow(2, 2) - Math.pow(1, 2)) * 2);
console.log("computed volume of a hollow cylinder: " + getVolume(hollowCylinderGeom));


function getVolume(geometry) {

  let position = geometry.attributes.position;
  let faces = position.count / 3;
  let sum = 0;
  let p1 = new THREE.Vector3(),
    p2 = new THREE.Vector3(),
    p3 = new THREE.Vector3();
  for (let i = 0; i < faces; i++) {
    p1.fromBufferAttribute(position, i * 3 + 0);
    p2.fromBufferAttribute(position, i * 3 + 1);
    p3.fromBufferAttribute(position, i * 3 + 2);
    sum += signedVolumeOfTriangle(p1, p2, p3);
  }
  return sum;

}

function signedVolumeOfTriangle(p1, p2, p3) {
  return p1.dot(p2.cross(p3)) / 6.0;
}

renderer.setAnimationLoop(() => {
  renderer.render(scene, camera);
});

body {
  overflow: hidden;
  margin: 0;
}

<script src="https://threejs.org/build/three.min.js"></script>
<script src="https://threejs.org/examples/js/loaders/STLLoader.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>

这篇关于三.js计算STL文件网格体积的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！