3D Boolean operations with Three CSG - three.js

Question

Following the example here:
http://learningthreejs.com/blog/2011/12/10/constructive-solid-geometry-with-csg-js/
And using Three.js with https://github.com/chandlerprall/ThreeCSG, I'm trying to do 3D boolean operations on nodes from the model. Like for example if I have a wall with a window, I want to do invert() on that to get just the window.
I have a function that returns all the vertices of the polygons of a node, here's an example of vertices of an object without holes https://pastebin.com/8dhYzPwE.
I'm using ThreeCSG like this:
const geometryThree = new THREE.Geometry();
geometryThree.vertices.push(
...vertices
);
const geometryCsg = new ThreeBSP(geometryThree);
But that's what I'm getting in geometryCsg:
"{
"matrix": {
"elements": {
"0": 1,
"1": 0,
"2": 0,
"3": 0,
"4": 0,
"5": 1,
"6": 0,
"7": 0,
"8": 0,
"9": 0,
"10": 1,
"11": 0,
"12": 0,
"13": 0,
"14": 0,
"15": 1
}
},
"tree": {
"polygons": []
}
}"
I think it's because the geometry.faces.length is 0.
How can I make the vertices array to be a proper Three.Geometry such that the faces won't be empty? Geometry.elementsNeedsUpdate doesn't work...
Is there an example that uses polygons of a shape as an array of Vector3s and transforms that to csg?

Answer 1

I just worked on a demo using THREE csg: the Viewer meshes have an indexed array of vertices so you cannot create a BSP directly out of it. Also my code is using a web worker to process the meshes in order to keep the UI responsive with large models, so I need first to send the mesh data to the worker and reconstruct a simple THREE.Mesh on the worker side, the code looks like below:
// Sends component geometry to the web worker
postComponent (dbId) {
const geometry = this.getComponentGeometry(dbId)
const msg = {
boundingBox: this.getComponentBoundingBox(dbId),
matrixWorld: geometry.matrixWorld,
nbMeshes: geometry.meshes.length,
msgId: 'MSG_ID_COMPONENT',
dbId
}
geometry.meshes.forEach((mesh, idx) => {
msg['positions' + idx] = mesh.positions
msg['indices' + idx] = mesh.indices
msg['stride' + idx] = mesh.stride
})
this.worker.postMessage(msg)
}
// get geometry for all fragments in a component
getComponentGeometry (dbId) {
const fragIds = Toolkit.getLeafFragIds(
this.viewer.model, dbId)
let matrixWorld = null
const meshes = fragIds.map((fragId) => {
const renderProxy = this.viewer.impl.getRenderProxy(
this.viewer.model,
fragId)
const geometry = renderProxy.geometry
const attributes = geometry.attributes
const positions = geometry.vb
? geometry.vb
: attributes.position.array
const indices = attributes.index.array || geometry.ib
const stride = geometry.vb ? geometry.vbstride : 3
const offsets = geometry.offsets
matrixWorld = matrixWorld ||
renderProxy.matrixWorld.elements
return {
positions,
indices,
offsets,
stride
}
})
return {
matrixWorld,
meshes
}
}
// On the worker side reconstruct THREE.Mesh
// from received data and create ThreeBSP
function buildComponentMesh (data) {
const vertexArray = []
for (let idx=0; idx < data.nbMeshes; ++idx) {
const meshData = {
positions: data['positions' + idx],
indices: data['indices' + idx],
stride: data['stride' + idx]
}
getMeshGeometry (meshData, vertexArray)
}
const geometry = new THREE.Geometry()
for (var i = 0; i < vertexArray.length; i += 3) {
geometry.vertices.push(vertexArray[i])
geometry.vertices.push(vertexArray[i + 1])
geometry.vertices.push(vertexArray[i + 2])
const face = new THREE.Face3(i, i + 1, i + 2)
geometry.faces.push(face)
}
const matrixWorld = new THREE.Matrix4()
matrixWorld.fromArray(data.matrixWorld)
const mesh = new THREE.Mesh(geometry)
mesh.applyMatrix(matrixWorld)
mesh.boundingBox = data.boundingBox
mesh.bsp = new ThreeBSP(mesh)
mesh.dbId = data.dbId
return mesh
}
function getMeshGeometry (data, vertexArray) {
const offsets = [{
count: data.indices.length,
index: 0,
start: 0}
]
for (var oi = 0, ol = offsets.length; oi < ol; ++oi) {
var start = offsets[oi].start
var count = offsets[oi].count
var index = offsets[oi].index
for (var i = start, il = start + count; i < il; i += 3) {
const a = index + data.indices[i]
const b = index + data.indices[i + 1]
const c = index + data.indices[i + 2]
const vA = new THREE.Vector3()
const vB = new THREE.Vector3()
const vC = new THREE.Vector3()
vA.fromArray(data.positions, a * data.stride)
vB.fromArray(data.positions, b * data.stride)
vC.fromArray(data.positions, c * data.stride)
vertexArray.push(vA)
vertexArray.push(vB)
vertexArray.push(vC)
}
}
}
The complete code of my sample is there: Wall Analyzer and the live demo there.