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March 4, 2022 19:57
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| // Creates UVs for THREE js geometry | |
| // useful for if you need to add a texture to a concave hull, for example | |
| import * as THREE from 'three'; | |
| function generateUvs(geometry) { | |
| const uvNumComponents = 2; | |
| geometry.computeVertexNormals(); | |
| function pointsInPlaneToPoints2D(points3D) { | |
| // The normal is a unit vector that sticks out from face. | |
| // We're using the first 3 points, assuming that there | |
| // are at least 3, and they are not co-linear. | |
| const [p0, p1, p2] = points3D; | |
| const planeNormal = new THREE.Vector3() | |
| .crossVectors( | |
| new THREE.Vector3().subVectors(p0, p1), | |
| new THREE.Vector3().subVectors(p1, p2) | |
| ) | |
| .normalize(); | |
| // Unit vector on the Z axis, where we want to rotate our face | |
| const zUnit = new THREE.Vector3(0, 0, 1); | |
| // Quaternion representing the rotation of the face plane to Z | |
| const qRot = new THREE.Quaternion().setFromUnitVectors(planeNormal, zUnit); | |
| // Rotate each point, assuming that they are all co-planar | |
| // with the first 3. | |
| return points3D.map(function (p) { | |
| const pRot = p.clone().applyQuaternion(qRot); | |
| // Output format [x, y] (ignoring z) | |
| return [pRot.x, pRot.y]; | |
| }); | |
| } | |
| var verts = geometry.attributes.position.array.length / 3; | |
| var b = []; | |
| var g = []; | |
| var uvs = []; | |
| let pos = geometry.attributes.position; | |
| let norm = geometry.attributes.normal; | |
| var newNormal = []; | |
| Array.from({ length: verts }).forEach((s, i) => { | |
| let vertex = new THREE.Vector3(pos.getX(i), pos.getY(i), pos.getZ(i)); | |
| let normal = new THREE.Vector3(norm.getX(i), norm.getY(i), norm.getZ(i)); | |
| b.push(vertex); | |
| g.push(normal); | |
| if (b.length == 3) { | |
| var flatten = pointsInPlaneToPoints2D(b); | |
| newNormal.push(...flatten.flat()); | |
| b = []; | |
| } | |
| }); | |
| geometry.setAttribute( | |
| 'uv', | |
| new THREE.BufferAttribute(new Float32Array(newNormal), uvNumComponents) | |
| ); | |
| return geometry; | |
| } |
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