FacesGeometry.js

import * as THREE from 'three'

export class FacesGeometry extends THREE.BufferGeometry {
    constructor(
        inputVertices = [new THREE.Vector3(0, 0, 0), new THREE.Vector3(1, 0, 0), new THREE.Vector3(0, 1, 0), new THREE.Vector3(0, 0, 1)],
        inputIndices = [
            0, 1, 2,
            0, 2, 3,
            0, 3, 1,
            3, 2, 1]
        ) {
        super();
        this.type = 'FacesGeometry';
        this.parameters = {
            inputVertices: inputVertices,
            inputIndices: inputIndices
        };

        const vertices = [];
        const normals = [];
        const uvs = [];
        const indices = [];
        for (let i = 0; i<inputIndices.length/3; i++) {
            vertices.push(inputVertices[inputIndices[i*3+0]].x, inputVertices[inputIndices[i*3+0]].y, inputVertices[inputIndices[i*3+0]].z);
            vertices.push(inputVertices[inputIndices[i*3+1]].x, inputVertices[inputIndices[i*3+1]].y, inputVertices[inputIndices[i*3+1]].z);
            vertices.push(inputVertices[inputIndices[i*3+2]].x, inputVertices[inputIndices[i*3+2]].y, inputVertices[inputIndices[i*3+2]].z);
            const normal = new THREE.Vector3().crossVectors(inputVertices[inputIndices[i*3+0]].clone().sub(inputVertices[inputIndices[i*3+1]]), inputVertices[inputIndices[i*3+0]].clone().sub(inputVertices[inputIndices[i*3+2]])).normalize();
            normals.push(normal.x, normal.y, normal.z);
            normals.push(normal.x, normal.y, normal.z);
            normals.push(normal.x, normal.y, normal.z);
            uvs.push(0, 0, 0, 0, 0, 0);
            indices.push(i*3+0, i*3+1, i*3+2);
        }
        this.setIndex(indices);
        this.setAttribute( 'position', new THREE.Float32BufferAttribute( vertices, 3 ) );
        this.setAttribute( 'normal', new THREE.Float32BufferAttribute( normals, 3 ) );
        this.setAttribute( 'uv', new THREE.Float32BufferAttribute( uvs, 2 ) );
    }

    copy( source ) {
        super.copy( source );
        this.parameters = Object.assign( {}, source.parameters );
        return this;
    }

}