awv3/three/ringgeometry.js

⚡ AWV3 embedded CAD

import * as THREE from 'three';

//note: number of vertices is constant in order to use the same vertex buffer
export default class RingGeometry extends THREE.BufferGeometry {
    constructor(segments) {
        super();

        this.parameters = {
            thetaSegments: segments,
            innerRadius: 1.0,
            outerRadius: 2.0,
            thetaStart: 0.0,
            thetaLength: 2*Math.PI,
        };

        let vertsCount = (segments + 1) * 2;
        let facesCount = segments * 2;
        this.setIndex(new THREE.BufferAttribute(new Uint32Array(facesCount * 3), 1));
        this.addAttribute('position', new THREE.BufferAttribute(new Float32Array(vertsCount * 3), 3));
        this.addAttribute('normal', new THREE.BufferAttribute(new Float32Array(vertsCount * 3), 3));
        this.attributes.position.dynamic = true;

        let f = 0;
        for (let i = 0; i < segments; i++)
            for (let idx of [2*i, 2*i+2, 2*i+3, 2*i+3, 2*i+1, 2*i])
                this.index.array[f++] = idx;
        let n = 0;
        for (let i = 0; i < vertsCount; i++)
            for (let crd of [0, 0, 1])
                this.attributes.normal.array[n++] = crd;

        this.updateParameters(this.parameters);
    }

    updateParameters(newParams) {
        Object.assign(this.parameters, newParams);
        let segments = this.parameters.thetaSegments;
        let vertexBuffer = this.attributes.position.array;
        for (let i = 0; i <= segments; i++) {
            let angle = this.parameters.thetaStart + this.parameters.thetaLength * i / segments;
            let cosA = Math.cos(angle), sinA = Math.sin(angle);
            let innerPos = new THREE.Vector3(cosA, sinA, 0).multiplyScalar(this.parameters.innerRadius);
            let outerPos = new THREE.Vector3(cosA, sinA, 0).multiplyScalar(this.parameters.outerRadius);
            vertexBuffer[6 * i + 0] = innerPos.x;
            vertexBuffer[6 * i + 1] = innerPos.y;
            vertexBuffer[6 * i + 2] = innerPos.z;
            vertexBuffer[6 * i + 3] = outerPos.x;
            vertexBuffer[6 * i + 4] = outerPos.y;
            vertexBuffer[6 * i + 5] = outerPos.z;
        }
        this.attributes.position.needsUpdate = true;
        //Note: this update may be done faster:
        this.computeBoundingSphere();
    }
};