CADViewComponent/src/Orbit.ts

import * as THREE from "three";

/**
 * 轨道控制的数学类,观察向量和角度的互相转换
 * 当x当抬头或者低头到90度时,触发万向锁.
 * 
 * @class Orbit
 */
export class Orbit
{
    //抬头低头 正数抬头 负数低头
    private m_RoX: number = 0;

    //身体旋转 0为正右边 逆时针旋转
    RoZ: number = 0;

    get RoX()
    {
        return this.m_RoX;
    }
    set RoX(v)
    {
        this.m_RoX = THREE.Math.clamp(v, Math.PI * -0.5, Math.PI * 0.5);
    }

    /**
     * 使用旋转角度 计算观察向量
     * 
     * @param {THREE.Vector3} [dir] 引用传入,如果传入,那么就不构造新的向量
     * @returns {THREE.Vector3} 返回观察向量
     * @memberof Orbit
     */
    UpdateDirection(dir?: THREE.Vector3): THREE.Vector3
    {
        let rtDir = dir ? dir : new THREE.Vector3();

        rtDir.z = Math.sin(this.m_RoX);

        //归一化专用.
        let d = Math.abs(Math.cos(this.m_RoX));

        rtDir.x = Math.cos(this.RoZ) * d;
        rtDir.y = Math.sin(this.RoZ) * d;

        return rtDir;
    }

    /**
     * 使用观察向量,计算旋转角度
     * 
     * @param {THREE.Vector3} dir 
     * @memberof Orbit
     */
    UpdateRoValue(dir: THREE.Vector3)
    {
        dir.normalize();
        this.m_RoX = Math.asin(dir.z);
        if (dir.x < 1e-4 && dir.y < 1e-4)
            this.RoZ = Math.PI * 0.5;
        else
            this.RoZ = Math.atan2(dir.y, dir.x);
    }

    /**
     * 
     * 根据观察向量 求头部的向量.
     * 
     * @static
     * @param {THREE.Vector3} dir 
     * @param {THREE.Vector3} [up] 
     * @returns {THREE.Vector3} 
     * @memberof Orbit
     */
    static ComputUpDirection(dir: THREE.Vector3, up?: THREE.Vector3): THREE.Vector3
    {
        let upRes = up ? up : new THREE.Vector3();
        if (dir.equals(new THREE.Vector3(0, 0, -1)))
        {
            upRes.set(0, 1, 0);
        }
        else if (dir.equals(new THREE.Vector3(0, 0, 1)))
        {
            upRes.set(0, -1, 0);
        }
        else
        {
            let xv = new THREE.Vector3();
            xv.crossVectors(new THREE.Vector3(0, 0, 1), dir);
            upRes.crossVectors(dir, xv);
            upRes.normalize();
        }
        return upRes;
    }
}