使用Three.js翻转（镜像）任何对象

Question

更新2019

由于r89 three.js也会调整面部和法线。要翻转/镜像对象，只需使用：

object3D.applyMatrix(new THREE.Matrix4().makeScale(-1, 1, 1));

不需要原始解决方案中显示的其他调整。链接到票证：Support reflection matrices. #12787

原始问题

我正在尝试创建一个可以翻转Three.js场景中任何对象的实用程序。翻转本身很容易：

object3D.applyMatrix(new THREE.Matrix4().makeScale(-1, 1, 1));

证明困难的是在翻转后修复面部和法线。结果看起来很混乱。源和翻转对象的图像：https://dl.dropboxusercontent.com/u/20925853/Flipped.png

我已经看过许多线程讨论了这个和类似的问题，但没有找到任何可用的东西。有人知道我在那里失踪了吗？ - 谢谢！

Js小提琴上的示例代码： https://jsfiddle.net/7dwh084w/

var renderer;
var scene;
var camera;

function render() {

    renderer.render(scene, camera);
};

function load(callback) {

    new THREE.ColladaLoader().load("https://dl.dropboxusercontent.com/u/20925853/Kitchen.dae", function (result) {

        var mesh = result.scene.children[0].children[0].clone();
        if (callback) callback(mesh);
    });
}

function init() {

    scene = new THREE.Scene();
    camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 10000);
    camera.position.z = 1000;

    var light = new THREE.DirectionalLight(0xffffff);
    light.position.set(2, 1, 1).normalize();
    scene.add(light);
    var ambient = new THREE.AmbientLight(0x777777);
    scene.add(ambient);

    var controls = new THREE.OrbitControls(camera);
    controls.damping = 0.2;
    controls.addEventListener('change', render);

    renderer = new THREE.WebGLRenderer();
    renderer.setSize(window.innerWidth, window.innerHeight);
    document.body.appendChild(renderer.domElement);

    load(function (mesh) {

        flipMesh(mesh);

        scene.add(mesh);
        render();
    });

    render();
}

function flipMesh(object3D) {

    object3D.applyMatrix(new THREE.Matrix4().makeScale(-1, 1, 1));
    reverseWindingOrder(object3D);
}

function reverseWindingOrder(object3D) {

    // TODO: Something is missing, the objects are flipped alright but the light reflection on them is somehow broken

    if (object3D.type === "Mesh") {

        var geometry = object3D.geometry;

        for (var i = 0, l = geometry.faces.length; i < l; i++) {

            var face = geometry.faces[i];
            var temp = face.a;
            face.a = face.c;
            face.c = temp;

        }

        var faceVertexUvs = geometry.faceVertexUvs[0];
        for (i = 0, l = faceVertexUvs.length; i < l; i++) {

            var vector2 = faceVertexUvs[i][0];
            faceVertexUvs[i][0] = faceVertexUvs[i][2];
            faceVertexUvs[i][2] = vector2;
        }

        geometry.computeFaceNormals();
        geometry.computeVertexNormals();
    }

    if (object3D.children) {

        for (var j = 0, jl = object3D.children.length; j < jl; j++) {

            reverseWindingOrder(object3D.children[j]);
        }
    }
}

init();

Answer 1

我在项目中使用以下代码来翻转对象：

    const scale = new THREE.Vector3(1, 1, 1);
    if (flipX) {
        scale.x *= -1;
    }
    if (flipY) {
        scale.z *= -1;
    }
    object.scale.multiply(scale);

希望这会有所帮助。