Question

我正在学习Three.js，并且正在研究太阳系的模型以了解其工作原理。所以我有一个场景，地球围绕太阳旋转，月亮围绕地球旋转。

现在，我想专注于月球并使用控件围绕月球旋转（同时将其始终保持在屏幕中央）。 OrbitControls似乎是最理想的选择，但我无法让它们与移动的Moon配合使用。

这是我的3次尝试（请忽略地球和月球是立方体）。

尝试1-放置相机（jsfiddle）

首先，我创建了一个场景，其中camera是月球的孩子（没有OrbitControls）。

moon.add(camera);
camera.lookAt(0, 0, 0);

var camera, controls, scene, renderer, labelRenderer;
var solarPlane, earth, moon;
var angle = 0;

function buildScene() {
  scene = new THREE.Scene();
  solarPlane = createSolarPlane();
  earth = createBody("Earth");
  moon = createBody("Moon");

  scene.add(solarPlane);
  solarPlane.add(earth);
  earth.add(moon);

  moon.add(camera);
}

init();
animate();

function init() {

  renderer = new THREE.WebGLRenderer({
    antialias: false
  });
  renderer.setPixelRatio(window.devicePixelRatio);
  renderer.setSize(window.innerWidth, window.innerHeight);
  document.body.appendChild(renderer.domElement);

  labelRenderer = new THREE.CSS2DRenderer();
  labelRenderer.setSize(window.innerWidth, window.innerHeight);
  labelRenderer.domElement.style.position = 'absolute';
  labelRenderer.domElement.style.top = '0';
  labelRenderer.domElement.style.pointerEvents = 'none';
  document.body.appendChild(labelRenderer.domElement);

  camera = new THREE.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 0.1, 1000);
  camera.position.set(13.670839104116506, 10.62941701834559, 0.3516419193657562);
  camera.lookAt(0, 0, 0);

  buildScene();
}

function animate(time) {

  angle = (angle + .005) % (2 * Math.PI);
  rotateBody(earth, angle, 1);
  rotateBody(moon, angle, 2);

  render();
  requestAnimationFrame(animate);

  function rotateBody(body, angle, radius) {
    body.rotation.x = angle;
    body.position.x = radius * Math.cos(angle);
    body.position.y = radius * Math.sin(angle);
    body.position.z = radius * Math.sin(angle);
  }
}

function render() {
  renderer.render(scene, camera);
  labelRenderer.render(scene, camera);
}

function createBody(name, parent) {
  var geometry = new THREE.CubeGeometry(1, 1, 1);
  const body = new THREE.Mesh(geometry, new THREE.MeshNormalMaterial());
  body.position.set(1, 1, 1);
  body.scale.set(.3, .3, .3);
  body.name = name;
  body.add(makeTextLabel(name));
  return body;
}

function createSolarPlane() {
  var solarPlane = new THREE.GridHelper(5, 10);
  solarPlane.add(makeTextLabel("solar plane"));
  return solarPlane;
}

function makeTextLabel(label) {
  var text = document.createElement('div');
  text.style.color = 'rgb(255, 255, 255)';
  text.textContent = label;
  return new THREE.CSS2DObject(text);
}

body {
  margin: 0;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/98/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>
<script src="https://threejs.org/examples/js/renderers/CSS2DRenderer.js"></script>

结果：它很好地将月球放在了中心，但是显然您无法导航场景，因为我还没有聘用OrbitControls。但这只是参考。

尝试2-添加OrbitControls（jsfiddle）

然后我添加了OrbitControls。

var camera, controls, scene, renderer, labelRenderer;
var solarPlane, earth, moon;
var angle = 0;

function buildScene() {
  scene = new THREE.Scene();
  solarPlane = createSolarPlane();
  earth = createBody("Earth");
  moon = createBody("Moon");

  scene.add(solarPlane);
  solarPlane.add(earth);
  earth.add(moon);

  moon.add(camera);
}

init();
animate();

function init() {

  renderer = new THREE.WebGLRenderer({
    antialias: false
  });
  renderer.setPixelRatio(window.devicePixelRatio);
  renderer.setSize(window.innerWidth, window.innerHeight);
  document.body.appendChild(renderer.domElement);

  labelRenderer = new THREE.CSS2DRenderer();
  labelRenderer.setSize(window.innerWidth, window.innerHeight);
  labelRenderer.domElement.style.position = 'absolute';
  labelRenderer.domElement.style.top = '0';
  labelRenderer.domElement.style.pointerEvents = 'none';
  document.body.appendChild(labelRenderer.domElement);

  camera = new THREE.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 0.1, 1000);
  camera.position.set(13.670839104116506, 10.62941701834559, 0.3516419193657562);
  camera.lookAt(0, 0, 0);

  buildScene();

  controls = new THREE.OrbitControls(camera, renderer.domElement);
  controls.enablePan = false;
  controls.enableDamping = false;
}

function animate(time) {

  angle = (angle + .005) % (2 * Math.PI);
  rotateBody(earth, angle, 1);
  rotateBody(moon, angle, 2);

  render();
  requestAnimationFrame(animate);

  function rotateBody(body, angle, radius) {
    body.rotation.x = angle;
    body.position.x = radius * Math.cos(angle);
    body.position.y = radius * Math.sin(angle);
    body.position.z = radius * Math.sin(angle);
  }
}

function render() {
  renderer.render(scene, camera);
  labelRenderer.render(scene, camera);
}

function createBody(name, parent) {
  var geometry = new THREE.CubeGeometry(1, 1, 1);
  const body = new THREE.Mesh(geometry, new THREE.MeshNormalMaterial());
  body.position.set(1, 1, 1);
  body.scale.set(.3, .3, .3);
  body.name = name;
  body.add(makeTextLabel(name));
  return body;
}

function createSolarPlane() {
  var solarPlane = new THREE.GridHelper(5, 10);
  solarPlane.add(makeTextLabel("solar plane"));
  return solarPlane;
}

function makeTextLabel(label) {
  var text = document.createElement('div');
  text.style.color = 'rgb(255, 255, 255)';
  text.textContent = label;
  return new THREE.CSS2DObject(text);
}

body {
  margin: 0;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/98/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>
<script src="https://threejs.org/examples/js/renderers/CSS2DRenderer.js"></script>

结果：月球已从中心移到侧面（不知道为什么吗？）。当您开始使用鼠标导航时，一切都会变得疯狂。效果就像OrbitControls围绕场景中心导航，而相机围绕其父对象（月亮）导航。实际上，它们不会以一致的方式更改状态，并且一切都变得疯狂。

尝试3-控制轨道的目标（jsfiddle）

我尝试的最后一个选择是强行设置controls.target，使其始终指向月球。因为月亮不断地移动，所以我必须在每次渲染之前完成。

const p = new THREE.Vector3();
const q = new THREE.Quaternion();
const s = new THREE.Vector3();
moon.matrixWorld.decompose(p, q, s);

// now setting controls target to Moon's position (in scene's coordinates)
controls.target.copy(p); 

render();

var camera, controls, scene, renderer, labelRenderer;
var solarPlane, earth, moon;
var angle = 0;
const p = new THREE.Vector3();
const q = new THREE.Quaternion();
const s = new THREE.Vector3();

function buildScene() {
  scene = new THREE.Scene();
  solarPlane = createSolarPlane();
  earth = createBody("Earth");
  moon = createBody("Moon");

  scene.add(solarPlane);
  solarPlane.add(earth);
  earth.add(moon);

  moon.add(camera);
}

init();
animate();

function init() {

  renderer = new THREE.WebGLRenderer({
    antialias: false
  });
  renderer.setPixelRatio(window.devicePixelRatio);
  renderer.setSize(window.innerWidth, window.innerHeight);
  document.body.appendChild(renderer.domElement);

  labelRenderer = new THREE.CSS2DRenderer();
  labelRenderer.setSize(window.innerWidth, window.innerHeight);
  labelRenderer.domElement.style.position = 'absolute';
  labelRenderer.domElement.style.top = '0';
  labelRenderer.domElement.style.pointerEvents = 'none';
  document.body.appendChild(labelRenderer.domElement);

  camera = new THREE.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 0.1, 1000);
  camera.position.set(13.670839104116506, 10.62941701834559, 0.3516419193657562);
  camera.lookAt(0, 0, 0);

  buildScene();

  controls = new THREE.OrbitControls(camera, renderer.domElement);
  controls.enablePan = false;
  controls.enableDamping = false;
}

function animate(time) {

  angle = (angle + .005) % (2 * Math.PI);
  rotateBody(earth, angle, 1);
  rotateBody(moon, angle, 2);

  moon.matrixWorld.decompose(p, q, s);
  controls.target.copy(p);

  render();
  requestAnimationFrame(animate);

  function rotateBody(body, angle, radius) {
    body.rotation.x = angle;
    body.position.x = radius * Math.cos(angle);
    body.position.y = radius * Math.sin(angle);
    body.position.z = radius * Math.sin(angle);
  }
}

function render() {
  renderer.render(scene, camera);
  labelRenderer.render(scene, camera);
}

function createBody(name, parent) {
  var geometry = new THREE.CubeGeometry(1, 1, 1);
  const body = new THREE.Mesh(geometry, new THREE.MeshNormalMaterial());
  body.position.set(1, 1, 1);
  body.scale.set(.3, .3, .3);
  body.name = name;
  body.add(makeTextLabel(name));
  return body;
}

function createSolarPlane() {
  var solarPlane = new THREE.GridHelper(5, 10);
  solarPlane.add(makeTextLabel("solar plane"));
  return solarPlane;
}

function makeTextLabel(label) {
  var text = document.createElement('div');
  text.style.color = 'rgb(255, 255, 255)';
  text.textContent = label;
  return new THREE.CSS2DObject(text);
}

body {
  margin: 0;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/98/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>
<script src="https://threejs.org/examples/js/renderers/CSS2DRenderer.js"></script>

结果：最初，月亮位于屏幕的侧面（与第二次尝试的位置相同），但是随后当您开始导航时，月亮“跳”到屏幕的中心屏幕上，您可以浏览它。几乎完美。只要您不缩放即可。放大/缩小时，您开始看到月亮在缩放过程中旋转。

问题

为什么OrbitControls不尊重相机的父母是月球的事实，并且一直在场景中心附近导航？
为什么在添加OrbitControls之后，月亮会“跳到”屏幕的侧面？
使它工作的优雅方式是什么？（由于缩放问题，迫使target循环跟随月球既不优雅也不起作用）？

r。 98

编辑：编辑性修改使句子更清晰。

Answer 1

我通过引入伪造的相机使其工作，除了camera.parent

之外，它与原始相机具有相同的功能

fakeCamera = camera.clone(); // parent becomes null
controls = new THREE.OrbitControls(fakeCamera, renderer.domElement);

通过这种方式OrbitControls的摄像机具有自己的坐标系。

然后，在渲染之前，我将fakeCamera的值复制回用于渲染的真实相机。

camera.position.copy(fakeCamera.position);
camera.quaternion.copy(fakeCamera.quaternion);
camera.scale.copy(fakeCamera.scale);

render();

效果很好。

编辑

我注意到

camera.position.copy(fakeCamera.position);
camera.quaternion.copy(fakeCamera.quaternion);
camera.scale.copy(fakeCamera.scale);

可以替换为

camera.copy(fakeCamera);

（下面的代码已相应更新）

var camera, fakeCamera, controls, scene, renderer, labelRenderer;
var solarPlane, earth, moon;
var angle = 0;

function buildScene() {
  scene = new THREE.Scene();
  solarPlane = createSolarPlane();
  earth = createBody("Earth");
  moon = createBody("Moon");

  scene.add(solarPlane);
  solarPlane.add(earth);
  earth.add(moon);

  moon.add(camera);
}

init();
animate();

function init() {

  renderer = new THREE.WebGLRenderer({
    antialias: false
  });
  renderer.setPixelRatio(window.devicePixelRatio);
  renderer.setSize(window.innerWidth, window.innerHeight);
  document.body.appendChild(renderer.domElement);

  labelRenderer = new THREE.CSS2DRenderer();
  labelRenderer.setSize(window.innerWidth, window.innerHeight);
  labelRenderer.domElement.style.position = 'absolute';
  labelRenderer.domElement.style.top = '0';
  labelRenderer.domElement.style.pointerEvents = 'none';
  document.body.appendChild(labelRenderer.domElement);

  camera = new THREE.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 0.1, 1000);
  camera.position.set(13.670839104116506, 10.62941701834559, 0.3516419193657562);
  camera.lookAt(0, 0, 0);

  buildScene();

  fakeCamera = camera.clone();
  controls = new THREE.OrbitControls(fakeCamera, renderer.domElement);
  controls.enablePan = false;
  controls.enableDamping = false;
}

function animate(time) {

  angle = (angle + .005) % (2 * Math.PI);
  rotateBody(earth, angle, 1);
  rotateBody(moon, angle, 2);

  camera.copy(fakeCamera);

  render();
  requestAnimationFrame(animate);

  function rotateBody(body, angle, radius) {
    body.rotation.x = angle;
    body.position.x = radius * Math.cos(angle);
    body.position.y = radius * Math.sin(angle);
    body.position.z = radius * Math.sin(angle);
  }
}

function render() {
  renderer.render(scene, camera);
  labelRenderer.render(scene, camera);
}

function createBody(name, parent) {
  var geometry = new THREE.CubeGeometry(1, 1, 1);
  const body = new THREE.Mesh(geometry, new THREE.MeshNormalMaterial());
  body.position.set(1, 1, 1);
  body.scale.set(.3, .3, .3);
  body.name = name;
  body.add(makeTextLabel(name));
  return body;
}

function createSolarPlane() {
  var solarPlane = new THREE.GridHelper(5, 10);
  solarPlane.add(makeTextLabel("solar plane"));
  return solarPlane;
}

function makeTextLabel(label) {
  var text = document.createElement('div');
  text.style.color = 'rgb(255, 255, 255)';
  text.textContent = label;
  return new THREE.CSS2DObject(text);
}

body {
  margin: 0;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/98/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>
<script src="https://threejs.org/examples/js/renderers/CSS2DRenderer.js"></script>

Answer 2

我认为您的解决方法是一个不错的解决方案，因为它不需要修改导入的代码。另外，只要不用于渲染，额外的相机维护成本就不高。基于相同的原理，这是一个可以应用的OrbitControls子类。请注意，localTarget属性只是target属性的别名。没有globalTarget属性。

THREE.OrbitControlsLocal = function ( realObject, domElement ) {
    this.realObject = realObject;
    //Camera and Object3D have different forward direction:
    let placeholderObject = realObject.isCamera ? new THREE.PerspectiveCamera() : new THREE.Object3D;
    this.placeholderObject = placeholderObject;

    THREE.OrbitControls.call( this, placeholderObject, domElement );

    let globalUpdate = this.update;
    this.globalUpdate = globalUpdate;
    this.update = function() {

        //This responds to changes made to realObject from outside the controls:
        placeholderObject.position.copy( realObject.position );
        placeholderObject.quaternion.copy( realObject.quaternion);
        placeholderObject.scale.copy( realObject.scale );
        placeholderObject.up.copy( realObject.up );

        var retval = globalUpdate();
        realObject.position.copy( placeholderObject.position );
        realObject.quaternion.copy( placeholderObject.quaternion);
        realObject.scale.copy( placeholderObject.scale );
        return retval ;

    };

    this.update();
};

THREE.OrbitControlsLocal.prototype = Object.create(THREE.OrbitControls.prototype);
THREE.OrbitControlsLocal.prototype.constructor = THREE.OrbitControlsLocal;

Object.defineProperties(THREE.OrbitControlsLocal.prototype, {
    localTarget: {
        get: ()=>this.target,
        set: v=>this.target=v
    }
});

我以前的解决方案，在应用lookAt之前仅将本地目标转换为世界空间是不正确的。问题似乎在于，每次更新时lookAt都会根据其世界空间向上方向（camera.up或object.up）对照相机进行定向。占位符/ fakeCamera解决方案不存在此问题。（请参见PR https://github.com/mrdoob/three.js/pull/16374）

迫使OrbitControls在移动的物体上导航（几乎可以正常工作）

尝试1-放置相机（jsfiddle）

尝试2-添加OrbitControls（jsfiddle）

尝试3-控制轨道的目标（jsfiddle）

问题

2 个答案: