强制 OrbitControls 在移动对象周围导航（几乎可以工作）

Question

我正在学习 Three.js 并且我正在玩太阳系模型以了解它是如何工作的。所以我有一个场景，其中地球围绕太阳旋转，月球围绕地球旋转。

现在我想专注于月球并使用控件围绕它旋转（同时让它始终位于屏幕中央）。OrbitControls 似乎是理想的选择，但我无法让它们与移动的月亮一起工作。

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);

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;
}

结果：它很好地将月亮置于中心，但显然您无法导航场景，因为我还没有工作OrbitControls。但这种尝试可以作为参考。

尝试 2 - 添加 OrbitControls ( jsfiddle )

然后我加了OrbitControls。

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/109/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>

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;
}

结果：月亮从中心移到了一边（不知道为什么？）。当您开始使用鼠标导航时，一切都会变得疯狂。效果就像OrbitControls围绕场景中心和相机围绕其父级（月球）导航。实际上，它们不会以一致的方式改变状态，一切都会变得疯狂。

尝试 3 - 控制轨道的目标 ( jsfiddle )

我尝试的最后一个选项是强制设置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();

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/109/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>

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);
}

结果：最初月亮位于屏幕的一侧（与第二次尝试中的位置相同），但是当您开始导航时，月亮“跳”到屏幕中央，您可以在它周围导航。几乎完美。只要你不放大。当您放大/缩小时，您会开始看到月亮在放大操作期间旋转。

问题

1. 为什么不OrbitControls尊重相机的父节点是月球的事实，并不断围绕场景中心导航？
2. 为什么月亮在添加后“跳”到了屏幕的一边OrbitControls？
3. 让它工作的优雅方式是什么？（target由于缩放问题，强制循环跟踪月球既不优雅也不工作）？

河 98

编辑：编辑更改以使句子更清晰。 编辑：升级到three.js r。109.

Answer 1

我通过引入一个假相机使它工作，它与原始相机具有相同的一切，除了 camera.parent

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

这种方式OrbitControls有一个带有自己坐标系的相机。

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();

它运作良好。

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);

（以下代码已相应更新）

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

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

render();

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