下面的脚本无法正常工作。（它只需要 jquery 和 three.js 即可运行）。麻烦的线是这两条：
// change the view so looking at the top of the airplane
views[1].camera.position.set( 0,5,0 );
views[1].camera.lookAt(objectManager.airplane.position);
奇怪的是，如果将这两行注释掉，可以看出下面两行类似的前面的行确实按预期运行：
views[1].camera.lookAt(objectManager.airplane.position);
和
view.camera.position.set( 5,0,0 );
由于某种原因，对 camera.lookAt 的调用似乎只在第一次起作用。之后，相机不再跟随飞机物体。如果有人能弄清楚我做错了什么，我将不胜感激！
完整的脚本如下。
谢谢
$(function(){
var scene, renderer, viewPort, objectManager, views;
init();
animate();
function init() {
viewPort = $('body');
scene = new THREE.Scene();
// construct the two cameras
initialiseViews();
// construct airplane, lights and floor grid
objectManager = new ObjectManager();
objectManager.construct();
objectManager.addToScene(scene);
// make the second camera's position
// stay fixed relative to the airplane
objectManager.airplane.add(views[1].camera);
// make the second camera stay looking
// at the airplane
views[1].camera.lookAt(objectManager.airplane.position);
renderer = new THREE.WebGLRenderer();
renderer.setClearColorHex(0x000000, 1);
renderer.setSize( viewPort.innerWidth(), viewPort.innerHeight() );
viewPort.get(0).appendChild(renderer.domElement);
}
function animate() {
requestAnimationFrame( animate );
render();
}
function render() {
objectManager.tick();
for (var i in views){
views[i].render(scene, renderer);
}
}
function initialiseViews(){
views = [];
// ----------------------------------------------------
// Create the first view, static with respect to ground
// ----------------------------------------------------
views[0] = new View(viewPort, objectManager, scene);
var view = views[0];
view.fov = 40;
view.proportions.height = 0.5;
view.proportions.bottom = 0.5;
view.init();
view.camera.position.y = 1;
view.camera.position.z = 4;
// ----------------------------------------------------
// Create the second view, which follows the airplane
// ----------------------------------------------------
views[1] = new View(viewPort, objectManager, scene);
var view = views[1];
view.fov = 20;
view.proportions.height = 0.5;
view.init();
// set the initial position of the camera
// with respect to the airplane. Views from behind
view.camera.position.set( 5,0,0 );
view.updateCamera = function(){
// change the view so looking at the top of the airplane
views[1].camera.position.set( 0,5,0 );
views[1].camera.lookAt(objectManager.airplane.position);
views[1].camera.updateProjectionMatrix();
};
}
});
function View(viewport, om, scene){
this.scene = scene;
this.camera;
this.objectManager = om;
this.viewPort = viewport;
this.fov = 30;
// default: full width and height
this.proportions = { left: 0, bottom: 0, height: 1, width: 1 };
this.pixels = { left: 0, bottom: 0, height: 0, width: 0, aspect: 0 };
this.aspect;
this.init = function(){
this.pixels.left = Math.floor(this.proportions.left * this.viewPort.innerWidth());
this.pixels.width = Math.floor(this.proportions.width * this.viewPort.innerWidth());
this.pixels.bottom = Math.floor(this.proportions.bottom * this.viewPort.innerHeight());
this.pixels.height = Math.floor(this.proportions.height * this.viewPort.innerHeight());
this.pixels.aspect = this.pixels.width / this.pixels.height;
this.makeCamera();
};
this.makeCamera = function(){
this.camera = new THREE.PerspectiveCamera(
this.fov,
this.pixels.aspect,
0.1, 10000
);
this.camera.updateProjectionMatrix();
this.scene.add(this.camera);
};
this.render = function(scene, renderer){
this.updateCamera();
pixels = this.pixels;
renderer.setViewport(pixels.left, pixels.bottom, pixels.width, pixels.height);
renderer.setScissor(pixels.left, pixels.bottom, pixels.width, pixels.height);
renderer.enableScissorTest(true);
renderer.render( scene, this.camera );
};
this.updateCamera = function(){};
}
function ObjectManager(){
// manages all visible 3d objects (including lights)
this.airplane;
var grid;
var ambientLight;
var pointLight;
this.construct = function(){
this.constructAirplane();
this.constructLights();
this.constructFloorGrid();
};
this.constructAirplane = function(){
this.airplane = new THREE.Object3D();
var fuselage = newCube(
{x: 1, y: 0.1, z: 0.1},
{x: 0, y: 0, z: 0},
[0xffff00, 0x808000, 0x0000ff, 0xff00000, 0xffffff, 0x808080],
[0, 1, 2, 3, 4, 5]
);
this.airplane.add(fuselage);
var tail = newCube(
{x: 0.15, y: 0.2, z: 0.03},
{x: 0.5, y: 0.199, z: 0},
[0xffff00, 0x808000, 0x0000ff, 0xff00000, 0xffffff, 0x808080],
[0, 1, 2, 3, 4, 5]
);
this.airplane.add(tail);
var wings = newCube(
{x: 0.3, y: 0.05, z: 1},
{x: -0.05, y: 0, z: 0},
[0xffff00, 0x808000, 0x0000ff, 0xff00000, 0xffffff, 0x808080],
[0, 1, 2, 3, 4, 5]
);
this.airplane.add(wings);
};
this.constructLights = function(){
ambientLight = new THREE.AmbientLight(0x808080);
pointLight = new THREE.PointLight(0x808080);
pointLight.position = {x: 100, y: 100, z: 100};
};
this.constructFloorGrid = function(){
grid = new THREE.Object3D();
var geometry = new THREE.Geometry();
geometry.vertices.push(new THREE.Vector3( - 200, 0, 0 ) );
geometry.vertices.push(new THREE.Vector3( 200, 0, 0 ) );
linesMaterial = new THREE.LineBasicMaterial( { color: 0x00ff00, opacity: 1, linewidth: .1 } );
for ( var i = 0; i <= 200; i ++ ) {
var line = new THREE.Line( geometry, linesMaterial );
line.position.z = ( i * 2 ) - 200;
grid.add( line );
var line = new THREE.Line( geometry, linesMaterial );
line.position.x = ( i * 2 ) - 200;
line.rotation.y = 90 * Math.PI / 180;
grid.add( line );
}
};
this.addToScene = function(scene){
scene.add( this.airplane );
scene.add( grid );
scene.add( ambientLight );
scene.add( pointLight );
};
this.tick = function(){
this.airplane.rotation.x += 0.005;
this.airplane.rotation.y += 0.01;
this.airplane.position.x -= 0.05;
};
};
function newCube(dims, pos, cols, colAss){
var mesh;
var geometry;
var materials = [];
geometry = new THREE.CubeGeometry( dims.x, dims.y, dims.z );
for (var i in cols){
materials[i] = new THREE.MeshLambertMaterial( { color: cols[i], ambient: cols[i], overdraw: true } );
}
geometry.materials = materials;
for (var i in colAss){
geometry.faces[i].materialIndex = colAss[i];
}
mesh = new THREE.Mesh( geometry, new THREE.MeshFaceMaterial( materials ) );
mesh.position = pos;
return mesh;
}