使用 Threejs，我尝试从相机位置到原点画一条线。 我希望该线始终指向屏幕的中间（假设从相机原点查看重新渲染的场景） 但事实并非如此（该线始终指向屏幕的一侧）。 下面的代码是正式的 Threejs webgl_geometry_extrude_shapes.html 示例的子集。 我添加了函数draw_line_from_camera_to_origin（场景，相机）
我做错了什么？
谢谢， 阿夫纳
<!DOCTYPE html>
<html lang="en">
<head>
<title>three.js webgl - geometry - extrude shapes</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
<style>
body {
font-family: Monospace;
background-color: #222;
margin: 0px;
overflow: hidden;
}
a {
color: #f80;
}
</style>
</head>
<body>
<script src="../build/three.js"></script>
<script src="js/controls/TrackballControls.js"></script>
<script>
var container;
var camera, scene, renderer, controls;
init();
animate();
function draw_line_from_camera_to_origin(scene, camera)
{
// Draw line from camera to origin
var pointA2 = new THREE.Vector3( camera.position.x, camera.position.y, camera.position.z );
var pointB2 = new THREE.Vector3( 0, 0, 0 );
var geometry2 = new THREE.Geometry();
geometry2.vertices.push( pointA2 );
geometry2.vertices.push( pointB2 );
var material2 = new THREE.LineBasicMaterial( { color : 'yellow' } );
var line2 = new THREE.Line( geometry2, material2 );
scene.add( line2 );
}
function init() {
var info = document.createElement( 'div' );
info.style.position = 'absolute';
info.style.top = '10px';
info.style.width = '100%';
info.style.textAlign = 'center';
info.style.color = '#fff';
info.style.link = '#f80';
info.innerHTML = '<a href="http://threejs.org" target="_blank" rel="noopener">three.js</a> webgl - geometry extrude shapes';
document.body.appendChild( info );
renderer = new THREE.WebGLRenderer();
renderer.setPixelRatio( window.devicePixelRatio );
renderer.setSize( window.innerWidth, window.innerHeight );
document.body.appendChild( renderer.domElement );
scene = new THREE.Scene();
scene.background = new THREE.Color( 0x222222 );
camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 1, 1000 );
camera.position.set( 0, 0, 500 );
controls = new THREE.TrackballControls( camera, renderer.domElement );
controls.minDistance = 200;
controls.maxDistance = 500;
scene.add( new THREE.AmbientLight( 0x222222 ) );
var light = new THREE.PointLight( 0xffffff );
light.position.copy( camera.position );
scene.add( light );
//
var closedSpline = new THREE.CatmullRomCurve3( [
new THREE.Vector3( -60, -100, 60 ),
new THREE.Vector3( -60, 20, 60 ),
new THREE.Vector3( -60, 120, 60 ),
new THREE.Vector3( 60, 20, -60 ),
new THREE.Vector3( 60, -100, -60 )
] );
closedSpline.curveType = 'catmullrom';
closedSpline.closed = true;
var extrudeSettings = {
steps : 100,
bevelEnabled : false,
extrudePath : closedSpline
};
var pts = [], count = 3;
for ( var i = 0; i < count; i ++ ) {
var l = 20;
var a = 2 * i / count * Math.PI;
pts.push( new THREE.Vector2 ( Math.cos( a ) * l, Math.sin( a ) * l ) );
}
var shape = new THREE.Shape( pts );
var geometry = new THREE.ExtrudeGeometry( shape, extrudeSettings );
var material = new THREE.MeshLambertMaterial( { color: 0xb00000, wireframe: false } );
var mesh = new THREE.Mesh( geometry, material );
scene.add( mesh );
draw_line_from_camera_to_origin(scene, camera);
}
function animate() {
requestAnimationFrame( animate );
controls.update();
renderer.render( scene, camera );
}
</script>
</body>
</html>
您需要更新另一个点的位置。
当你第一次创建这条线时，你告诉它空间中的一个点，它永远不会从那里移动。它可能看起来像是在移动，但这只是因为它是一条很长的线。
所以你需要将 Geometry2 设置为全局变量（位于顶部）：
var camera, scene, renderer, controls, geometry2;
然后在
vardraw_line_from_camera_to_originfunction animate() {
geometry2.vertices[0].x = camera.position.x;
geometry2.vertices[0].y = camera.position.y;
geometry2.vertices[0].z = camera.position.z;
geometry2.verticesNeedUpdate = true;
requestAnimationFrame( animate );
controls.update();
renderer.render( scene, camera );
}
现在，当您移动相机时，您会看到线条随之移动，然后漂移回到相机的位置。我不知道为什么这样做，我实际上希望这条线是不可见的（因为线的宽度为 0，并且它直接指向相机）。