https://blog.csdn.net/qq563969790/article/details/76584976
网上资料大部分是通过引入外部font库进行文字效果的载入，但是在实际运行的时候发现非常占用资源。于是不得不想另一种方法。
于是想到了three.js中的粒子系统。这当中有个很gay的骚操作是下面这个函数。
var particleMaterial = new THREE.SpriteCanvasMaterial( {
color: 0x000000,
program: function ( context ) {
context.beginPath();
context.font="bold 20px Arial";
context.fillStyle="#058";
context.transform(-1,0,0,1,0,0);
context.rotate(Math.PI);
context.fillText( wordFont , 0, 0 );
}
上面的函数当中，可以传入一个canvas对象。恩，对。如果你想载入文字，写到canvas里就够啦，你还可以画小h图哦。
附上源代码：
ps:代码中最后的注释部分是外部加载字体的方式。有知道的大神请告诉我这么loader为啥贼卡。还有为什么context中文字fillText初始是镜像倒转的？又费了一点劲给它倒腾回来。可能涉及到坐标的原因，同样希望大神告知。
<!DOCTYPE html>
<html lang="en">
<head>
<title>three.js measute_length</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: Arial;
margin: 0px;
overflow: hidden;
}
</style>
</head>
<body>
<script src="js/three.js"></script>
<script src="js/Projector.js"></script>
<script src="js/CanvasRenderer.js"></script>
<script src="js/OrbitControls.js"></script>
<script src="js/stats.min.js"></script>
<script>
var container, stats;
var camera, scene, renderer;
var particleMaterial;
var raycaster;
var mouse;
var objects = [];
var points = [];
init();
animate();
function init() {
container = document.createElement( 'div' );
document.body.appendChild( container );
camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 1, 10000 );
camera.position.set( 0, 400, 700 );
scene = new THREE.Scene();
var geometry = new THREE.BoxGeometry( 100, 100, 100 );
for ( var i = 0; i < 10; i ++ ) {
var object = new THREE.Mesh( geometry, new THREE.MeshBasicMaterial( { color: Math.random() * 0xffffff, opacity: 0.5 } ) );
object.position.x = Math.random() * 800 - 400;
object.position.y = Math.random() * 800 - 400;
object.position.z = Math.random() * 800 - 400;
object.scale.x = Math.random() * 2 + 1;
object.scale.y = Math.random() * 2 + 1;
object.scale.z = Math.random() * 2 + 1;
object.rotation.x = Math.random() * 2 * Math.PI;
object.rotation.y = Math.random() * 2 * Math.PI;
object.rotation.z = Math.random() * 2 * Math.PI;
scene.add( object );
objects.push( object );
}
var PI2 = Math.PI * 2;
particleMaterial = new THREE.SpriteCanvasMaterial( {
color: 0x000000,
program: function ( context ) {
context.beginPath();
context.arc( 0, 0, 0.5, 0, PI2, true );
context.fill();
}
} );
raycaster = new THREE.Raycaster();
mouse = new THREE.Vector2();
renderer = new THREE.CanvasRenderer();
renderer.setClearColor( 0xf0f0f0 );
renderer.setPixelRatio( window.devicePixelRatio );
renderer.setSize( window.innerWidth, window.innerHeight );
container.appendChild( renderer.domElement );
stats = new Stats();
container.appendChild( stats.dom );
document.addEventListener( 'mousedown', onDocumentMouseDown, false );
document.addEventListener( 'touchstart', onDocumentTouchStart, false );
window.addEventListener( 'resize', onWindowResize, false );
var controls = new THREE.OrbitControls(camera); //camera control
controls.addEventListener('change', render);
}
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
renderer.setSize( window.innerWidth, window.innerHeight );
}
function onDocumentTouchStart( event ) {
event.preventDefault();
event.clientX = event.touches[0].clientX;
event.clientY = event.touches[0].clientY;
onDocumentMouseDown( event );
}
function onDocumentMouseDown( event ) {
event.preventDefault();
mouse.x = ( event.clientX / renderer.domElement.clientWidth ) * 2 - 1;
mouse.y = - ( event.clientY / renderer.domElement.clientHeight ) * 2 + 1;
raycaster.setFromCamera( mouse, camera );
//射线原理拾取目标
var intersects = raycaster.intersectObjects( objects );
if ( intersects.length > 0 ) {
//创建粒子，便于标识点击位置
var particle = new THREE.Sprite( particleMaterial );
particle.position.copy( intersects[ 0 ].point );
particle.scale.x = particle.scale.y = 1;
scene.add( particle );
//保存选中点
points.push( intersects[ 0 ].point );
if( points.length >1 ) {
var p2 = points[points.length-1];
var p1 = points[points.length-2];
//动画的形式画线
drawLine( p1, p2);
}
}
}
function animate() {
requestAnimationFrame( animate );
render();
stats.update();
}
function render() {
renderer.render( scene, camera );
}
function drawLine( p1, p2) {
var directionVector = new THREE.Vector3();
var p3 = new THREE.Vector3();
directionVector.x = p2.x - p1.x;
directionVector.y = p2.y - p1.y;
directionVector.z = p2.z - p1.z;
var length = Math.sqrt( directionVector.x * directionVector.x
+ directionVector.y * directionVector.y
+ directionVector.z * directionVector.z);
var text = Math.round( length ) + "m";
var flag = 1;
var id = setInterval(function () {
if (flag == 11) {
clearInterval(id);
flag = 1;
} else {
var geometry = new THREE.Geometry();
var material = new THREE.LineBasicMaterial( { opacity:1,color:0x000000 } );
geometry.vertices.push(p1);
p3.x = p1.x + (directionVector.x/10) * flag;
p3.y = p1.y + (directionVector.y/10) * flag;
p3.z = p1.z + (directionVector.z/10) * flag;
geometry.vertices.push(p1);
geometry.vertices.push(p3);
var geo = new THREE.Line(geometry, material);
scene.add(geo);
flag++;
}
}, 10);
initText( text, p2 );
}
// var font;
// var loader = new THREE.FontLoader();
// loader.load('js/optimer_bold.typeface.json',function(response) {
// font = response;
// });
function initText( wordFont, p1){
var particleMaterial = new THREE.SpriteCanvasMaterial( {
color: 0x000000,
program: function ( context ) {
context.beginPath();
context.font="bold 20px Arial";
context.fillStyle="#058";
context.transform(-1,0,0,1,0,0);
context.rotate(Math.PI);
context.fillText( wordFont , 0, 0 );
}
} );
var particle = new THREE.Sprite( particleMaterial );
particle.position.copy( p1 );
particle.rotation.x = Math.PI/2;
// particle.lookAt( camera );
scene.add( particle );
// var textGeometry = new THREE.TextGeometry(wordFont,{
// "font": font,
// "size" : 10,
// "height" : 0,
// "color" : 0x000000
// })
//
// var text = new THREE.Mesh( textGeometry, new THREE.MeshBasicMaterial( { color: 0x000000 } ) );
//
//
// text.position.x = p1.x + 2;
// text.position.y = p1.y + 2;
// text.position.z = p1.z + 2;
// text.lookAt(camera.position);
// scene.add(text);
}
</script>
</body>
</html>
效果如下：
用到threejs的 精灵材料（SpriteMaterial）
https://threejs.org/docs/index.html#api/zh/materials/SpriteMaterial
下面的属性可以帮助我们实现文字在屏幕上大小不随像机位置变化而放缩！
.sizeAttenuation : Boolean ----标识文字是否自动放缩（false为屏幕尺寸自动放缩）
精灵的大小是否会被相机深度衰减。（仅限透视摄像头。）默认为true。