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;
background-color: #f0f0f0;
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>
博客才开始写没多久，风格还没统一。先凑合着看呗