使用WebGL实现一个Viewer来显示STL文件
关键字：WebGL，STL，ThreeJS，Chrome，Viewer，Python3.4， HTML5，Canvas。
OS：Windows 10。
本文介绍如何使用ThreeJS来实现一个WebGL的Viewer，用来浏览STL文件。
STL 文件是在计算机图形应用系统中，用于表示三角形网格的一种文件格式。 它的文件格式非常简单， 应用很广泛。
STL是最多 快速原型系统所应用的标准文件类型。STL是用三角网格来表现3D CAD模型。
1.新建一个STL.html文件如下：
<!DOCTYPE html> <html lang="en"> <head> <title>WebViewer - STL</title> <meta charset="utf-8"> </head> <body> <script src="threejs/three.min.js"></script> <script src="threejs/loaders/STLLoader.js"></script> <script src="threejs/OrbitControls.js"></script> <script> var container; var camera, cameraTarget, scene, renderer; var cameraType = 1; var perspectiveAngle = 45; var cameraPosX = 200; var cameraPosY = 200; var cameraPosZ = 200; var cameraTargetX = 0; var cameraTargetY = 0; var cameraTargetZ = 0; var upVectorX = 0; var upVectorY = 1; var upVectorZ = 0; var cameralScale = 5; init(); animate(); function getQueryStringByName(name){ var result = location.search.match(new RegExp("[\?\&]" + name+ "=([^\&]+)","i")); if(result == null || result.length < 1){ return ""; } return result[1]; } function init() { container = document.createElement( 'div' ); document.body.appendChild( container ); // set camera var cameraTypeStr = getQueryStringByName('cameraType'); cameraType = cameraTypeStr == "" ? cameraType : parseInt(cameraTypeStr); var perspectiveAngleStr = getQueryStringByName('perspectiveAngle'); perspectiveAngle = perspectiveAngleStr == "" ? perspectiveAngle : parseFloat(perspectiveAngleStr); var cameraPosXStr = getQueryStringByName('cameraPosX'); cameraPosX = cameraPosXStr == "" ? cameraPosX : parseFloat(cameraPosXStr) * cameralScale; var cameraPosYStr = getQueryStringByName('cameraPosY'); cameraPosY = cameraPosYStr == "" ? cameraPosY : parseFloat(cameraPosYStr) * cameralScale; var cameraPosZStr = getQueryStringByName('cameraPosZ'); cameraPosZ = cameraPosZStr == "" ? cameraPosZ : parseFloat(cameraPosZStr) * cameralScale; var cameraTargetXStr = getQueryStringByName('cameraTargetX'); cameraTargetX = cameraTargetXStr == "" ? cameraTargetX : parseFloat(cameraTargetXStr) * cameralScale; var cameraTargetYStr = getQueryStringByName('cameraTargetY'); cameraTargetY = cameraTargetYStr == "" ? cameraTargetY : parseFloat(cameraTargetYStr) * cameralScale; var cameraTargetZStr = getQueryStringByName('cameraTargetZ'); cameraTargetZ = cameraTargetZStr == "" ? cameraTargetZ : parseFloat(cameraTargetZStr) * cameralScale; var upVectorXStr = getQueryStringByName('upVectorX'); upVectorX = upVectorXStr == "" ? upVectorX : parseFloat(upVectorXStr) * cameralScale; var upVectorYStr = getQueryStringByName('upVectorY'); upVectorY = upVectorYStr == "" ? upVectorY : parseFloat(upVectorYStr) * cameralScale; var upVectorZStr = getQueryStringByName('upVectorZ'); upVectorZ = upVectorZStr == "" ? upVectorZ : parseFloat(upVectorZStr) * cameralScale; if(cameraType == 0) { camera = new THREE.OrthographicCamera( window.innerWidth / - 2, window.innerWidth / 2, window.innerHeight / 2, window.innerHeight / - 2, 1, 10000 ); } else { camera = new THREE.PerspectiveCamera( perspectiveAngle, window.innerWidth / window.innerHeight, 1, 10000 ); } camera.position.set( cameraPosX, cameraPosY, cameraPosZ); camera.up.set(upVectorX, upVectorY, upVectorZ); cameraTarget = new THREE.Vector3( cameraTargetX, cameraTargetY, cameraTargetZ ); camera.lookAt( cameraTarget ); scene = new THREE.Scene(); scene.fog = new THREE.Fog( 0xffffff, 1, 10000 ); // load file var loader = new THREE.STLLoader(); var modelName = getQueryStringByName('modelName'); loader.load( '../Models/' + modelName, function ( geometry ) { var material = new THREE.MeshPhongMaterial( { color: 0x808080, specular: 0x111111, shininess: 200 } ); var mesh = new THREE.Mesh( geometry, material ); mesh.castShadow = true; mesh.receiveShadow = true; scene.add( mesh ); } ); // lights scene.add( new THREE.AmbientLight( 0x333333 ) ); addDirectionalLight(-1, 1, 1, 0xFFFFFF, 1.35); addDirectionalLight(1, -1, -1, 0xFFFFFF, 1); // renderer renderer = new THREE.WebGLRenderer( { antialias: true } ); renderer.setClearColor( scene.fog.color ); renderer.setSize( window.innerWidth, window.innerHeight ); renderer.gammaInput = true; renderer.gammaOutput = true; renderer.shadowMapEnabled = true; renderer.shadowMapCullFace = THREE.CullFaceBack; container.appendChild( renderer.domElement ); // orbit control control = new THREE.OrbitControls( camera, renderer.domElement ); // events window.addEventListener( 'resize', onWindowResize, false ); } function addDirectionalLight( x, y, z, color, intensity ) { var directionalLight = new THREE.DirectionalLight( color, intensity ); directionalLight.position.set( x, y, z ) scene.add( directionalLight ); } function onWindowResize() { camera.aspect = window.innerWidth / window.innerHeight; camera.updateProjectionMatrix(); renderer.setSize( window.innerWidth, window.innerHeight ); } function animate() { requestAnimationFrame( animate ); render(); } function render() { // var timer = Date.now() * 0.0005; // // camera.position.x = Math.cos( timer ) * 3; // camera.position.z = Math.sin( timer ) * 3; renderer.render( scene, camera ); } </script> </body> </html>
2.直接用Chrome打开文件STL.html，将会看到一下错误，那是因为不能打开本地模型文件，需要创建一个http server。
XMLHttpRequest cannot load file:///D:/L/Dev/WebViewer/Models/. Cross origin requests are only supported for protocol schemes: http, data, chrome, chrome-extension, https, chrome-extension-resource.THREE.XHRLoader.load @ three.min.js:258
three.min.js:258 Uncaught NetworkError: Failed to execute 'send' on 'XMLHttpRequest': Failed to load 'file:///D:/L/Dev/WebViewer/Models/'.
3.本文使用python来创建一个http server，新建localServer.py文件，内容如下：
from threading import Thread import webbrowser, http.server, socketserver import time; port_number = 8000 server = None def startServer(port): Handler = http.server.SimpleHTTPRequestHandler global server server = socketserver.TCPServer(("", port), Handler) print("Start server at port", port) server.serve_forever() def start(port): thread = Thread(target=startServer, args=[port]) thread.start() startTime = int(time.time()) while not server: if int(time.time()) > startTime + 60: print("Time out") break return server def stop(): if server: server.shutdown() def openUrl(): url = "http://localhost:" + str(port_number) webbrowser.open(url) print(url + " is opened in browser") if __name__ == "__main__": start(port_number) openUrl()
4.文件夹结构如下：
Models - 模型文件夹，放置模型文件，例如bike_frame.stl。
threejs - threejs文件夹，放置threejs相关的库文件
5. 双击运行LocalServer.py启动一个http服务器。
6.在Chrome里面打开http://localhost:8000/WebGLViewer/STL.html?modelName=bike_frame.stl，如下图。
源代码地址：https://github.com/ldlchina/Sample-of-WebGL-with-STL-loader
相关链接: http://threejs.org/