WebGL画点程序v1

本文程序实现画一个点的任务，如下图。其中，点的位置直接给定（“硬编码”）在顶点着色器中。

整个程序包含两个文件，分别是：

1. HelloPoint1.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

<html>

    <head>

        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

        <title>画一个点</title>

    </head>

    <body onload="startup()">

        <canvas id="myGLCanvas" width="640" height="480">

        </canvas>

    </body>

    <script type="text/javascript" src="HelloPoint1.js">

    </script>

</html>

2. HelloPoint1.js

var gl;

function createGLContext(canvas) {

  var names = ["webgl", "experimental-webgl"];

  var context = null;

  for (var i=0; i < names.length; i++) {

    try {

      context = canvas.getContext(names[i]); //获取webgl context绘图上下文

    } catch(e) {}

    if (context) {

      break;

    }

  }

  if (context) {

    context.viewportWidth = canvas.width;

    context.viewportHeight = canvas.height;

  } else {

    alert("Failed to create WebGL context!");

  }

  return context;

}

function loadShader(type, shaderSource) {

  var shader = gl.createShader(type);

  gl.shaderSource(shader, shaderSource);

  gl.compileShader(shader);

  if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {

      alert("Error compiling shader" + gl.getShaderInfoLog(shader));

      gl.deleteShader(shader);

      return null;

  }

  return shader;

}

function setupShaders() {

    //顶点着色器程序

    var vertexShaderSource = 'void main(){ \n' +

    '    gl_Position = vec4(0.0, 0.0, 0.0, 1.0); \n' + //gl_Position指定了点的位置

    '    gl_PointSize = 10.0; \n' +

    '} \n';

    //片元着色器程序

    var fragmentShaderSource = 'void main(){ \n' +

    '    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0); \n' + //gl_FragColor指定像素的颜色

    '} \n';                                         

  var vertexShader = loadShader(gl.VERTEX_SHADER, vertexShaderSource);

  var fragmentShader = loadShader(gl.FRAGMENT_SHADER, fragmentShaderSource);

  var shaderProgram = gl.createProgram();

  gl.attachShader(shaderProgram, vertexShader);

  gl.attachShader(shaderProgram, fragmentShader);

  gl.linkProgram(shaderProgram);

  if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {

    alert("Failed to setup shaders");

  }

  gl.useProgram(shaderProgram);

  gl.program= shaderProgram;

}

function startup(){

    var canvas = document.getElementById('myGLCanvas');//获取<canvas>元素

    gl = createGLContext(canvas);

    setupShaders(); 

    gl.clearColor(0.0, 0.0, 0.0, 1.0);//指定清空<canvas>的颜色

    gl.clear(gl.COLOR_BUFFER_BIT);//清空<canvas>

    gl.drawArrays(gl.POINTS, 0, 1);//从第0个元素开始，在指定位置（gl_Position）画1个点

 }

参考代码

Hello Point——WebGL, http://www.cnblogs.com/idealer3d/p/3513838.html
Professional WebGL Programming: Developing 3D Graphics for the Web,Listing 2-1,http://media.wiley.com/product_ancillary/60/11199688/DOWNLOAD/Listing-2-1.html

转载请注明出处：http://www.cnblogs.com/opengl/p/7262596.html

巴特西

WebGL画点程序v1

1. HelloPoint1.html

2. HelloPoint1.js

参考代码

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