webGL编程指南 第三章 旋转三角形
我会持续更新关于wegl的编程指南中的代码。
当前的代码不会使用书中的缩写，每一步都是会展开写。希望能给后来学习的一些帮助
git代码地址
接着 上一节 接着做平移的转化。本案例是三角形的旋转
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</head><body><h3>可以按下按键ADSW</h3><p>旋转的角度：<span id="num"></span></p><canvas id='canvas'></canvas><script>let canvas = document.getElementById('canvas');let gl = canvas.getContext('webgl');let vertexShaderSource = `attribute vec2 a_Position;uniform float u_CosB,u_SinB; void main(){gl_Position.x = a_Position.x * u_CosB - a_Position.y*u_SinB;gl_Position.y = a_Position.x * u_SinB + a_Position.y*u_CosB;gl_Position.z = 0.0;gl_Position.w = 1.0;}`let fragmentShaderSouce = `precision mediump float;void main(){gl_FragColor = vec4(1.0,0.0,0.0,1.0);}`// 创建顶点着色器let vertexShader = gl.createShader(gl.VERTEX_SHADER);// 设置着色器源代码gl.shaderSource(vertexShader, vertexShaderSource)// 编译着色器gl.compileShader(vertexShader)// 创建着片元色器let fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);// 设置着色器源代码gl.shaderSource(fragmentShader, fragmentShaderSouce)// 编译着色器gl.compileShader(fragmentShader)//创建渲染程序let program = gl.createProgram();// 把顶点着色器添加到渲染程序gl.attachShader(program, vertexShader);gl.attachShader(program, fragmentShader);gl.linkProgram(program);//使用当前渲染程序gl.useProgram(program)//检测着色器链接是否正确if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {throw gl.getProgramInfoLog(program);} //x抽的旋转角度let rotateX = 0.0;//y轴的旋转角度let rotateY = 0;//三角的三个顶点的坐标位置let positonArray = new Float32Array([0.0, 0.5, -0.5, -0.5, 0.5, -0.5]);// 获取顶点着色器的变量let a_Position = gl.getAttribLocation(program, 'a_Position');// 获取旋转角度的变量let u_CosB = gl.getUniformLocation(program, 'u_CosB')let u_SinB = gl.getUniformLocation(program, 'u_SinB')// 创建缓冲区let buffer = gl.createBuffer();//将缓冲区对象绑定到目标gl.bindBuffer(gl.ARRAY_BUFFER, buffer);//向缓冲区写入数据gl.bufferData(gl.ARRAY_BUFFER, positonArray, gl.STATIC_DRAW)//将缓冲区对象绑定到目标gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0)// 启用变量a_Positiongl.enableVertexAttribArray(a_Position);//绘制gl.clearColor(0.0, 0.0, 0.0, 1.0);const render = function () {//赋值x角度gl.uniform1f(u_CosB, Math.cos(Math.PI*rotateX/180.0));//赋值y角度gl.uniform1f(u_SinB, Math.sin(Math.PI*rotateX/180.0));// 清空画布gl.clear(gl.COLOR_BUFFER_BIT);// 绘制三角形gl.drawArrays(gl.TRIANGLES, 0, 3)setNumer()}render()document.onkeydown = function (e) { //对整个页面监听 var keyNum = window.event ? e.keyCode : e.which; //获取被按下的键值 //判断如果用户按下了回车键（keycody=13） if (keyNum == 65) {console.log('A');rotateX -= 1; rotateY=0render()}//判断如果用户按下了空格键(keycode=32)， if (keyNum == 68) {console.log('D');rotateX +=1; rotateY=0render()}//判断如果用户按下了空格键(keycode=32)， if (keyNum == 83) {console.log('S');rotateY -= 1; rotateX=0render()}//判断如果用户按下了空格键(keycode=32)， if (keyNum == 87) {console.log('W');rotateY += 1; rotateX=0render();}}function setNumer (){let text = document.getElementById('num');text.innerText = `rotateX:${ rotateX}`} </script>
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