webGL编程指南第三章矩阵旋转三角形rotatedTriangle

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：git

接着上一节中接着做平移的转化。在本次的案例案例中主要是xy的坐标变量相加，同时传递个给相关变量

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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 vec4 a_Position;uniform mat4 u_mat4; void main(){gl_Position=u_mat4*a_Position;}`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);// 创建片元着色器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();// 附着顶点着色器和片元着色器到渲染程序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);} // 旋转角度let rotateX = 0.0;let rotateY = 0;// 三角形的顶点let positonArray = new Float32Array([0.0, 0.5, -0.5, -0.5, 0.5, -0.5])// 获取顶点着色器中变量a_Position的存储位置let a_Position = gl.getAttribLocation(program, 'a_Position');// 激活顶点着色器中变量u_mat4的存储位置let u_mat4 = gl.getUniformLocation(program, 'u_mat4');// 创建buffer对象let buffer = gl.createBuffer();// 绑定buffer对象gl.bindBuffer(gl.ARRAY_BUFFER, buffer)// 向buffer中写入数据gl.bufferData(gl.ARRAY_BUFFER, positonArray, gl.STATIC_DRAW)// 设置attribute变量a_Position的值gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0)// 启用attribute变量a_Positiongl.enableVertexAttribArray(a_Position);//绘制gl.clearColor(0.0, 0.0, 0.0, 1.0);const render = function () {// 计算角度let cos = Math.cos(Math.PI*rotateX/180.0);let sin = Math.sin(Math.PI*rotateX/180.0);// 计算旋转矩阵let mate4=new Float32Array([cos,sin,0.0,0.0,-sin,cos,0.0,0.0,0.0,0.0,1.0,0.0,0.0,0.0,0.0,1.0,])// 设置旋转矩阵gl.uniformMatrix4fv(u_mat4, false, mate4)// 清除画布gl.clear(gl.COLOR_BUFFER_BIT);// 绘制图形gl.drawArrays(gl.TRIANGLES, 0, 3)// 更新角度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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