88 lines
3.0 KiB
HTML
88 lines
3.0 KiB
HTML
<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<title>使用WebGL绘制一个点</title>
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</head>
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<body>
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<!--canvas标签创建一个宽高均为500像素，背景为蓝色的矩形画布-->
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<canvas id="webgl" width="500" height="500" style="background-color: blue"></canvas>
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<script id="vertexShader" type="x-shader/x-vertex">
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//attribute声明vec4类型变量apos
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attribute vec4 apos;
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void main() {
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//顶点坐标apos赋值给内置变量gl_Position
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//逐顶点处理数据
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gl_Position = apos;
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}
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</script>
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<!-- 片元着色器源码 -->
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<script id="fragmentShader" type="x-shader/x-fragment">
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void main() {
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// 逐片元处理数据，所有片元(像素)设置为红色
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gl_FragColor = vec4(1.0,0.0,0.0,1.0);
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}
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</script>
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<script>
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//通过getElementById()方法获取canvas画布
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var canvas=document.getElementById('webgl');
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//通过方法getContext()获取WebGL上下文
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var gl=canvas.getContext('webgl');
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//初始化着色器
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var vertexShaderSource = document.getElementById('vertexShader').innerText;
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//片元着色器源码
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var fragShaderSource = document.getElementById('fragmentShader').innerText;
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//初始化着色器
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var program = initShader(gl,vertexShaderSource,fragShaderSource);
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//开始绘制，显示器显示结果
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//获取顶点着色器的位置变量apos，即aposLocation指向apos变量。
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var aposLocation = gl.getAttribLocation(program,'apos');
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var data=new Float32Array([0.5,0.5,-0.5,0.5,-0.5,-0.5,0.5,-0.5]);
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//创建缓冲区对象
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var buffer=gl.createBuffer();
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//绑定缓冲区对象,激活buffer
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gl.bindBuffer(gl.ARRAY_BUFFER,buffer);
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//顶点数组data数据传入缓冲区
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gl.bufferData(gl.ARRAY_BUFFER,data,gl.STATIC_DRAW);
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//缓冲区中的数据按照一定的规律传递给位置变量apos
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gl.vertexAttribPointer(aposLocation,2,gl.FLOAT,false,0,0);
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//允许数据传递
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gl.enableVertexAttribArray(aposLocation);
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gl.drawArrays(gl.TRIANGLES,0,4);
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//声明初始化着色器函数
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function initShader(gl,vertexShaderSource,fragmentShaderSource){
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//创建顶点着色器对象
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var vertexShader = gl.createShader(gl.VERTEX_SHADER);
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//创建片元着色器对象
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var fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
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//引入顶点、片元着色器源代码
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gl.shaderSource(vertexShader,vertexShaderSource);
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gl.shaderSource(fragmentShader,fragmentShaderSource);
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//编译顶点、片元着色器
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gl.compileShader(vertexShader);
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gl.compileShader(fragmentShader);
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//创建程序对象program
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var program = gl.createProgram();
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//附着顶点着色器和片元着色器到program
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gl.attachShader(program,vertexShader);
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gl.attachShader(program,fragmentShader);
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//链接program
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gl.linkProgram(program);
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//使用program
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gl.useProgram(program);
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//返回程序program对象
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return program;
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}
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</script>
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</body>
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</html> |