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webGL编程指南第五章 MultiAttributeSize

article 2024/9/24 19:20:58

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

本章节中我我们学习使用buffer传递数据

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>

    <canvas id='canvas'></canvas>
    <script>
        let canvas = document.getElementById('canvas');
        let gl = canvas.getContext('webgl');
        //顶点着色器
        let vertexShaderSource = `
            attribute vec2 a_Position;
            attribute float a_PointSize;
            void main(){
                gl_Position = vec4(a_Position,0.0,1.0) ;
                gl_PointSize = a_PointSize;
            }
        `
        //片元着色器
        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);
        gl.shaderSource(vertexShader, vertexShaderSource)
        gl.compileShader(vertexShader)
        //创建片元着色器
        let fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
        gl.shaderSource(fragmentShader, fragmentShaderSouce)
        gl.compileShader(fragmentShader)
        //创建渲染程序
        let program = gl.createProgram();
        gl.attachShader(program, vertexShader);
        gl.attachShader(program, fragmentShader);
        gl.linkProgram(program);
        //使用当前渲染程序
        gl.useProgram(program)


        //检查片元着色器的是否正确
        if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
            throw gl.getProgramInfoLog(program);
        }
        //三角形的坐标
        let positonArray = new Float32Array([
            0.5, 0.5,
            -0.5, -0.5, 
            0.5, -0.5, 
            -0.5, 0.5])
        //每个坐标点但的大小
        let sizeArray = new Float32Array([10.0, 20.0, 30.0,40.0])
        //位置坐标变量
        let a_Position = gl.getAttribLocation(program, 'a_Position');
        //点的大小
        let a_PointSize = gl.getAttribLocation(program, 'a_PointSize')

        //创建坐标的buffer
        let buffer = gl.createBuffer();
        //绑定buffer
        gl.bindBuffer(gl.ARRAY_BUFFER, buffer)
        //将三角形的坐标数据放入缓冲区
        gl.bufferData(gl.ARRAY_BUFFER, positonArray, gl.STATIC_DRAW) 
        // a_Position 赋值
        gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);
        // 使能顶点位置
        gl.enableVertexAttribArray(a_Position);

        //创建顶点大小的buffer
        let pointSizeBuffer = gl.createBuffer();
        //绑定buffer
        gl.bindBuffer(gl.ARRAY_BUFFER, pointSizeBuffer);
        // 将点的大小数据放入缓冲区
        gl.bufferData(gl.ARRAY_BUFFER,sizeArray,gl.STATIC_DRAW);
        // a_PointSize 赋值
        gl.vertexAttribPointer(a_PointSize, 1, gl.FLOAT, false, 0, 0)
        // 使能顶点大小
        gl.enableVertexAttribArray(a_PointSize);
        //绘制
        gl.clearColor(0.0, 0.0, 0.0, 1.0);
        gl.clear(gl.COLOR_BUFFER_BIT);
        //绘制点  从第0个开始，绘制4次
        gl.drawArrays(gl.POINTS, 0, 4)

    </script>
</body>

</html>

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