webGL编程指南第五章 MultiTexture.html

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：空
上一章节中我们学习texParameteri的使用,这一章节中我们两个图片进行混合
html 复制代码
<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport">
    <title>Document</title>
    <style>
        #canvas {
            width: 100vw;
            height: 100vw;
            border: 1px solid greenyellow;
        }
    </style>
</head>

<body>
    !!!!!需要指出的是要选择当前文件夹下的sky.jpg!!!!!!
    <!-- <input type="file" accept="image/*" onchange="loadFile(event)"> -->
    <input type="file" onchange="loadFile(event)">
    <canvas id="canvas"></canvas>
    <script>
        let imgSrc = 'https://p2.music.126.net/UrFqYFILx5wBDx-dsIz15A==/109951163025047288.jpg?param=256y256';
        let jpgImgSrc = 'https://p1.music.126.net/LOTxqRjFm03VJEOHJbUqMw==/109951165944804127.jpg?param=256y256';
        // let jpgImgSrc = 'https://img-blog.csdnimg.cn/361654c6611d49bebab085509bd6a244.jpeg';
        // let gifImagSrc = 'https://img-blog.csdnimg.cn/04f072cdb3934051a505a54a4d6f46ed.gif';
        let vexterSource = `
        precision mediump float;
        attribute vec4 a_Position;
        attribute vec2 a_TexCoord;
        varying   vec2 v_TexCoord;
        void main(){
            gl_Position = a_Position;//顶点坐标
            v_TexCoord = a_TexCoord;//纹理坐标系下的坐标
        }
    `
        let fragmentSource = `
            precision mediump float;
            uniform sampler2D u_Sampler0;//纹理
            uniform sampler2D u_Sampler1;//纹理
            varying vec2      v_TexCoord;//纹理坐标系下的坐标
            void main(){
                vec4 color0 = texture2D(u_Sampler0,v_TexCoord);
                vec4 color1 = texture2D(u_Sampler1,v_TexCoord);

                gl_FragColor = color0 * color1; 
            }
        ` 
        let canvas = document.getElementById('canvas');
        let gl = canvas.getContext('webgl');

        //创建顶点着色器
        let vertextShader = gl.createShader(gl.VERTEX_SHADER);
        //给顶点着色器赋值
        gl.shaderSource(vertextShader, vexterSource);
        //编译顶点着色器
        gl.compileShader(vertextShader);

        //创建片元着色器
        let fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
        //给片元着色器赋值
        gl.shaderSource(fragmentShader, fragmentSource)
        //编译片元着色器
        gl.compileShader(fragmentShader)
        //检测着色器创建是否正确
        if (!gl.getShaderParameter(fragmentShader, gl.COMPILE_STATUS)) {
            alert(gl.getShaderInfoLog(fragmentShader));
        }
        //创建程序
        let program = gl.createProgram();
        //给程序赋值
        gl.attachShader(program, vertextShader);
        gl.attachShader(program, fragmentShader);
        //连接程序
        gl.linkProgram(program);
        //使用此着色器
        gl.useProgram(program);


        //变量的处理
        //获取顶点着色器中的变量a_Position
        let a_Position = gl.getAttribLocation(program, 'a_Position');
        //获取顶点着色器中的变量a_TexCoord
        let a_TexCoord = gl.getAttribLocation(program, 'a_TexCoord');
        //获取片元着色器中的变量u_Sampler
        let u_Sampler0 = gl.getUniformLocation(program, 'u_Sampler0');
        //获取片元着色器中的变量u_Sampler
        let u_Sampler1 = gl.getUniformLocation(program, 'u_Sampler1');
        //顶点坐标与纹理坐标
        let vertexTexCoords = new Float32Array([
            -0.5, 0.5, 0.0, 1.0,
            -0.5, -0.5, 0.0, 0.0,
            0.5, 0.5, 1.0, 1.0,
            0.5, -0.5, 1.0, 0.0,
        ])
        let f32Seize = vertexTexCoords.BYTES_PER_ELEMENT;
        //给定点设置坐标 几何图形与纹理的坐标
        let vertexBuffer = gl.createBuffer();
        //绑定buffer
        gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
        //绑定数据
        gl.bufferData(gl.ARRAY_BUFFER, vertexTexCoords, gl.STATIC_DRAW);
        //给a_Position赋值
        gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, f32Seize * 4, 0);
        //使用此变量
        gl.enableVertexAttribArray(a_Position);
        //纹理坐标
        let texCoordBuffer = gl.createBuffer();
        //绑定buffer
        gl.bindBuffer(gl.ARRAY_BUFFER, texCoordBuffer);
        //绑定数据
        gl.bufferData(gl.ARRAY_BUFFER, vertexTexCoords, gl.STATIC_DRAW);
        //给a_TexCoord赋值
        gl.vertexAttribPointer(a_TexCoord, 2, gl.FLOAT, false, f32Seize * 4, f32Seize * 2);
        //使用此变量
        gl.enableVertexAttribArray(a_TexCoord);

        gl.clearColor(0, 0, 0, 1.0);
        //获取图片的素材  
        getImage(imgSrc, u_Sampler1, gl.TEXTURE0, 0);
        getImage(jpgImgSrc, u_Sampler1, gl.TEXTURE1, 1);
        function getImage(imgYrl, u_Sampler, TEXTURE, num) {
            // 文件里的文本会在这里被打印出来 
            let img = new Image();
            img.src = imgYrl;
            img.crossOrigin = ""
            img.onload = () => {
                let texture = gl.createTexture();
                showImage(texture, img, u_Sampler, TEXTURE, num)
                document.body.appendChild(img)
            }
        }
        function showImage(texture, img, u_Sampler, TEXTURE, texUnit) {
            console.log(texture, img, u_Sampler, TEXTURE, texUnit)
            document.body.appendChild(img)
            gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, 1);
            //开始0号纹理通道
            gl.activeTexture(TEXTURE); 
             //想目标绑定纹理对象
             gl.bindTexture(gl.TEXTURE_2D, texture);
            //配置纹理的参数
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.MIRRORED_REPEAT);
            //设置着色器参数
            gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, gl.RGB, gl.UNSIGNED_BYTE, img);
            //设置纹理数据
            gl.uniform1i(u_Sampler, texUnit)
            gl.clear(gl.COLOR_BUFFER_BIT);
            gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4)
        }
    </script>
</body>

</html>
webGL编程指南 第五章 MultiTexture.html

webGL编程指南第五章 MultiTexture.html
