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2021-12-21 webgl实现倒影效果

2021-12-21 webgl实现倒影效果

作者: MrSwilder | 来源:发表于2021-12-21 00:54 被阅读0次
    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Title</title>
    <style>
        body {
            margin: 0;
            overflow: hidden;
        }

        #canvas {
            margin: 0;
            display: block;
        }
    </style>
</head>
<body onload="main()">
<canvas id="canvas" height="800" width="800"></canvas>
</body>
<script src="/lib/webgl-utils.js"></script>
<script src="/lib/webgl-debug.js"></script>
<script src="/lib/cuon-utils.js"></script>
<script src="/lib/cuon-matrix.js"></script>
<script>
    //设置WebGL全屏显示
    var canvas = document.getElementById("canvas");
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;

    //设置顶点着色器
    var vertexShaderSource = "" +
        "attribute vec4 a_Position;\n" +
        "attribute vec2 a_TexCoord;\n" +
        "uniform mat4 u_MvpMatrix;\n" +
        "varying vec2 v_TexCoord;\n" +
        "void main(){\n" +
        "   gl_Position = u_MvpMatrix * a_Position;\n" +
        "   v_TexCoord = a_TexCoord;\n" +
        "}\n";

    //设置片元着色器
    var fragmentShaderSource = "" +
        "#ifdef GL_ES\n" +
        "precision mediump float;\n" +
        "#endif\n" +
        "uniform sampler2D u_Sampler;\n" +
        "varying vec2 v_TexCoord;\n" +
        "void main(){\n" +
        "   gl_FragColor = texture2D(u_Sampler, v_TexCoord);\n" +
        "}\n";

    //中间平面图形的高和宽
    var offset_width = 512;
    var offset_height = 512;

    function main() {
        var canvas = document.getElementById("canvas");

        var gl = getWebGLContext(canvas);

        if(!gl){
            console.log("无法获取WebGL的上下文");
            return;
        }

        //创建并初始化着色器
        if(!initShaders(gl, vertexShaderSource, fragmentShaderSource)){
            console.log("无法初始化着色器");
            return;
        }

        //得到attribute变量和uniform变量的存储位置
        var program = gl.program;//获取到程序对象
        program.a_Position = gl.getAttribLocation(program, "a_Position");
        program.a_TexCoord = gl.getAttribLocation(program, "a_TexCoord");
        program.u_MvpMatrix = gl.getUniformLocation(program, "u_MvpMatrix");
        if(program.a_Position < 0 || program.a_TexCoord < 0 || !program.u_MvpMatrix){
            console.log("无法获取到变量的存储位置");
            return;
        }

        //设置顶点的位置信息
        var cube = initVertexBuffersForCube(gl);
        var plane = initVertexBuffersForPlane(gl);

        if(!cube || !plane){
            console.log("存入缓冲区数据失败");
            return;
        }

        //设置纹理
        var texture = initTextures(gl);
        if(!texture){
            console.log("无法创建纹理缓冲区");
            return;
        }

        //初始化帧缓冲区
        var fbo = initFramebufferObject(gl);
        if(!fbo){
            console.log("无法初始化帧缓冲区");
            return;
        }

        //开启隐藏面消除功能
        gl.enable(gl.DEPTH_TEST);

        //设置视图投影矩阵相关信息
        var viewProjectMatrix = new Matrix4();
        viewProjectMatrix.setPerspective(30.0, canvas.width/canvas.height, 1.0, 100.0);
        viewProjectMatrix.lookAt(0.0, 3.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

        //设置帧缓冲区的视图投影矩阵
        var viewProjectMatrixFbo = new Matrix4();
        viewProjectMatrixFbo.setPerspective(30.0, offset_width/offset_height, 1.0, 100.0);
        viewProjectMatrixFbo.lookAt(0.0, -3.0, 5.0,0.0, 0.0, 0.0,0.0,1.0,0.0);

        //开始绘制
        var currentAngle = 0.0;
        function tick() {
            currentAngle = animate(currentAngle); //更新旋转角度
            draw(gl, canvas, fbo, plane, cube, currentAngle, texture, viewProjectMatrix, viewProjectMatrixFbo);
            requestAnimationFrame(tick);
        }

        tick();
    }

    function draw(gl, canvas, fbo, plane, cube, angle, texture, viewProjectMatrix, viewProjectMatrixFbo) {
        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo); //更改绘图的目标为帧缓冲区
        gl.viewport(0,0,offset_width, offset_height); //对帧缓冲区设置视口

        gl.clearColor(0.2,0.2,0.4,1.0); //设置背景色
        gl.clear(gl.COLOR_BUFFER_BIT |  gl.DEPTH_BUFFER_BIT); //清除背景和隐藏面消除

        //绘制立方体
        drawTexturedCube(gl, gl.program, cube, angle, texture, viewProjectMatrixFbo,false);

        gl.bindFramebuffer(gl.FRAMEBUFFER, null); //将绘制的目标修改为颜色缓冲区
        gl.viewport(0,0,canvas.width, canvas.height); //将视口的大小设置为canvas的大小

        gl.clearColor(0.0,0.0,0.0,1.0);
        gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT); //清除背景和隐藏面消除

        //绘制平面
        drawTexturedPlane(gl, gl.program, plane, 0.0, fbo.texture, viewProjectMatrix);

       
        
       
        drawTexturedCube(gl, gl.program, cube, angle, texture, viewProjectMatrix,true);
    }

    //声明坐标转换矩阵

    var g_mvpMatrix = new Matrix4();

    function drawTexturedPlane(gl, program, obj,  angle, texture, viewProjectMatrix) {
        var g_modelMatrix = new Matrix4();
        //计算模型矩阵
        // g_modelMatrix.setTranslate(0.0,0.0,1.0);
        //g_modelMatrix.setRotate(0.0,0.0,1.0,0.0);
        g_modelMatrix.rotate(angle, 0.0, 1.0, 0.0);
        //g_modelMatrix.translate(0.0,0.5,0.0)
        //计算模型视图投影矩阵，并赋值给u_MvpMatrix
        g_mvpMatrix.set(viewProjectMatrix);
        g_mvpMatrix.multiply(g_modelMatrix);
        gl.uniformMatrix4fv(program.u_MvpMatrix,  false, g_mvpMatrix.elements);

        drawTexturedObject(gl, program, obj, texture);
    }

    function drawTexturedCube(gl, program, obj, angle, texture, viewProjectMatrix,isTrans) {
        var g_modelMatrix = new Matrix4();
       
        //计算模型矩阵
        g_modelMatrix.setRotate(0.0,1.0,0.0,0.0);
        g_modelMatrix.rotate(angle, 0.0,1.0,0.0);
        g_modelMatrix.translate(0.0,1.0,0.0)
        g_modelMatrix.scale(0.5,0.5,0.5)
        if(!isTrans){
           
            
        }else{
            //g_modelMatrix.scale(0.5,0.5,0.5)
        }
        //计算模型视图投影矩阵，并赋值给u_mvpmatrix
        g_mvpMatrix.set(viewProjectMatrix);
        g_mvpMatrix.multiply(g_modelMatrix);
        gl.uniformMatrix4fv(program.u_MvpMatrix,false, g_mvpMatrix.elements);

        //绘制
        drawTexturedObject(gl, program, obj, texture);
    }

    function drawTexturedObject(gl, program, obj,  texture) {
        //分配缓冲区对象并启用赋值
        initAttributeVariable(gl, program.a_Position, obj.vertexBuffer); //顶点坐标
        initAttributeVariable(gl, program.a_TexCoord, obj.texCoordBuffer); //纹理坐标

        //将纹理对象绑定到目标
        gl.activeTexture(gl.TEXTURE0);
        gl.bindTexture(gl.TEXTURE_2D, texture);

        //绘制
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, obj.indexBuffer);
        gl.drawElements(gl.TRIANGLES, obj.numIndices, obj.indexBuffer.type, 0);
    }

    function initAttributeVariable(gl, a_attribute, buffer) {
        gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
        gl.vertexAttribPointer(a_attribute, buffer.num, buffer.type, false, 0, 0);
        gl.enableVertexAttribArray(a_attribute);
    }

    var angle_step = 30;
    var last = +new Date();
    function animate(angle) {
        var now = +new Date();
        var elapsed = now - last;
        last = now;
        var newAngle = angle + (angle_step*elapsed)/1000.0;
        return newAngle%360;
    }

    function initFramebufferObject(gl) {
        var framebuffer, texture, depthBuffer;

        //定义错误函数
        function error() {
            if(framebuffer) gl.deleteFramebuffer(framebuffer);
            if(texture) gl.deleteFramebuffer(texture);
            if(depthBuffer) gl.deleteFramebuffer(depthBuffer);
            return null;
        }

        //创建帧缓冲区对象
        framebuffer = gl.createFramebuffer();
        if(!framebuffer){
            console.log("无法创建帧缓冲区对象");
            return error();
        }

        //创建纹理对象并设置其尺寸和参数
        texture = gl.createTexture();
        if(!texture){
            console.log("无法创建纹理对象");
            return error();
        }

        gl.bindTexture(gl.TEXTURE_2D, texture);
        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, offset_width, offset_height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
        framebuffer.texture = texture;//将纹理对象存入framebuffer

        //创建渲染缓冲区对象并设置其尺寸和参数
        depthBuffer = gl.createRenderbuffer();
        if(!depthBuffer){
            console.log("无法创建渲染缓冲区对象");
            return error();
        }

        gl.bindRenderbuffer(gl.RENDERBUFFER, depthBuffer);
        gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, offset_width, offset_height);

        //将纹理和渲染缓冲区对象关联到帧缓冲区对象上
        gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
        gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
        gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER,depthBuffer);

        //检查帧缓冲区对象是否被正确设置
        var e = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
        if(gl.FRAMEBUFFER_COMPLETE !== e){
            console.log("渲染缓冲区设置错误"+e.toString());
            return error();
        }

        //取消当前的focus对象
        gl.bindFramebuffer(gl.FRAMEBUFFER, null);
        gl.bindTexture(gl.TEXTURE_2D, null);
        gl.bindRenderbuffer(gl.RENDERBUFFER, null);

        return framebuffer;
    }

    function initTextures(gl) {
        var texture = gl.createTexture();
        if(!texture){
            console.log("无法创建纹理缓冲区");
            return null;
        }

        var u_Sampler = gl.getUniformLocation(gl.program, "u_Sampler");
        if(!u_Sampler){
            console.log("无法获取到缓冲区对象");
            return null;
        }

        var img = new Image();

        img.onload = function () {
            gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, 1);
            gl.bindTexture(gl.TEXTURE_2D, texture);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
            gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, img);

            gl.uniform1i(u_Sampler, 0);

            gl.bindTexture(gl.TEXTURE_2D, null);
        };

        img.src = "/image/texture1.jpg";

        return texture;
    }

    function initVertexBuffersForPlane(gl) {
        // 创建一个面
        //  v1------v0
        //  |        |
        //  |        |
        //  |        |
        //  v2------v3

        // 顶点的坐标
        var vertices = new Float32Array([
            1.0, 0.0, 1.0,  -1.0, 0.0, 1.0,  -1.0,0.0, -1.0,   1.0,0.0, -1.0    // v0-v1-v2-v3
        ]);

        // 纹理的坐标
        var texCoords = new Float32Array([1.0, 1.0,   0.0, 1.0,   0.0, 0.0,   1.0, 0.0]);

        // 顶点的索引
        var indices = new Uint8Array([0, 1, 2,   0, 2, 3]);

        //将顶点的信息写入缓冲区对象
        var obj = {};
        obj.vertexBuffer = initArrayBufferForLaterUse(gl, vertices, 3, gl.FLOAT);
        obj.texCoordBuffer = initArrayBufferForLaterUse(gl, texCoords, 2, gl.FLOAT);
        obj.indexBuffer = initElementArrayBufferForLaterUse(gl, indices, gl.UNSIGNED_BYTE);
        if(!obj.vertexBuffer || !obj.texCoordBuffer || !obj.indexBuffer) return null;

        obj.numIndices = indices.length;

        gl.bindBuffer(gl.ARRAY_BUFFER, null);
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);

        return obj;
    }

    function initVertexBuffersForCube(gl) {
        // Create a cube
        //    v6----- v5
        //   /|      /|
        //  v1------v0|
        //  | |     | |
        //  | |v7---|-|v4
        //  |/      |/
        //  v2------v3

        // 顶点的数据坐标
        var vertices = new Float32Array([
            1.0, 1.0, 1.0,  -1.0, 1.0, 1.0,  -1.0,-1.0, 1.0,   1.0,-1.0, 1.0,    // v0-v1-v2-v3 front
            1.0, 1.0, 1.0,   1.0,-1.0, 1.0,   1.0,-1.0,-1.0,   1.0, 1.0,-1.0,    // v0-v3-v4-v5 right
            1.0, 1.0, 1.0,   1.0, 1.0,-1.0,  -1.0, 1.0,-1.0,  -1.0, 1.0, 1.0,    // v0-v5-v6-v1 up
            -1.0, 1.0, 1.0,  -1.0, 1.0,-1.0,  -1.0,-1.0,-1.0,  -1.0,-1.0, 1.0,    // v1-v6-v7-v2 left
            -1.0,-1.0,-1.0,   1.0,-1.0,-1.0,   1.0,-1.0, 1.0,  -1.0,-1.0, 1.0,    // v7-v4-v3-v2 down
            1.0,-1.0,-1.0,  -1.0,-1.0,-1.0,  -1.0, 1.0,-1.0,   1.0, 1.0,-1.0     // v4-v7-v6-v5 back
        ]);

        // 纹理的数据坐标
        var texCoords = new Float32Array([
            1.0, 1.0,   0.0, 1.0,   0.0, 0.0,   1.0, 0.0,    // v0-v1-v2-v3 front
            0.0, 1.0,   0.0, 0.0,   1.0, 0.0,   1.0, 1.0,    // v0-v3-v4-v5 right
            1.0, 0.0,   1.0, 1.0,   0.0, 1.0,   0.0, 0.0,    // v0-v5-v6-v1 up
            1.0, 1.0,   0.0, 1.0,   0.0, 0.0,   1.0, 0.0,    // v1-v6-v7-v2 left
            0.0, 0.0,   1.0, 0.0,   1.0, 1.0,   0.0, 1.0,    // v7-v4-v3-v2 down
            0.0, 0.0,   1.0, 0.0,   1.0, 1.0,   0.0, 1.0     // v4-v7-v6-v5 back
        ]);

        // 顶点的索引数据
        var indices = new Uint8Array([
            0, 1, 2,   0, 2, 3,    // front
            4, 5, 6,   4, 6, 7,    // right
            8, 9,10,   8,10,11,    // up
            12,13,14,  12,14,15,    // left
            16,17,18,  16,18,19,    // down
            20,21,22,  20,22,23     // back
        ]);

        //创建一个对象保存数据
        var obj = {};

        //将顶点信息写入缓冲区对象
        obj.vertexBuffer = initArrayBufferForLaterUse(gl, vertices, 3, gl.FLOAT);
        obj.texCoordBuffer = initArrayBufferForLaterUse(gl, texCoords, 2, gl.FLOAT);
        obj.indexBuffer = initElementArrayBufferForLaterUse(gl, indices, gl.UNSIGNED_BYTE);
        if(!obj.vertexBuffer || !obj.texCoordBuffer || !obj.indexBuffer) return null;

        obj.numIndices = indices.length;

        gl.bindBuffer(gl.ARRAY_BUFFER, null);
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);

        return obj;
    }

    function initArrayBufferForLaterUse(gl, data, num, type) {
        var buffer = gl.createBuffer();
        if(!buffer){
            console.log("无法创建缓冲区对象");
            return null;
        }

        gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
        gl.bufferData(gl.ARRAY_BUFFER, data, gl.STATIC_DRAW);

        buffer.num = num;
        buffer.type = type;

        return buffer;
    }

    function initElementArrayBufferForLaterUse(gl, data, type) {
        var buffer = gl.createBuffer();
        if(!buffer){
            console.log("无法创建着色器");
            return null;
        }

        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffer);
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, data, gl.STATIC_DRAW);

        buffer.type = type;

        return buffer;
    }
</script>
</html>

    效果：


    20211221_005011.gif

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