08 WebGL通过点击绘制点

来源：互联网发布：西装软件编辑：程序博客网时间：2024/06/04 19:20
<!doctype html><html><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>Document</title></head><body onload="main()"><canvas id="canvas" height="400" width="400">    你的浏览器不支持WebGL，请更换新的浏览器</canvas></body><script src="lib/webgl-utils.js" ></script><script src="lib/webgl-debug.js" ></script><script src="lib/cuon-utils.js" ></script><script>    //顶点着色器程序    var VSHADER_SOURCE="" +        "attribute vec4 a_Position;\n" +        "void main(){\n" +        "   gl_Position = a_Position;\n" +//设置坐标        "   gl_PointSize = 5.0;\n" +//设置尺寸        "}\n";    //片元着色器程序    var FSHADER_SOURCE = "" +        "void main(){\n" +        "   gl_FragColor = vec4(1.0,0.0,0.0,1.0);\n" +//设置颜色        "}\n";    function main() {        //首先获取到canvas的dom对象        var canvas = document.getElementById("canvas");        //获取到WebGL的上下文        var gl = getWebGLContext(canvas);        //不支持WebGL的浏览器将打印一个错误，并结束代码运行        if (!gl) {            console.log("浏览器不支持WebGL");            return;        }        //初始化着色器        if(!initShaders(gl,VSHADER_SOURCE,FSHADER_SOURCE)){            console.log("初始化着色器失败");            return;        }        //获取attribute变量的存储位置        var a_Position = gl.getAttribLocation(gl.program, "a_Position");        if(a_Position < 0){            console.log("无法获取变量的存储位置");            return;        }        //指定一个覆盖（清空）canvas的颜色        gl.clearColor(0.0, 0.0, 0.0, 1.0);        //清除canvas        gl.clear(gl.COLOR_BUFFER_BIT);        //注册鼠标点击事件        canvas.onmousedown = function (event) {            click(event,gl,canvas,a_Position);        }        var g_poiont = [];//声明一个可以存储点的信息的数组        function click(event,gl,canvas,a_Position) {            var e = event || window.event;            var x = e.clientX;//获取鼠标的点距离浏览器窗口最左边的距离            var y = e.clientY;//获取鼠标的点距离浏览器窗口最上面的距离            var rect = e.target.getBoundingClientRect();//组件封装方法，返回对象，里面含有点击的标签的距离浏览器左侧、上侧、右侧、下侧和自身的高宽            x = ((x-rect.left) - canvas.height/2)/(canvas.height/2);//计算出x轴WebGL的浮点数            y = (canvas.width/2 - (y - rect.top))/(canvas.width/2);//计算出y轴WebGL的浮点数            g_poiont.push({x:x,y:y});//将数据存入数组            //清除canvas            gl.clear(gl.COLOR_BUFFER_BIT);            var len = g_poiont.length;            for(var i = 0; i<len; i++){//循环添加点                //将点的位置传递到变量中a_position                gl.vertexAttrib3f(a_Position,g_poiont[i].x,g_poiont[i].y,0.0);                //绘制点                gl.drawArrays(gl.POINTS,0,1);            }        }    }</script></html>
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