1 html
<html lang="en">
<head>
<title></title>
<meta charset="UTF-8">
<script type="text/javascript" src="../WebGL_Guide_Code/WebGL_Guide_Code/lib/cuon-utils.js"></script>
<script type="text/javascript" src="../WebGL_Guide_Code/WebGL_Guide_Code/lib/webgl-debug.js"></script>
<script type="text/javascript" src="../WebGL_Guide_Code/WebGL_Guide_Code/lib/webgl-utils.js"></script>
<style>
</style>
</head>
<body onload="main()">
<canvas id="canvas" width="400" height="400">
</canvas>
<script type="text/javascript" src="../WebGL_Guide_Code/WebGL_Guide_Code/lib/cuon-utils.js"></script>
<script type="text/javascript" src="../WebGL_Guide_Code/WebGL_Guide_Code/lib/webgl-debug.js"></script>
<script type="text/javascript" src="../WebGL_Guide_Code/WebGL_Guide_Code/lib/webgl-utils.js"></script>
<script type="text/javascript" src="drowPoint.js"></script>
</body>
</html>
2 js
// HelloPint2.js (c) 2012 matsuda
// Vertex shader program
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n' + // attribute variable
'void main() {\n' +
' gl_Position = a_Position;\n' +
' gl_PointSize = 10.0;\n' +
'}\n';
// Fragment shader program
var FSHADER_SOURCE =
'void main() {\n' +
' gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +
'}\n';
function main() {
// Retrieve <canvas> element
var canvas = document.getElementById('canvas');
// Get the rendering context for WebGL
var gl = getWebGLContext(canvas);
if (!gl) {
console.log('Failed to get the rendering context for WebGL');
return;
}
gl.clearColor(0.0, 0.0, 0.0, 1.0);
// Initialize shaders
if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) {
console.log('Failed to intialize shaders.');
return;
}
// Get the storage location of a_Position
var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
var a_PointSize = gl.getAttribLocation(gl.program, 'a_PointSize');
if (a_Position < 0) {
console.log('Failed to get the storage location of a_Position');
return;
}
canvas.onmousedown = function (ev) {
click(ev, gl, canvas, a_Position);
}
// Pass vertex position to attribute variable
}
var g_Points = []; // 鼠标点击的位置数组
function click (ev, gl, canvas, a_Position) {
var x = ev.clientX;
var y = ev.clientY;
var rect = ev.target.getBoundingClientRect();
x = ((x - rect.left) - canvas.height/2) / (canvas.height/2);
y = (canvas.width/2 - (y - rect.top)) / (canvas.width/2);
g_Points.push(x);
g_Points.push(y);
gl.clear(gl.COLOR_BUFFER_BIT);
var len = g_Points.length;
for (var i = 0; i < len; i += 2) {
gl.vertexAttrib3f(a_Position, g_Points[i], g_Points[i + 1], 0.0);
gl.drawArrays(gl.POINTS, 0, 1);
}
}
我们创建了两个着色器,相比1,我们给position的坐标是动态输入的在
'attribute vec4 a_Position;\n'
这行代码里,我们添加了一个attribute类型的对象,里面存放的是几个位置坐标,
var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
比较重要的是这里的a_Position存放的是第二个参数的地址,没有值!
gl.vertexAttrib3f(a_Position, g_Points[i], g_Points[i + 1], 0.0);
这里将a_Position变量为值传到上面的attribute对象里面,而后面我们传入的是动态的地址。后面的值用
var x = ev.clientX;
var y = ev.clientY;
var rect = ev.target.getBoundingClientRect();
x = ((x - rect.left) - canvas.height/2) / (canvas.height/2);
y = (canvas.width/2 - (y - rect.top)) / (canvas.width/2);
g_Points.push(x);
g_Points.push(y);
传入。
今天就到这里啦,一起加油!