index.html
<html>
<head>
<meta lang="en">
<meta charset="UTF-8">
<title>webgl 簡單動畫</title>
<script src="../lib/cuon-utils.js"></script>
<script src="../lib/cuon-matrix.js"></script>
<style>
body{
margin:0;
}
canvas{
display:block;
border:1px solid #999;
}
.btn-group {
width: 500px;
text-align: center;
padding: 10px 0;
}
</style>
</head>
<body>
<canvas id="canvas" width="500" height="500"></canvas>
</body>
<script src="./index.js"></script>
index.js
// 頂點著色器程序
var VSHADER_SOURCE =`
attribute vec4 a_Position;
uniform mat4 m_matrix4;
void main() {
//設(shè)置坐標
gl_Position = m_matrix4 * a_Position;
//設(shè)置尺寸
gl_PointSize = 10.0;
}
`;
// 片元著色器
var FSHADER_SOURCE =`
precision mediump float;
uniform vec4 u_FragColor;
void main() {
//設(shè)置顏色
gl_FragColor = vec4(0.5, 0.2, 0.5, 0.5);
}
`;
// 獲取canvas元素
var canvas = document.getElementById('canvas');
// 獲取繪制二維上下文
var gl = canvas.getContext('webgl');
gl.clearColor(0, 0, 0, 1);
// 初始化shader
initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE);
// 初始化頂點
var n = initVertexBuffer(gl);
var matrix = new Matrix4(); // 變換舉證
function draw(gl, n, angle, matrix) {
gl.clear(gl.COLOR_BUFFER_BIT);
var m_matrix4 = gl.getUniformLocation(gl.program, 'm_matrix4');
matrix.rotate(angle, 0, 0, 1);
gl.uniformMatrix4fv(m_matrix4, false, matrix.elements);
gl.drawArrays(gl.TRIANGLES, 0, n );
}
/**
* 初始化頂點
*/
function initVertexBuffer(gl) {
var unit = 0.25;
var l = Math.sqrt(3);
var vertices = new Float32Array([
0, 2,
-l, -1,
l, -1
]);
vertices.forEach((v,idx, arr)=> arr[idx] = v * unit);
var size = 2;
var pointCount = vertices.byteLength / size / Float32Array.BYTES_PER_ELEMENT;
// 創(chuàng)建緩沖區(qū)
var vertexBuffer = gl.createBuffer();
// 將緩沖區(qū)綁定到目標
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
// 向緩沖區(qū)寫入數(shù)據(jù)
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
// 將緩沖區(qū)對象分配給a_Position
gl.vertexAttribPointer(a_Position, size, gl.FLOAT, false, 0, 0);
// 激活attibue 是緩沖區(qū)對attribute變量分配生效
gl.enableVertexAttribArray(a_Position);
return pointCount;
}
var prev;
function tick(timestamp) {
!prev && (prev = timestamp);
var period = timestamp - prev;
var angle = period * 90 / 1000; // 每秒90度
draw(gl, n, angle, matrix);
prev = timestamp;
requestAnimationFrame(tick);
}
requestAnimationFrame(tick);
以下函數(shù)庫詳見 http://www.reibang.com/p/589579ee70b2
<script src="../lib/cuon-utils.js"></script>
<script src="../lib/cuon-matrix.js"></script>
image.png
