想要把三维物体显示到网页上面，很简单，只要会css，懂得盒子模型，定位，就可以在网页上面随意放置模型，控制canvas位置就可以。
这次的案例直接body添加了一个背景，然后看到的效果就是这样的，一个立方体在网页上面旋转。
实现这个效果也只是将背景修改成了全透明，也就是将gl.clearColor()方法里面传入的第四个值改为0.0 。就达到了效果。
<!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;
background: url("lib/banner.jpg");
background-size: cover;
}
#canvas{
margin: 0;
display: block;
position: absolute;
}
#canvas{
z-index: 0;
}
</style>
</head>
<body οnlοad="main()">
<canvas id="canvas" height="800" width="1200"></canvas>
</body>
<script src="webgl/webgl-utils.js"></script>
<script src="webgl/webgl-debug.js"></script>
<script src="webgl/cuon-utils.js"></script>
<script src="webgl/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;
//顶点着色器
var vertexShaderSource = "" +
"attribute vec4 a_Position;\n" +
"attribute vec4 a_Color;\n" +
"attribute float a_Face;\n" +//表面编号，不是用int类型
"uniform mat4 u_MvpMatrix;\n" +
"uniform int u_PickedFace;\n" + //被选中的表面编号
"varying vec4 v_Color;\n" +
"void main (){\n" +
" gl_Position = u_MvpMatrix * a_Position;\n" +
" int face = int(a_Face);\n" +
" vec3 color = (face == u_PickedFace) ? vec3(1.0) : a_Color.rgb;\n" +
" if(u_PickedFace == 0){\n" +
" v_Color = vec4(color, a_Face/255.0);\n" +
" }else{\n" +
" v_Color = vec4(color, a_Color.a);\n" +
" }\n" +
"}\n";
//片元着色器
var fragmentShaderSource = "" +
"#ifdef GL_ES\n" +
"precision mediump float;\n" +
"#endif\n" +
"varying vec4 v_Color;\n" +
"void main(){\n" +
" gl_FragColor = v_Color;\n" +
"}\n";
function main() {
//获取WebGL对象
var gl = getWebGLContext(canvas);
//初始化着色器
initShaders(gl, vertexShaderSource, fragmentShaderSource);
//将数据存入缓冲区
var n = initVertexBuffers(gl);
if (n < 0) {
console.log("数据存入缓冲区失败");
return;
}
//设置背景色和开启层级关系
gl.clearColor(0.0, 0.0, 0.0, 0.0);
gl.enable(gl.DEPTH_TEST);
//获取uniform变量的存储位置
var u_MvpMatrix = gl.getUniformLocation(gl.program, "u_MvpMatrix");
var u_PickedFace = gl.getUniformLocation(gl.program, "u_PickedFace");
if (!u_MvpMatrix || !u_PickedFace) {
console.log("无法获取相关的存储位置");
return;
}
//设置视点和投影矩阵
var viewProjectionMatrix = new Matrix4();
viewProjectionMatrix.setPerspective(30.0, canvas.width / canvas.height, 1.0, 100.0);
viewProjectionMatrix.lookAt(0.0, 0.0, 7.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
//设置一个自动转圈的变量
var currentAngle = 0.0;
// 初始化被选中的表面的变量
gl.uniform1i(u_PickedFace, -1);
//定时绘制页面
var tick = function () {
currentAngle = animate(currentAngle);
draw(gl, n, currentAngle, viewProjectionMatrix, u_MvpMatrix);
requestAnimationFrame(tick);
};
tick();
}
//修改currentAngle的值
var last = +new Date();
var angleStep = 20.0;//每次旋转的速度
function animate(currentAngle) {
var now = +new Date();
var elapsed = now - last;
last = now;
//这里是为了保证旋转保证匀速旋转
var newAngle = currentAngle + (angleStep * elapsed) / 1000;
return newAngle % 360;
}
//设置顶点数据和将数据存入缓冲区
function initVertexBuffers(gl) {
// Create a cube
// v6----- v5
// /| /|
// v1------v0|
// | | | |
// | |v7---|-|v4
// |/ |/
// v2------v3
var vertices = new Float32Array([ // Vertex coordinates 顶点的位置数据
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
]);
var colors = new Float32Array([ // Colors 顶点的颜色数据
0.32, 0.18, 0.56, 0.32, 0.18, 0.56, 0.32, 0.18, 0.56, 0.32, 0.18, 0.56, // v0-v1-v2-v3 front
0.5, 0.41, 0.69, 0.5, 0.41, 0.69, 0.5, 0.41, 0.69, 0.5, 0.41, 0.69, // v0-v3-v4-v5 right
0.78, 0.69, 0.84, 0.78, 0.69, 0.84, 0.78, 0.69, 0.84, 0.78, 0.69, 0.84, // v0-v5-v6-v1 up
0.0, 0.32, 0.61, 0.0, 0.32, 0.61, 0.0, 0.32, 0.61, 0.0, 0.32, 0.61, // v1-v6-v7-v2 left
0.27, 0.58, 0.82, 0.27, 0.58, 0.82, 0.27, 0.58, 0.82, 0.27, 0.58, 0.82, // v7-v4-v3-v2 down
0.73, 0.82, 0.93, 0.73, 0.82, 0.93, 0.73, 0.82, 0.93, 0.73, 0.82, 0.93 // v4-v7-v6-v5 back
]);
var faces = new Uint8Array([ // Faces 顶点的面的数据
1, 1, 1, 1, // v0-v1-v2-v3 front
2, 2, 2, 2, // v0-v3-v4-v5 right
3, 3, 3, 3, // v0-v5-v6-v1 up
4, 4, 4, 4, // v1-v6-v7-v2 left
5, 5, 5, 5, // v7-v4-v3-v2 down
6, 6, 6, 6 // v4-v7-v6-v5 back
]);
var indices = new Uint8Array([ // Indices of the vertices 顶点的索引数据
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
]);
//存入缓冲区
if (!initArrayBuffer(gl, vertices, gl.FLOAT, 3, "a_Position")) {
return -1;
}
if (!initArrayBuffer(gl, colors, gl.FLOAT, 3, "a_Color")) {
return -1;
}
if (!initArrayBuffer(gl, faces, gl.UNSIGNED_BYTE, 1, "a_Face")) {
return -1;
}
//创建索引缓冲区
var indexBuffer = gl.createBuffer();
if (indexBuffer < 0) {
console.log("无法创建缓冲区");
return -1;
}
//取消ARRAY_BUFFER中的绑定
gl.bindBuffer(gl.ARRAY_BUFFER, null);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);
return indices.length;
}
function initArrayBuffer(gl, data, type, num, attribute) {
var buffer = gl.createBuffer();
if (!buffer) {
console.log("无法创建缓冲区对象");
return;
}
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, data, gl.STATIC_DRAW);
var a_attribute = gl.getAttribLocation(gl.program, attribute);
if (a_attribute < 0) {
console.log("无法获取变量的存储位置" + attribute);
return false;
}
gl.vertexAttribPointer(a_attribute, num, type, false, 0, 0);
gl.enableVertexAttribArray(a_attribute);
return true;
}
//绘制
var matrix = new Matrix4();
function draw(gl, n, currentAngle, viewProjectionMatrix, u_MvpMatrix) {
matrix.set(viewProjectionMatrix);
matrix.rotate(currentAngle, 1.0, 0.0, 0.0);
matrix.rotate(currentAngle, 0.0, 1.0, 0.0);
matrix.rotate(currentAngle, 0.0, 0.0, 1.0);
gl.uniformMatrix4fv(u_MvpMatrix, false, matrix.elements);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
gl.drawElements(gl.TRIANGLES, n, gl.UNSIGNED_BYTE, 0);
}
</script>
</html>
