WebGL 3D（varying内插）
2018-12-17 本文已影响35人
WebGiser
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<!DOCTYPE HTML>
<head>
</head>
<html>
<body onload="main()">
<canvas id="webgl" width="500" height="500" style="border: 1px solid #ff0000;">
</canvas>
<script type="text/javascript">
//顶点着色器程序
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n'+
'attribute vec4 a_Color;\n'+
'varying vec4 v_Color;\n'+ //varying变量
'void main(){\n'+
'gl_Position = a_Position;\n'+
'gl_PointSize = 10.0;\n'+
'v_Color = a_Color;\n'+ //将数据传给片元着色器
'}\n';
//片元着色器程序
var FSHADER_SOURCE =
'precision mediump float;\n'+
'varying vec4 v_Color;\n'+
'void main(){\n'+
'gl_FragColor = v_Color;\n'+ //从顶点着色器接收数据
'}\n';
function main(){
//获取<canvas>元素
var canvas = document.getElementById("webgl");
if(!canvas){
console.log('error');
return;
}
//获取绘制三维图形的绘图上下文
var gl = canvas.getContext('webgl');
// 创建着色器对象
const fShader = gl.createShader(gl.FRAGMENT_SHADER);
const vShader = gl.createShader(gl.VERTEX_SHADER);
// 将着色器源码写入对象
gl.shaderSource(vShader, VSHADER_SOURCE);
gl.shaderSource(fShader, FSHADER_SOURCE);
// 编译着色器
gl.compileShader(vShader);
gl.compileShader(fShader);
// 创建程序
const program = gl.createProgram();
// 程序绑定着色器
gl.attachShader(program, vShader);
gl.attachShader(program, fShader);
// 链接程序
gl.linkProgram(program);
// 使用程序
gl.useProgram(program);
var n = initVertexBuffers(gl);
if(n < 0){
console.log('Failed to set positions of vertices');
return;
}
gl.drawArrays(gl.TRIANGLES, 0, n);
function initVertexBuffers(gl){
var verticesColors = new Float32Array([
//顶点坐标和颜色
0.0, 0.5, 1.0, 0.0, 0.0,
-0.5, -0.5, 0.0, 1.0, 0.0,
0.5, -0.5, 0.0, 0.0, 1.0
]);
var n = 3; //顶点个数
//创建缓冲区对象
var vertexColorBuffer = gl.createBuffer();
if(!vertexColorBuffer){
console.log('Failed to create the buffer object');
return;
}
//将缓冲区对象绑定到目标
gl.bindBuffer(gl.ARRAY_BUFFER, vertexColorBuffer);
//向缓冲区对象中写入数据
gl.bufferData(gl.ARRAY_BUFFER, verticesColors, gl.STATIC_DRAW);
//verticesColors数组中每个元素所占的字节数
var FSIZE = verticesColors.BYTES_PER_ELEMENT;
//获取a_Position的存储位置
var a_Position = gl.getAttribLocation(program, 'a_Position');
if(a_Position < 0){
console.log('Failed to get the storage location of a_Position');
return;
}
//将缓冲区对象分配给a_Position变量
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, FSIZE * 5, 0);
//连接a_Position变量与分配给它的缓冲区对象
gl.enableVertexAttribArray(a_Position);
//获取a_Color的存储位置
var a_Color = gl.getAttribLocation(program, 'a_Color');
if(a_Color < 0){
console.log('Failed to get the storage location of a_Color');
return;
}
//将缓冲区对象分配给a_Color变量
gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, FSIZE * 5, FSIZE * 2);
//连接a_Position变量与分配给它的缓冲区对象
gl.enableVertexAttribArray(a_Color);
return n;
}
}
</script>
</body>
</html>
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