08.缩放
2020-03-20 本文已影响0人
cmd_ts
clipboard.png
顶点着色器需要加上 uniform mat4 u_xformMatrix, 存储缩放因子的坐标矢量。
顶点坐标位置 ： gl_Position = u_xformMatrix * a_Position
缩放API ： gl.uniformMatrix4fv(u_xformMatrix, false, xformMatrix);
u_xformMatrix ： 缩放因子
xformMatrix ： 原始坐标
<script type="shader" id="vertex">
attribute vec4 a_Position;
uniform mat4 u_xformMatrix;
void main(){
gl_PointSize = 2.0;
gl_Position = a_Position * u_xformMatrix;
}
</script>
var Sx = 2, Sy = 2, Sz = 1.0;
var xformMatrix = new Float32Array([
Sx, 0.0, 0.0, 0.0,
0.0, Sy, 0.0, 0.0,
0.0, 0.0, Sz, 0.0,
0.0, 0.0, 0.0, 1.0
]);
gl.uniformMatrix4fv(u_xformMatrix, false, xformMatrix);
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>cmd_webgl_study3</title>
</head>
<body>
<!-- 1.创建webgl标签 -->
<canvas id="webgl" width="500" height="500"></canvas>
<script type="shader" id="vertex">
attribute vec4 a_Position;
uniform mat4 u_xformMatrix;
void main(){
gl_PointSize = 2.0;
gl_Position = a_Position * u_xformMatrix;
}
</script>
<script type="shader" id="fragment">
precision mediump float;
uniform vec4 vColor;
void main(){
gl_FragColor = vec4(0.0,1.0,0.0,1.0);
}
</script>
<script src="./libs/webgl_libs.js"></script>
<script>
// 2.得到canvas element
let canvas = document.getElementById('webgl');
// 3.得到上下文对象 context
let gl = canvas.getContext('webgl');
//4.编写顶点着色器源代码、实际绘制的代码，GPU：描述一个顶点的大小、位置（3d坐标） 顶点着色器
let vertex_shader_source = document.getElementById("vertex").innerHTML;
//5.片元着色器源代码：描述一个点的颜色 片元着色器
let fragment_shader_source = document.getElementById("fragment").innerHTML;
let program = create_program(gl,vertex_shader_source,fragment_shader_source);
//获取坐标点
let apos = gl.getAttribLocation(program,'a_Position');
let u_xformMatrix = gl.getUniformLocation(program, 'u_xformMatrix');
var test = new Float32Array([
.5,.3,
.8,.3
]);
console.log('test:',test);
let asd = test*2;
console.log('asd:',asd);
var Sx = 2, Sy = 2, Sz = 1.0;
var xformMatrix = new Float32Array([
Sx, 0.0, 0.0, 0.0,
0.0, Sy, 0.0, 0.0,
0.0, 0.0, Sz, 0.0,
0.0, 0.0, 0.0, 1.0
]);
gl.uniformMatrix4fv(u_xformMatrix, false, xformMatrix);
// 1.创建buf
let buffer = gl.createBuffer();
//2.绑定buf
gl.bindBuffer(gl.ARRAY_BUFFER,buffer);
//3.
let data = new Float32Array([
0.0,0.5,
-0.5,0.0,
0.5,0.0
]);
//向缓冲区写入数据
gl.bufferData(gl.ARRAY_BUFFER,data,gl.STATIC_DRAW);
//将缓冲区对象分配给a_Position变量
gl.vertexAttribPointer(apos,2,gl.FLOAT,false,0,0);
gl.enableVertexAttribArray(apos);
// 13.设置背景色
gl.clearColor(1.0,0.0,0.0,1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
// 14.绘制
gl.drawArrays(gl.TRIANGLES,0,3);
</script>
</body>
</html>
