webgl-矩阵、旋转、平移、缩放

news2025/1/18 11:54:50

关键代码

旋转

/*

* [

* cosB, -sinB, 0, 0,

* sinB, cosB, 0, 0,

* 0, 0, 1, 0,

* 0, 0, 0, 1

* ]

*

* 矩阵本该是这个但是由于webgl的矩阵行和列是颠倒的所以我们传入的矩阵也需要倒置

*/

rotationMatrix = [

cosB, sinB, 0, 0,

-sinB, cosB, 0, 0,

0, 0, 1, 0,

0, 0, 0, 1

]

平移矩阵

//向x轴正方向平移0.2

translateMatrix = [

1, 0, 0, 0.2,

0, 1, 0, 0,

0, 0, 1, 0,

0, 0, 0, 1

]

缩放矩阵

//沿着x,y轴放大2倍

scaleMatrix =[

2, 0, 0, 0,

0, 2, 0, 0,

0, 0, 1, 0,

0, 0, 0, 1

]

html

<!DOCTYPE html>

<head>

<style>

*{

margin: 0px;

padding: 0px;

}

</style>

</head>

<body>

<canvas id = 'webgl'>

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</canvas>

<script src="./main.js"></script>

</body>

main.js

let canvas = document.getElementById('webgl')

canvas.width = window.innerWidth

canvas.height = window.innerHeight

let radio = window.innerWidth / window.innerHeight;

let ctx = canvas.getContext('webgl')

//创建顶点资源和像素资源（颜色）

let vertexSource = `

attribute vec2 a_position;

uniform mat4 matrix;

void main() {

gl_Position = matrix * vec4(a_position, 0.0, 1.0);

gl_PointSize = 10.0;

}

`

let fragmentSource = `

precision mediump float;

void main (){

gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);

}

`

if (initShader(ctx, vertexSource, fragmentSource)) {

//画三角形

let vertexs = [

// x y R G B

-0.5, 0.0, 1.0, 0.0, 0.0, //第一个点的信息

0.5, 0.0, 0.0, 1.0, 0.0, //第二个点的信息

0.0, 0.5, 0.0, 0.0, 1.0,//第三个点的信息

]

let float32Array = new Float32Array(vertexs)

//创建buffer

let buffer = ctx.createBuffer()

//绑定buffer

ctx.bindBuffer(ctx.ARRAY_BUFFER, buffer)

//往buffer中填充值，并指定数据用途

ctx.bufferData(ctx.ARRAY_BUFFER, float32Array, ctx.STATIC_DRAW)

//获取vertexShader指定变量内存

let a_Position = ctx.getAttribLocation(ctx.program, "a_position")

//指定每两个数组元素为一个点

/*

* 当数组元素不需进行分割拆分的时候最后两位可以指定为0，0

*

*

*/

ctx.vertexAttribPointer(

a_Position, //location: vertex Shader里面的attributes变量的location

2, ctx.FLOAT, //size: attribute变量的长度 vec2长度2 vec3长度3

false, //normalized: 正交化 true或false , [1, 2] => [1/根号5， 2/根号5]

5 * float32Array.BYTES_PER_ELEMENT, //stride: 每个点的信息所占的BYTES

0 //offset: 每个点的信息，从第几个BYTES开始数

)

ctx.enableVertexAttribArray(a_Position);

// ctx.drawArrays(ctx.TRIANGLE_FAN, 0, 3)

//旋转矩阵

let angle = 0

let rotationMatrix

let translateMatrix

function render() {

angle++

let cosB = Math.cos(angle / 180 * Math.PI)

let sinB = Math.sin(angle / 180 * Math.PI)

/*

* [

* cosB, -sinB, 0, 0,

* sinB, cosB, 0, 0,

* 0, 0, 1, 0,

* 0, 0, 0, 1

* ]

*

* 矩阵本该是这个但是由于webgl的矩阵行和列是颠倒的所以我们传入的矩阵也需要倒置

*/

rotationMatrix = [

cosB, sinB, 0, 0,

-sinB, cosB, 0, 0,

0, 0, 1, 0,

0, 0, 0, 1

]

//向x轴正方向平移0.2

translateMatrix = [

1, 0, 0, 0.2,

0, 1, 0, 0,

0, 0, 1, 0,

0, 0, 0, 1

]

//沿着x,y轴放大2倍

scaleMatrix =[

2, 0, 0, 0,

0, 2, 0, 0,

0, 0, 1, 0,

0, 0, 0, 1

]

let matrix = ctx.getUniformLocation(ctx.program, "matrix")

ctx.uniformMatrix4fv(

matrix, //localtion:vertex Shader里面的attributes变量的location

false, //是否转置一定设置为false

new Float32Array(rotationMatrix)

)

ctx.drawArrays(ctx.TRIANGLE_FAN, 0, 3)

window.requestAnimationFrame(render)

}

render()

}

//创建顶点阴影和像素阴影

function createShader(ctx, type, source) {

//创建shader

let shader = ctx.createShader(type)

//绑定

ctx.shaderSource(shader, source)

//编译shader

ctx.compileShader(shader)

//获取编译结果

let compiler = ctx.getShaderParameter(shader, ctx.COMPILE_STATUS)

if (compiler) {

return shader

} else {

let log = ctx.getShaderInfoLog(shader)

console.log("compile shaders error", log)

//删除异常的shader,防止内存泄露

ctx.deleteShader(shader)

return null

}

}

function createProgram(ctx, vertexShader, fragmentShader) {

//创建program

let program = ctx.createProgram()

if (!program) {

return null

}

//点资源和像素资源合并

ctx.attachShader(program, vertexShader)

ctx.attachShader(program, fragmentShader)

ctx.linkProgram(program)

//获取linked的结果

let linked = ctx.getProgramParameter(program, ctx.LINK_STATUS)

if (linked) {

return program

} else {

//获取link错误信息

let log = ctx.getProgramInfoLog(program)

console.log("link program error", log)

//删除防止内存泄漏

ctx.delete(program)

ctx.deleteShader(vertexShader)

ctx.deleteShader(fragmentShader)

return null

}

}

function initShader(ctx, vertexSource, fragmentSource) {

let vertexShader = createShader(ctx, ctx.VERTEX_SHADER, vertexSource)

let fragmentShader = createShader(ctx, ctx.FRAGMENT_SHADER, fragmentSource)

let program = createProgram(ctx, vertexShader, fragmentShader)

if (program) {

ctx.useProgram(program)

//挂载到ctx

ctx.program = program

return true

} else {

return false

}

}