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webgl-画三角形

article 2024/9/16 21:12:31

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 ctx = canvas.getContext('webgl')

//创建顶点资源和像素资源（颜色）

let vertexSource = `

attribute vec2 a_Position;

void main() {

gl_Position = vec4(a_Position, 0.0, 1.0);

gl_PointSize = 10.0;

}

`

let fragmentSource = `

precision mediump float;

uniform vec3 u_color;

void main (){

gl_FragColor = vec4(u_color, 1.0);

}

`

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

//设置颜色

let color = ctx.getUniformLocation(ctx.program, "u_color2")

ctx.uniform3f(color, 1.0, 0.0, 0.0)

//画三角形

let vertexs = [

-0.5, 0.0,

0.5, 0.0,

0.0, 0.5

]

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")

ctx.vertexAttribPointer(a_Position, 2, ctx.FLOAT, false, 0, 0)

//确认吧带有数据的buffer赋值给a_Position

ctx.enableVertexAttribArray(a_Position);

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

}

//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

}

}