WebGL笔记：WebGL中JS与GLSL ES 语言通信，着色器间的数据传输示例：用鼠标控制点位

用鼠标控制点位

<canvas id="canvas"></canvas><!-- 顶点着色器 -->
<script id="vertexShader" type="x-shader/x-vertex">attribute vec4 a_Position;void main() {// 点位gl_Position = a_Position;// 尺寸gl_PointSize = 50.0;}
</script><!-- 片元着色器 -->
<script id="fragmentShader" type="x-shader/x-fragment">void main() {gl_FragColor = vec4(1,1,0,1);}</script><script type="module">import { initShaders } from "./utils.js";const canvas = document.querySelector("#canvas");canvas.width = window.innerWidth;canvas.height = window.innerHeight;// 获取着色器文本const vsSource = document.querySelector("#vertexShader").innerText;const fsSource = document.querySelector("#fragmentShader").innerText;// 三维画笔const gl = canvas.getContext("webgl");// 初始化着色器initShaders(gl, vsSource, fsSource);// 设置attribute 变量const a_Position = gl.getAttribLocation(gl.program, "a_Position");gl.vertexAttrib1f(a_Position, 0.1);// 声明颜色 rgbagl.clearColor(0, 0, 0, 1);// 刷底色gl.clear(gl.COLOR_BUFFER_BIT);// 绘制顶点gl.drawArrays(gl.POINTS, 0, 1);// 鼠标点击事件canvas.addEventListener("click", ({ clientX, clientY }) => {const { left, top, width, height } = canvas.getBoundingClientRect();const [cssX, cssY] = [clientX - left, clientY - top];//解决坐标原点位置的差异const [halfWidth, halfHeight] = [width / 2, height / 2];const [xBaseCenter, yBaseCenter] = [cssX - halfWidth,cssY - halfHeight,];// 解决y 方向的差异const yBaseCenterTop = -yBaseCenter;// 解决坐标基底的差异const [x, y] = [xBaseCenter / halfWidth, yBaseCenterTop / halfHeight];gl.vertexAttrib2f(a_Position, x, y);// gl.clear(gl.COLOR_BUFFER_BIT);gl.drawArrays(gl.POINTS, 0, 1);});
</script>

utils.js

export function initShaders(gl, vsSource, fsSource) {// 创建程序对象const program = gl.createProgram();// 建立着色对象const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);// 把顶点着色对象装进程序对象中gl.attachShader(program, vertexShader);// 把片元着色对象装进程序对象中gl.attachShader(program, fragmentShader);// 连接webgl上下文对象和程序对象gl.linkProgram(program);// 启动程序对象gl.useProgram(program);// 将程序对象挂到上下文对象上gl.program = program;return true;
}function loadShader(gl, type, source) {// 根据着色类型，建立着色器对象const shader = gl.createShader(type);// 将着色器源文件传入着色器对象中gl.shaderSource(shader, source);// 编译着色器对象gl.compileShader(shader);// 返回着色器对象return shader;
}

这里核心点主要在: canvas坐标系和webgl坐标系之间的差异，由此计算出鼠标在webgl坐标系中的位置，并且控制点的位置

两者坐标系的核心算法

const { left, top, width, height } = canvas.getBoundingClientRect();
const [cssX, cssY] = [clientX - left, clientY - top];//解决坐标原点位置的差异
const [halfWidth, halfHeight] = [width / 2, height / 2];
const [xBaseCenter, yBaseCenter] = [cssX - halfWidth,cssY - halfHeight
];
// 解决y 方向的差异
const yBaseCenterTop = -yBaseCenter;
// 解决坐标基底的差异
const [x, y] = [xBaseCenter / halfWidth, yBaseCenterTop / halfHeight];