前言

WebGL（全写Web Graphics Library）是一种3D绘图协议，这种绘图技术标准允许把JavaScript和OpenGL ES 2.0结合在一起，通过增加OpenGL ES 2.0的一个JavaScript绑定，WebGL可以为HTML5 Canvas提供硬件3D加速渲染，这样Web开发人员就可以借助系统显卡来在浏览器里更流畅地展示3D场景和模型了，还能创建复杂的导航和数据视觉化。显然，WebGL技术标准免去了开发网页专用渲染插件的麻烦，可被用于创建具有复杂3D结构的网站页面，甚至可以用来设计3D网页游戏等等。–百度百科

在现实中webgl的用途很多，比如医院运维网站，地铁运维网站，海绵城市，可以以三维网页形式展示出现实状态。

WebGL相关文档：http://doc.yonyoucloud.com/doc/wiki/project/webgl/webgL-fundamentals.html

在这里插入图片描述

一、webgl的使用

安装第三方包：npm i --save threejs-miniprogram

1.立体图形的绘制

import drawCube from './drawCube'Page({/*** 页面的初始数据*/data: {},/*** 生命周期函数--监听页面加载*/onLoad: function (options) {},/*** 生命周期函数--监听页面初次渲染完成*/onReady: function () {wx.createSelectorQuery().select('#myCanvas1').node().exec((res) => {const canvas = res[0].nodeconst gl = canvas.getContext('webgl')if (!gl) {console.log('webgl未受支持');return}// 检查所有支持的扩展var available_extensions = gl.getSupportedExtensions();console.log(available_extensions);// 清除画布// 使用完全不透明的黑色清除所有图像，我们将清除色设为黑色，此时并没有开始清除gl.clearColor(0.0, 0.0, 0.0, 1.0);// 用上面指定的颜色清除缓冲区gl.clear(gl.COLOR_BUFFER_BIT);// 画的是一个正方形drawCube(gl, canvas)
})

import {mat4
} from '../../lib/gl-matrix'var cubeRotation = 0.0;//
// Start here
//
function drawCube(gl,canvas) {// Vertex shader programconst vsSource = `attribute vec4 aVertexPosition;attribute vec4 aVertexColor;uniform mat4 uModelViewMatrix;uniform mat4 uProjectionMatrix;varying lowp vec4 vColor;void main(void) {gl_Position = uProjectionMatrix * uModelViewMatrix * aVertexPosition;vColor = aVertexColor;}`;// Fragment shader programconst fsSource = `varying lowp vec4 vColor;void main(void) {gl_FragColor = vColor;}`;// Initialize a shader program; this is where all the lighting// for the vertices and so forth is established.const shaderProgram = initShaderProgram(gl, vsSource, fsSource);// Collect all the info needed to use the shader program.// Look up which attributes our shader program is using// for aVertexPosition, aVevrtexColor and also// look up uniform locations.const programInfo = {program: shaderProgram,attribLocations: {vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),vertexColor: gl.getAttribLocation(shaderProgram, 'aVertexColor'),},uniformLocations: {projectionMatrix: gl.getUniformLocation(shaderProgram, 'uProjectionMatrix'),modelViewMatrix: gl.getUniformLocation(shaderProgram, 'uModelViewMatrix'),},};// Here's where we call the routine that builds all the// objects we'll be drawing.const buffers = initBuffers(gl);var then = 0;// Draw the scene repeatedlyfunction render(now) {now *= 0.001;  // convert to secondsconst deltaTime = now - then;then = now;drawScene(gl, programInfo, buffers, deltaTime);canvas.requestAnimationFrame(render);}canvas.requestAnimationFrame(render);
}//
// initBuffers
//
// Initialize the buffers we'll need. For this demo, we just
// have one object -- a simple three-dimensional cube.
//
function initBuffers(gl) {// Create a buffer for the cube's vertex positions.const positionBuffer = gl.createBuffer();// Select the positionBuffer as the one to apply buffer// operations to from here out.gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);// Now create an array of positions for the cube.const positions = [// Front face-1.0, -1.0,  1.0,1.0, -1.0,  1.0,1.0,  1.0,  1.0,-1.0,  1.0,  1.0,// Back face-1.0, -1.0, -1.0,-1.0,  1.0, -1.0,1.0,  1.0, -1.0,1.0, -1.0, -1.0,// Top face-1.0,  1.0, -1.0,-1.0,  1.0,  1.0,1.0,  1.0,  1.0,1.0,  1.0, -1.0,// Bottom face-1.0, -1.0, -1.0,1.0, -1.0, -1.0,1.0, -1.0,  1.0,-1.0, -1.0,  1.0,// Right face1.0, -1.0, -1.0,1.0,  1.0, -1.0,1.0,  1.0,  1.0,1.0, -1.0,  1.0,// Left face-1.0, -1.0, -1.0,-1.0, -1.0,  1.0,-1.0,  1.0,  1.0,-1.0,  1.0, -1.0,];// Now pass the list of positions into WebGL to build the// shape. We do this by creating a Float32Array from the// JavaScript array, then use it to fill the current buffer.gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);// Now set up the colors for the faces. We'll use solid colors// for each face.const faceColors = [[1.0,  1.0,  1.0,  1.0],    // Front face: white[1.0,  0.0,  0.0,  1.0],    // Back face: red[0.0,  1.0,  0.0,  1.0],    // Top face: green[0.0,  0.0,  1.0,  1.0],    // Bottom face: blue[1.0,  1.0,  0.0,  1.0],    // Right face: yellow[1.0,  0.0,  1.0,  1.0],    // Left face: purple];// Convert the array of colors into a table for all the vertices.var colors = [];for (var j = 0; j < faceColors.length; ++j) {const c = faceColors[j];// Repeat each color four times for the four vertices of the facecolors = colors.concat(c, c, c, c);// colors = colors.concat(c);// colors = colors.concat(c);// colors = colors.concat(c);// colors = colors.concat(c);}const colorBuffer = gl.createBuffer();gl.bindBuffer(gl.ARRAY_BUFFER, colorBuffer);gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);// Build the element array buffer; this specifies the indices// into the vertex arrays for each face's vertices.const indexBuffer = gl.createBuffer();gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);// This array defines each face as two triangles, using the// indices into the vertex array to specify each triangle's// position.const indices = [0,  1,  2,      0,  2,  3,    // front4,  5,  6,      4,  6,  7,    // back8,  9,  10,     8,  10, 11,   // top12, 13, 14,     12, 14, 15,   // bottom16, 17, 18,     16, 18, 19,   // right20, 21, 22,     20, 22, 23,   // left];// Now send the element array to GLgl.bufferData(gl.ELEMENT_ARRAY_BUFFER,new Uint16Array(indices), gl.STATIC_DRAW);return {position: positionBuffer,color: colorBuffer,indices: indexBuffer,};
}//
// Draw the scene.
//
function drawScene(gl, programInfo, buffers, deltaTime) {gl.clearColor(0.0, 0.0, 0.0, 1.0);  // Clear to black, fully opaquegl.clearDepth(1.0);                 // Clear everythinggl.enable(gl.DEPTH_TEST);           // Enable depth testinggl.depthFunc(gl.LEQUAL);            // Near things obscure far things// Clear the canvas before we start drawing on it.gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);// Create a perspective matrix, a special matrix that is// used to simulate the distortion of perspective in a camera.// Our field of view is 45 degrees, with a width/height// ratio that matches the display size of the canvas// and we only want to see objects between 0.1 units// and 100 units away from the camera.const fieldOfView = 45 * Math.PI / 180;   // in radiansconst aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;const zNear = 0.1;const zFar = 100.0;const projectionMatrix = mat4.create();// note: glmatrix.js always has the first argument// as the destination to receive the result.mat4.perspective(projectionMatrix,fieldOfView,aspect,zNear,zFar);// Set the drawing position to the "identity" point, which is// the center of the scene.const modelViewMatrix = mat4.create();// Now move the drawing position a bit to where we want to// start drawing the square.mat4.translate(modelViewMatrix,     // destination matrixmodelViewMatrix,     // matrix to translate[-0.0, 0.0, -6.0]);  // amount to translatemat4.rotate(modelViewMatrix,  // destination matrixmodelViewMatrix,  // matrix to rotatecubeRotation,     // amount to rotate in radians[0, 0, 1]);       // axis to rotate around (Z)mat4.rotate(modelViewMatrix,  // destination matrixmodelViewMatrix,  // matrix to rotatecubeRotation * .7,// amount to rotate in radians[0, 1, 0]);       // axis to rotate around (Y)// Tell WebGL how to pull out the positions from the position// buffer into the vertexPosition attribute{const numComponents = 3;const type = gl.FLOAT;const normalize = false;const stride = 0;const offset = 0;gl.bindBuffer(gl.ARRAY_BUFFER, buffers.position);gl.vertexAttribPointer(programInfo.attribLocations.vertexPosition,numComponents,type,normalize,stride,offset);gl.enableVertexAttribArray(programInfo.attribLocations.vertexPosition);}// Tell WebGL how to pull out the colors from the color buffer// into the vertexColor attribute.{const numComponents = 4;const type = gl.FLOAT;const normalize = false;const stride = 0;const offset = 0;gl.bindBuffer(gl.ARRAY_BUFFER, buffers.color);gl.vertexAttribPointer(programInfo.attribLocations.vertexColor,numComponents,type,normalize,stride,offset);gl.enableVertexAttribArray(programInfo.attribLocations.vertexColor);}// gl.ARRAY_BUFFER: 包含顶点属性的Buffer，如顶点坐标，纹理坐标数据或顶点颜色数据。
// gl.ELEMENT_ARRAY_BUFFER: 用于元素索引的Buffer。// Tell WebGL which indices to use to index the verticesgl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffers.indices);// Tell WebGL to use our program when drawinggl.useProgram(programInfo.program);// Set the shader uniformsgl.uniformMatrix4fv(programInfo.uniformLocations.projectionMatrix,false,projectionMatrix);gl.uniformMatrix4fv(programInfo.uniformLocations.modelViewMatrix,false,modelViewMatrix);{// 6个面，12个三角形，每个三角3个顶点，共36个顶点const vertexCount = 36;const type = gl.UNSIGNED_SHORT;const offset = 0;gl.drawElements(gl.TRIANGLES, vertexCount, type, offset);}// Update the rotation for the next drawcubeRotation += deltaTime;
}//
// Initialize a shader program, so WebGL knows how to draw our data
//
function initShaderProgram(gl, vsSource, fsSource) {const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);// Create the shader programconst shaderProgram = gl.createProgram();gl.attachShader(shaderProgram, vertexShader);gl.attachShader(shaderProgram, fragmentShader);gl.linkProgram(shaderProgram);// If creating the shader program failed, alertif (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {alert('Unable to initialize the shader program: ' + gl.getProgramInfoLog(shaderProgram));return null;}return shaderProgram;
}//
// creates a shader of the given type, uploads the source and
// compiles it.
//
function loadShader(gl, type, source) {const shader = gl.createShader(type);// Send the source to the shader objectgl.shaderSource(shader, source);// Compile the shader programgl.compileShader(shader);// See if it compiled successfullyif (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {alert('An error occurred compiling the shaders: ' + gl.getShaderInfoLog(shader));gl.deleteShader(shader);return null;}return shader;
}export default drawCube