WebGL简易教程(十一)：纹理

基于《WebGL简易教程(九)：综合实例：地形的绘制》中的JS代码进行改进：

// 顶点着色器程序507383170 var VSHADER_SOURCE = ‘attribute vec4 a_Position;\n‘ + //位置 ‘attribute vec4 a_Color;\n‘ + //颜色 ‘uniform mat4 u_MvpMatrix;\n‘ + ‘varying vec4 v_Color;\n‘ + ‘varying vec4 v_position;\n‘ + ‘void main() {\n‘ + ‘ v_position = a_Position;\n‘ + ‘ gl_Position = u_MvpMatrix * a_Position;\n‘ + // 设置顶点坐标 ‘ v_Color = a_Color;\n‘ + ‘}\n‘; // 片元着色器程序 var FSHADER_SOURCE = ‘precision mediump float;\n‘ + ‘uniform vec2 u_RangeX;\n‘ + //X方向范围 ‘uniform vec2 u_RangeY;\n‘ + //Y方向范围 ‘uniform sampler2D u_Sampler;\n‘ + ‘varying vec4 v_Color;\n‘ + ‘varying vec4 v_position;\n‘ + ‘void main() {\n‘ + ‘ vec2 v_TexCoord = vec2((v_position.x-u_RangeX[0]) / (u_RangeX[1]-u_RangeX[0]), 1.0-(v_position.y-u_RangeY[0]) / (u_RangeY[1]-u_RangeY[0]));\n‘ + ‘ gl_FragColor = texture2D(u_Sampler, v_TexCoord);\n‘ + ‘}\n‘; //定义一个矩形体：混合构造函数原型模式 function Cuboid(minX, maxX, minY, maxY, minZ, maxZ) { this.minX = minX; this.maxX = maxX; this.minY = minY; this.maxY = maxY; this.minZ = minZ; this.maxZ = maxZ; } Cuboid.prototype = { constructor: Cuboid, CenterX: function () { return (this.minX + this.maxX) / 2.0; }, CenterY: function () { return (this.minY + this.maxY) / 2.0; }, CenterZ: function () { return (this.minZ + this.maxZ) / 2.0; }, LengthX: function () { return (this.maxX - this.minX); }, LengthY: function () { return (this.maxY - this.minY); } } //定义DEM function Terrain() { } Terrain.prototype = { constructor: Terrain, setWH: function (col, row) { this.col = col; this.row = row; } } var currentAngle = [0.0, 0.0]; // 绕X轴Y轴的旋转角度 ([x-axis, y-axis]) var curScale = 1.0; //当前的缩放比例 var initTexSuccess = false; //纹理图像是否加载完成 function main() { var demFile = document.getElementById(‘demFile‘); if (!demFile) { console.log("Failed to get demFile element!"); return; } //加载文件后的事件 demFile.addEventListener("change", function (event) { //判断浏览器是否支持FileReader接口 if (typeof FileReader == ‘undefined‘) { console.log("你的浏览器不支持FileReader接口！"); return; } //读取文件后的事件 var reader = new FileReader(); reader.onload = function () { if (reader.result) { var terrain = new Terrain(); if (!readDEMFile(reader.result, terrain)) { console.log("文件格式有误，不能读取该文件！"); } //绘制函数 onDraw(gl, canvas, terrain); } } var input = event.target; reader.readAsText(input.files[0]); }); // 获取 <canvas> 元素 var canvas = document.getElementById(‘webgl‘); // 获取WebGL渲染上下文 var gl = getWebGLContext(canvas); if (!gl) { console.log(‘Failed to get the rendering context for WebGL‘); return; } // 初始化着色器 if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) { console.log(‘Failed to intialize shaders.‘); return; } // 指定清空<canvas>的颜色 gl.clearColor(0.0, 0.0, 0.0, 1.0); // 开启深度测试 gl.enable(gl.DEPTH_TEST); //清空颜色和深度缓冲区 gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT); } //绘制函数 function onDraw(gl, canvas, terrain) { // 设置顶点位置 //var cuboid = new Cuboid(399589.072, 400469.072, 3995118.062, 3997558.062, 732, 1268); var n = initVertexBuffers(gl, terrain); if (n < 0) { console.log(‘Failed to set the positions of the vertices‘); return; } //设置纹理 if (!initTextures(gl, terrain)) { console.log(‘Failed to intialize the texture.‘); return; } //注册鼠标事件 initEventHandlers(canvas); //绘制函数 var tick = function () { if (initTexSuccess) { //设置MVP矩阵 setMVPMatrix(gl, canvas, terrain.cuboid); //清空颜色和深度缓冲区 gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT); //绘制矩形体 gl.drawElements(gl.TRIANGLES, n, gl.UNSIGNED_SHORT, 0); //gl.drawArrays(gl.Points, 0, n); } //请求浏览器调用tick requestAnimationFrame(tick); }; //开始绘制 tick(); } function initTextures(gl, terrain) { // 传递X方向和Y方向上的范围到着色器 var u_RangeX = gl.getUniformLocation(gl.program, ‘u_RangeX‘); var u_RangeY = gl.getUniformLocation(gl.program, ‘u_RangeY‘); if (!u_RangeX || !u_RangeY) { console.log(‘Failed to get the storage location of u_RangeX or u_RangeY‘); return; } gl.uniform2f(u_RangeX, terrain.cuboid.minX, terrain.cuboid.maxX); gl.uniform2f(u_RangeY, terrain.cuboid.minY, terrain.cuboid.maxY); //创建一个image对象 var image = new Image(); if (!image) { console.log(‘Failed to create the image object‘); return false; } //图像加载的响应函数 image.onload = function () { if (loadTexture(gl, image)) { initTexSuccess = true; } }; //浏览器开始加载图像 image.src = ‘tex.jpg‘; return true; } function loadTexture(gl, image) { // 创建纹理对象 var texture = gl.createTexture(); if (!texture) { console.log(‘Failed to create the texture object‘); return false; } // 开启0号纹理单元 gl.activeTexture(gl.TEXTURE0); // 绑定纹理对象 gl.bindTexture(gl.TEXTURE_2D, texture); // 设置纹理参数 gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR); gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR); gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE); gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE); // 配置纹理图像 gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, gl.RGB, gl.UNSIGNED_BYTE, image); // 将0号单元纹理传递给着色器中的取样器变量 var u_Sampler = gl.getUniformLocation(gl.program, ‘u_Sampler‘); if (!u_Sampler) { console.log(‘Failed to get the storage location of u_Sampler‘); return false; } gl.uniform1i(u_Sampler, 0); return true; } //读取DEM函数 function readDEMFile(result, terrain) { var stringlines = result.split("\n"); if (!stringlines || stringlines.length <= 0) { return false; } //读取头信息 var subline = stringlines[0].split("\t"); if (subline.length != 6) { return false; } var col = parseInt(subline[4]); //DEM宽 var row = parseInt(subline[5]); //DEM高 var verticeNum = col * row; if (verticeNum + 1 > stringlines.length) { return false; } terrain.setWH(col, row); //读取点信息 var ci = 0; terrain.verticesColors = new Float32Array(verticeNum * 6); for (var i = 1; i < stringlines.length; i++) { if (!stringlines[i]) { continue; } var subline = stringlines[i].split(‘,‘); if (subline.length != 9) { continue; } for (var j = 0; j < 6; j++) { terrain.verticesColors[ci] = parseFloat(subline[j]); ci++; } } if (ci !== verticeNum * 6) { return false; } //包围盒 var minX = terrain.verticesColors[0]; var maxX = terrain.verticesColors[0]; var minY = terrain.verticesColors[1]; var maxY = terrain.verticesColors[1]; var minZ = terrain.verticesColors[2]; var maxZ = terrain.verticesColors[2]; for (var i = 0; i < verticeNum; i++) { minX = Math.min(minX, terrain.verticesColors[i * 6]); maxX = Math.max(maxX, terrain.verticesColors[i * 6]); minY = Math.min(minY, terrain.verticesColors[i * 6 + 1]); maxY = Math.max(maxY, terrain.verticesColors[i * 6 + 1]); minZ = Math.min(minZ, terrain.verticesColors[i * 6 + 2]); maxZ = Math.max(maxZ, terrain.verticesColors[i * 6 + 2]); } terrain.cuboid = new Cuboid(minX, maxX, minY, maxY, minZ, maxZ); return true; } //注册鼠标事件 function initEventHandlers(canvas) { var dragging = false; // Dragging or not var lastX = -1, lastY = -1; // Last position of the mouse //鼠标按下 canvas.onmousedown = function (ev) { var x = ev.clientX; var y = ev.clientY; // Start dragging if a moue is in <canvas> var rect = ev.target.getBoundingClientRect(); if (rect.left <= x && x < rect.right && rect.top <= y && y < rect.bottom) { lastX = x; lastY = y; dragging = true; } }; //鼠标离开时 canvas.onmouseleave = function (ev) { dragging = false; }; //鼠标释放 canvas.onmouseup = function (ev) { dragging = false; }; //鼠标移动 canvas.onmousemove = function (ev) { var x = ev.clientX; var y = ev.clientY; if (dragging) { var factor = 100 / canvas.height; // The rotation ratio var dx = factor * (x - lastX); var dy = factor * (y - lastY); currentAngle[0] = currentAngle[0] + dy; currentAngle[1] = currentAngle[1] + dx; } lastX = x, lastY = y; }; //鼠标缩放 canvas.onmousewheel = function (event) { if (event.wheelDelta > 0) { curScale = curScale * 1.1; } else { curScale = curScale * 0.9; } }; } //设置MVP矩阵 function setMVPMatrix(gl, canvas, cuboid) { // Get the storage location of u_MvpMatrix var u_MvpMatrix = gl.getUniformLocation(gl.program, ‘u_MvpMatrix‘); if (!u_MvpMatrix) { console.log(‘Failed to get the storage location of u_MvpMatrix‘); return; } //模型矩阵 var modelMatrix = new Matrix4(); modelMatrix.scale(curScale, curScale, curScale); modelMatrix.rotate(currentAngle[0], 1.0, 0.0, 0.0); // Rotation around x-axis modelMatrix.rotate(currentAngle[1], 0.0, 1.0, 0.0); // Rotation around y-axis modelMatrix.translate(-cuboid.CenterX(), -cuboid.CenterY(), -cuboid.CenterZ()); //投影矩阵 var fovy = 60; var near = 1; var projMatrix = new Matrix4(); projMatrix.setPerspective(fovy, canvas.width / canvas.height, 1, 10000); //计算lookAt()函数初始视点的高度 var angle = fovy / 2 * Math.PI / 180.0; var eyeHight = (cuboid.LengthY() * 1.2) / 2.0 / angle; //视图矩阵 var viewMatrix = new Matrix4(); // View matrix viewMatrix.lookAt(0, 0, eyeHight, 0, 0, 0, 0, 1, 0); //MVP矩阵 var mvpMatrix = new Matrix4(); mvpMatrix.set(projMatrix).multiply(viewMatrix).multiply(modelMatrix); //将MVP矩阵传输到着色器的uniform变量u_MvpMatrix gl.uniformMatrix4fv(u_MvpMatrix, false, mvpMatrix.elements); } // function initVertexBuffers(gl, terrain) { //DEM的一个网格是由两个三角形组成的 // 0------1 1 // | | // | | // col col------col+1 var col = terrain.col; var row = terrain.row; var indices = new Uint16Array((row - 1) * (col - 1) * 6); var ci = 0; for (var yi = 0; yi < row - 1; yi++) { //for (var yi = 0; yi < 10; yi++) { for (var xi = 0; xi < col - 1; xi++) { indices[ci * 6] = yi * col + xi; indices[ci * 6 + 1] = (yi + 1) * col + xi; indices[ci * 6 + 2] = yi * col + xi + 1; indices[ci * 6 + 3] = (yi + 1) * col + xi; indices[ci * 6 + 4] = (yi + 1) * col + xi + 1; indices[ci * 6 + 5] = yi * col + xi + 1; ci++; } } // var verticesColors = terrain.verticesColors; var FSIZE = verticesColors.BYTES_PER_ELEMENT; //数组中每个元素的字节数 // 创建缓冲区对象 var vertexColorBuffer = gl.createBuffer(); var indexBuffer = gl.createBuffer(); if (!vertexColorBuffer || !indexBuffer) { console.log(‘Failed to create the buffer object‘); return -1; } // 将缓冲区对象绑定到目标 gl.bindBuffer(gl.ARRAY_BUFFER, vertexColorBuffer); // 向缓冲区对象写入数据 gl.bufferData(gl.ARRAY_BUFFER, verticesColors, gl.STATIC_DRAW); //获取着色器中attribute变量a_Position的地址 var a_Position = gl.getAttribLocation(gl.program, ‘a_Position‘); if (a_Position < 0) { console.log(‘Failed to get the storage location of a_Position‘); return -1; } // 将缓冲区对象分配给a_Position变量 gl.vertexAttribPointer(a_Position, 3, gl.FLOAT, false, FSIZE * 6, 0); // 连接a_Position变量与分配给它的缓冲区对象 gl.enableVertexAttribArray(a_Position); //获取着色器中attribute变量a_Color的地址 var a_Color = gl.getAttribLocation(gl.program, ‘a_Color‘); if (a_Color < 0) { console.log(‘Failed to get the storage location of a_Color‘); return -1; } // 将缓冲区对象分配给a_Color变量 gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, FSIZE * 6, FSIZE * 3); // 连接a_Color变量与分配给它的缓冲区对象 gl.enableVertexAttribArray(a_Color); // 将顶点索引写入到缓冲区对象 gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer); gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW); return indices.length; }

主要作了以下三点的改动以使用纹理。