# 2. 实例

## 2.1. TerrainViewer.html

<!DOCTYPE html>
<html>

<meta charset="utf-8" />
<title> 显示地形 </title>
<title>Hello Triangle</title>

<div><input type='file' id='demFile'></div>
<div>
<canvas id="webgl" width="600" height="600">
请使用支持WebGL的浏览器
</canvas>
</div>

<script src="../lib/webgl-utils.js"></script>
<script src="../lib/webgl-debug.js"></script>
<script src="../lib/cuon-utils.js"></script>
<script src="../lib/cuon-matrix.js"></script>
<script src="TerrainViewer.js"></script>
</body>

</html>


## 2.2. TerrainViewer.js

// 顶点着色器程序
'attribute vec4 a_Position;\n' +  //位置
'attribute vec4 a_Color;\n' + //颜色
'uniform mat4 u_MvpMatrix;\n' +
'varying vec4 v_Color;\n' +
'void main() {\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
'precision mediump float;\n' +
'varying vec4 v_Color;\n' +
'void main() {\n' +
'  gl_FragColor = v_Color;\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

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
if (typeof FileReader == 'undefined') {
return;
}

//读取文件后的事件
var terrain = new 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;
});

// 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
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;
}

//注册鼠标事件
initEventHandlers(canvas);

//绘制函数
var tick = function () {
//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();
}

//读取DEM函数
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;
}


//...

var demFile = document.getElementById('demFile');
if (!demFile) {
console.log("Failed to get demFile element!");
return;
}

//加载文件后的事件
if (typeof FileReader == 'undefined') {
return;
}

//读取文件后的事件
var terrain = new 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;
});

//...


//定义DEM
function Terrain() {
}
Terrain.prototype = {
constructor: Terrain,
setWH: function (col, row) {
this.col = col;
this.row = row;
}
}

//...

//读取DEM函数
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;
}


//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;
}

//注册鼠标事件
initEventHandlers(canvas);

//绘制函数
var tick = function () {
//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 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

//...

return indices.length;
}


# 4. 参考

posted @ 2019-10-08 19:13  charlee44  阅读(2563)  评论(2编辑  收藏  举报