# 2. 示例

// 顶点着色器程序
'attribute vec4 a_Position;\n' + // attribute variable
'attribute vec4 a_Color;\n' +
'uniform mat4 u_MvpMatrix;\n' +
'varying vec4 v_Color;\n' +
'void main() {\n' +
'  gl_Position = u_MvpMatrix * a_Position;\n' + // Set the vertex coordinates of the point
'  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);
}
}

var currentAngle = [35.0, 30.0]; // 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() {
// 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;
}

// 设置顶点位置
var cuboid = new Cuboid(399589.072, 400469.072, 3995118.062, 3997558.062, 732, 1268);
var n = initVertexBuffers(gl, cuboid);
if (n < 0) {
console.log('Failed to set the positions of the vertices');
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);

//绘制函数
var tick = function () {
//设置MVP矩阵
setMVPMatrix(gl, canvas, 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_BYTE, 0);

//请求浏览器调用tick
requestAnimationFrame(tick);
};

//开始绘制
tick();

// 绘制矩形体
gl.drawElements(gl.TRIANGLES, n, gl.UNSIGNED_BYTE, 0);
}

//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, cuboid) {
// Create a cube
//    v6----- v5
//   /|      /|
//  v1------v0|
//  | |     | |
//  | |v7---|-|v4
//  |/      |/
//  v2------v3
// 顶点坐标和颜色
var verticesColors = new Float32Array([
cuboid.maxX, cuboid.maxY, cuboid.maxZ, 1.0, 1.0, 1.0,  // v0 White
cuboid.minX, cuboid.maxY, cuboid.maxZ, 1.0, 0.0, 1.0,  // v1 Magenta
cuboid.minX, cuboid.minY, cuboid.maxZ, 1.0, 0.0, 0.0,  // v2 Red
cuboid.maxX, cuboid.minY, cuboid.maxZ, 1.0, 1.0, 0.0,  // v3 Yellow
cuboid.maxX, cuboid.minY, cuboid.minZ, 0.0, 1.0, 0.0,  // v4 Green
cuboid.maxX, cuboid.maxY, cuboid.minZ, 0.0, 1.0, 1.0,  // v5 Cyan
cuboid.minX, cuboid.maxY, cuboid.minZ, 0.0, 0.0, 1.0,  // v6 Blue
cuboid.minX, cuboid.minY, cuboid.minZ, 1.0, 0.0, 1.0   // v7 Black
]);

//顶点索引
var indices = new Uint8Array([
0, 1, 2, 0, 2, 3,    // 前
0, 3, 4, 0, 4, 5,    // 右
0, 5, 6, 0, 6, 1,    // 上
1, 6, 7, 1, 7, 2,    // 左
7, 4, 3, 7, 3, 2,    // 下
4, 7, 6, 4, 6, 5     // 后
]);

//
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;
}

## 2.1. 顶点索引绘制

//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);
}
}

//...

// 顶点坐标和颜色
var verticesColors = new Float32Array([
cuboid.maxX, cuboid.maxY, cuboid.maxZ, 1.0, 1.0, 1.0,  // v0 White
cuboid.minX, cuboid.maxY, cuboid.maxZ, 1.0, 0.0, 1.0,  // v1 Magenta
cuboid.minX, cuboid.minY, cuboid.maxZ, 1.0, 0.0, 0.0,  // v2 Red
cuboid.maxX, cuboid.minY, cuboid.maxZ, 1.0, 1.0, 0.0,  // v3 Yellow
cuboid.maxX, cuboid.minY, cuboid.minZ, 0.0, 1.0, 0.0,  // v4 Green
cuboid.maxX, cuboid.maxY, cuboid.minZ, 0.0, 1.0, 1.0,  // v5 Cyan
cuboid.minX, cuboid.maxY, cuboid.minZ, 0.0, 0.0, 1.0,  // v6 Blue
cuboid.minX, cuboid.minY, cuboid.minZ, 1.0, 0.0, 1.0   // v7 Black
]);

//...


//顶点索引
var indices = new Uint8Array([
0, 1, 2, 0, 2, 3,    // 前
0, 3, 4, 0, 4, 5,    // 右
0, 5, 6, 0, 6, 1,    // 上
1, 6, 7, 1, 7, 2,    // 左
7, 4, 3, 7, 3, 2,    // 下
4, 7, 6, 4, 6, 5     // 后
]);

// 创建缓冲区对象
var indexBuffer = gl.createBuffer();

//...

// 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);

// 绘制矩形体
gl.drawElements(gl.TRIANGLES, n, gl.UNSIGNED_BYTE, 0);

## 2.2. MVP矩阵设置

MVP矩阵的设置同样放置在setMVPMatrix()函数中。

### 2.2.1. 模型矩阵

var currentAngle = [35.0, 30.0]; // 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

//...

//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());

### 2.2.2. 投影矩阵

//投影矩阵
var fovy = 60;
var near = 1;
var projMatrix = new Matrix4();
projMatrix.setPerspective(fovy, canvas.width / canvas.height, 1, 10000);

### 2.2.3. 视图矩阵

//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);

### 2.2.4. MVP矩阵

//MVP矩阵
var mvpMatrix = new Matrix4();
mvpMatrix.set(projMatrix).multiply(viewMatrix).multiply(modelMatrix);

# 4. 参考

posted @ 2019-10-06 21:09  charlee44  阅读(...)  评论(... 编辑 收藏