# 2.实现要点

## 2.1绘制各个模型块

<子节点模型变换> = <父节点的模型变换> x <自身模型变换>

``````//声明模型变换矩阵和模型视图投影矩阵
var g_modelMatrix = new Matrix4()
var g_mvpMatrix = new Matrix4()

//绘制图形
function draw(gl, n, viewProjMatrix, u_MvpMatrix, u_NormalMatrix, u_VerticesColor) {

gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
gl.uniform3f(u_VerticesColor, 1.0, 0.4, 0.0)

//绘制基座
var baseHeight = 2.0 //基座的高度
g_modelMatrix.setTranslate(0.0, -12.0, 0.0) //设置为平移矩阵，并沿y轴向下移动12
drawBox(gl, n, 10.0, baseHeight, 10.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//方块
var cubeHeight = 2.0 //方块厚度
g_modelMatrix.setTranslate(0.0, -12.0, -16)
drawBox(gl, n, 10.0, cubeHeight, 10.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//第一节胳膊
var arm1Length = 10.0 //第一节胳膊的长度
g_modelMatrix.translate(0.0, baseHeight, 0.0)
g_modelMatrix.rotate(g_body_angle, 0.0, 1.0, 0.0)
drawBox(gl, n, 3.0, arm1Length, 3.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//第二节胳膊
var arm2Length = 16.0
g_modelMatrix.translate(0.0, arm1Length, 0.0) //移至arm1
g_modelMatrix.rotate(g_arm_angle, 0.0, 0.0, 1.0)
drawBox(gl, n, 4.0, arm2Length, 4.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//第三节胳膊
var arm3Length = 10.0
g_modelMatrix.translate(0.0, arm2Length, 0.0) //移至arm2
g_modelMatrix.rotate(g_arm_angle, 0.0, 0.0, 1.0)
drawBox(gl, n, 3.0, arm3Length, 3.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//手掌
var palmLength = 2.0
var handleLength = 8.0
g_modelMatrix.translate(0.0, handleLength, 0.0) //移至arm3
g_modelMatrix.rotate(0.0, 0.0, 1.0, 0.0)
drawBox(gl, n, 6.0, palmLength, 6.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//随手臂移动的方块
if (g_isHandleCube) {
gl.uniform3f(u_VerticesColor, 1.0, 0.0, 0.0)
var cubeHeight = 2.0 //方块厚度
g_modelMatrix.translate(0.0, cubeHeight, 0.0)
drawBox(gl, n, 10.0, cubeHeight, 10.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)
} else if (!g_isHandleCube && g_moveEnd) {
g_modelMatrix.setTranslate(0.0, -12.0, -32)
gl.uniform3f(u_VerticesColor, 1.0, 0.4, 0.0)
var cubeHeight = 2.0 //方块厚度
drawBox(gl, n, 10.0, cubeHeight, 10.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)
}

}
``````

## 2.2绘制方块函数

``````var g_matrixStack = [] //存储矩阵的数组
function pushMatrix(m) { //将矩阵压入栈
var m2 = new Matrix4(m)
g_matrixStack.push(m2)
}

function popMatrix() { //从栈中弹出矩阵
return g_matrixStack.pop()
}

var g_normalMatrix = new Matrix4() //变换法向量矩阵

//绘制立方体
function drawBox(gl, n, width, height, depth, viewProjMatrix, u_MvpMatrix, u_NormalMatrix) {
pushMatrix(g_modelMatrix) //备份变换前模型矩阵

g_modelMatrix.scale(width, height, depth)
//计算、设置模型视图投影矩阵
g_mvpMatrix.set(viewProjMatrix)
g_mvpMatrix.multiply(g_modelMatrix)
gl.uniformMatrix4fv(u_MvpMatrix, false, g_mvpMatrix.elements)

//计算、设置变换法向量矩阵
g_normalMatrix.setInverseOf(g_modelMatrix)
g_normalMatrix.transpose()
gl.uniformMatrix4fv(u_NormalMatrix, false, g_normalMatrix.elements)

//绘制
gl.drawElements(gl.TRIANGLES, n, gl.UNSIGNED_BYTE, 0)
g_modelMatrix = popMatrix() //将备份的模型矩阵赋值给全局模型矩阵
}

``````

## 2.3动画函数

``````//声明全局变量
var arm_step_angle = 1.0 //手臂每一次动画弯曲的角度
var body_step_angle = 3.0 //手臂整体每一次动画旋转角度
var g_body_angle = -90.0 //手臂整体的旋转角度
var g_arm_angle = -45.0 //手臂弯曲的角度
var g_isHandleCube = false
var g_moveEnd = false

var g_times = 0

function animate(gl, n, viewProjMatrix, u_MvpMatrix, u_NormalMatrix, u_VerticesColor) {
g_times++
if (g_times > 170) { //结束动画，数据重置
g_times = 0
arm_step_angle = 1.0 //手臂每一次动画弯曲的角度
body_step_angle = 3.0 //手臂整体每一次动画旋转角度
g_body_angle = -90.0 //手臂整体的旋转角度
g_arm_angle = -45.0 //手臂弯曲的角度
g_isHandleCube = false
g_moveEnd = false
g_modelMatrix.setTranslate(0.0, -12.0, 0.0) //模型矩阵恢复
}

if (g_times < 45) { //第二、第三手臂向下弯
g_arm_angle -= arm_step_angle
} else if (g_times <= 100) { //抓起方块整体旋转
g_isHandleCube = true
g_body_angle = g_body_angle + body_step_angle
} else if (g_times <= 105) { //放下方块，抬起一点第二、第三手臂
g_isHandleCube = false
g_moveEnd = true
g_arm_angle += arm_step_angle
} else if (g_times <= 160) { //手臂整体旋转回来
g_body_angle = g_body_angle - body_step_angle
g_arm_angle += arm_step_angle
} else if (g_times <= 165) { //手臂抬起
g_arm_angle += arm_step_angle
}

draw(gl, n, viewProjMatrix, u_MvpMatrix, u_NormalMatrix, u_VerticesColor)
}
``````

# 2.demo代码

``````<!DOCTYPE html>
<html lang="en">

<meta charset="UTF-8">
<title></title>

<body>
<!--通过canvas标签创建一个800px*800px大小的画布-->
<canvas id="webgl" width="800" height="800"></canvas>
<script type="text/javascript" src="./lib/cuon-matrix.js"></script>
<script>
//顶点着色器
'attribute vec4 a_Position;\\n' + //声明attribute变量a_Position，用来存放顶点位置信息
'attribute vec4 a_Normal;\\n' + //声明attribute变量a_Normal，用来存放法向量
'uniform mat4 u_MvpMatrix;\\n' + //声明uniform变量u_MvpMatrix，用来存放模型视图投影组合矩阵
'uniform mat4 u_NormalMatrix;\\n' + //声明uniform变量u_NormalMatrix，用来存放变换法向量矩阵
'uniform vec3 u_VerticesColor;\\n' + //声明uniform变量u_VerticesColor，用来存放顶点颜色
'varying vec4 v_Color;\\n' + //声明varying变量v_Color，用来向片元着色器传值顶点颜色信息
'void main(){\\n' +
'  gl_Position = u_MvpMatrix * a_Position;\\n' + //将模型视图投影组合矩阵与顶点坐标相乘赋值给顶点着色器内置变量gl_Position
'  vec3 normal = normalize(vec3(u_NormalMatrix * a_Normal));\\n' + //对计算变换后的法向量并归一化处理
'  vec3 lightDirection = normalize(vec3(0.0,0.5,0.7));\\n' + //声明光线方向
'  float nDotL = max(dot(lightDirection, normal), 0.0);\\n' + //计算光线方向和法向量点积
'  vec3 diffuse = u_VerticesColor * nDotL;\\n' + //计算平行光的颜色
'  vec3 ambient = vec3(0.1);\\n' + //声明环境光颜色
'  v_Color = vec4(diffuse + ambient, 1.0);\\n' + //将颜色信息传给片元着色器，
'}\\n'

//片元着色器
'#ifdef GL_ES\\n' +
' precision mediump float;\\n' + // 设置精度
'#endif\\n' +
'varying vec4 v_Color;\\n' + //声明varying变量v_Color，用来接收顶点着色器传送的片元颜色信息
'void main(){\\n' +
//将varying变量v_Color接收的颜色信息赋值给内置变量gl_FragColor
' gl_FragColor = v_Color;\\n' +
'}\\n'

//初始化着色器函数
//创建顶点着色器对象
//创建片元着色器对象
//引入顶点、片元着色器源代码
//编译顶点、片元着色器

//创建程序对象program
var program = gl.createProgram()
//附着顶点着色器和片元着色器到program
//链接program
//使用program
gl.useProgram(program)
gl.program = program
//返回程序program对象
return program
}

function init() {
//通过getElementById()方法获取canvas画布
var canvas = document.getElementById('webgl')
//通过方法getContext()获取WebGL上下文
var gl = canvas.getContext('webgl')
//初始化着色器
console.log('初始化着色器失败')
return
}

// 设置canvas的背景色
gl.clearColor(0.0, 0.0, 0.0, 1.0)

//初始化顶点坐标和顶点颜色
var n = initVertexBuffers(gl)

setMatrixAndDraw(gl, n)

}

//设置矩阵并绘图
function setMatrixAndDraw(gl, n) {

//开启隐藏面消除
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)

//获取顶点着色器uniform变量u_MvpMatrix、u_NormalMatrix,u_VerticesColor的存储地址
var u_MvpMatrix = gl.getUniformLocation(gl.program, 'u_MvpMatrix')
var u_NormalMatrix = gl.getUniformLocation(gl.program, 'u_NormalMatrix')
var u_VerticesColor = gl.getUniformLocation(gl.program, 'u_VerticesColor')

if (!u_MvpMatrix || !u_NormalMatrix || !u_VerticesColor) {
console.log('获取u_MvpMatrix、u_NormalMatrix或u_VerticesColor存储地址失败')
return
}

//设置视图投影矩阵
var viewProjMatrix = new Matrix4()
viewProjMatrix.setPerspective(50.0, 1.0, 1.0, 150.0)
viewProjMatrix.lookAt(60.0, 20.0, 50.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0)

//声明tick函数
var tick = function () {
animate(gl, n, viewProjMatrix, u_MvpMatrix, u_NormalMatrix, u_VerticesColor)
requestAnimationFrame(tick)
}
tick() // 调用tick

}

//声明全局变量
var arm_step_angle = 1.0 //手臂每一次动画弯曲的角度
var body_step_angle = 3.0 //手臂整体每一次动画旋转角度
var g_body_angle = -90.0 //手臂整体的旋转角度
var g_arm_angle = -45.0 //手臂弯曲的角度
var g_isHandleCube = false
var g_moveEnd = false

var g_times = 0

function animate(gl, n, viewProjMatrix, u_MvpMatrix, u_NormalMatrix, u_VerticesColor) {
g_times++
if (g_times > 170) { //结束动画，数据重置
g_times = 0
arm_step_angle = 1.0 //手臂每一次动画弯曲的角度
body_step_angle = 3.0 //手臂整体每一次动画旋转角度
g_body_angle = -90.0 //手臂整体的旋转角度
g_arm_angle = -45.0 //手臂弯曲的角度
g_isHandleCube = false
g_moveEnd = false
g_modelMatrix.setTranslate(0.0, -12.0, 0.0) //模型矩阵恢复
}

if (g_times < 45) { //第二、第三手臂向下弯
g_arm_angle -= arm_step_angle
} else if (g_times <= 100) { //抓起方块整体旋转
g_isHandleCube = true
g_body_angle = g_body_angle + body_step_angle
} else if (g_times <= 105) { //放下方块，抬起一点第二、第三手臂
g_isHandleCube = false
g_moveEnd = true
g_arm_angle += arm_step_angle
} else if (g_times <= 160) { //手臂整体旋转回来
g_body_angle = g_body_angle - body_step_angle
g_arm_angle += arm_step_angle
} else if (g_times <= 165) { //手臂抬起
g_arm_angle += arm_step_angle
}

draw(gl, n, viewProjMatrix, u_MvpMatrix, u_NormalMatrix, u_VerticesColor)
}

function initArrayBuffer(gl, data, num, type, attribute) {
//创建缓冲区对象
var buffer = gl.createBuffer()
//将顶点坐标和顶点颜色信息写入缓冲区对象
gl.bindBuffer(gl.ARRAY_BUFFER, buffer)
gl.bufferData(gl.ARRAY_BUFFER, data, gl.STATIC_DRAW)

//获取顶点着色器attribute变量存储地址, 分配缓存并开启
var a_Attribute = gl.getAttribLocation(gl.program, attribute)
gl.vertexAttribPointer(a_Attribute, num, type, false, 0, 0)
gl.enableVertexAttribArray(a_Attribute)

return true
}
//声明模型变换矩阵和模型视图投影矩阵
var g_modelMatrix = new Matrix4()
var g_mvpMatrix = new Matrix4()

//绘制图形
function draw(gl, n, viewProjMatrix, u_MvpMatrix, u_NormalMatrix, u_VerticesColor) {

gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
gl.uniform3f(u_VerticesColor, 1.0, 0.4, 0.0)

//绘制基座
var baseHeight = 2.0 //基座的高度
g_modelMatrix.setTranslate(0.0, -12.0, 0.0) //设置为平移矩阵，并沿y轴向下移动12
drawBox(gl, n, 10.0, baseHeight, 10.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//方块
var cubeHeight = 2.0 //方块厚度
g_modelMatrix.setTranslate(0.0, -12.0, -16)
drawBox(gl, n, 10.0, cubeHeight, 10.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//第一节胳膊
var arm1Length = 10.0 //第一节胳膊的长度
g_modelMatrix.translate(0.0, baseHeight, 0.0)
g_modelMatrix.rotate(g_body_angle, 0.0, 1.0, 0.0)
drawBox(gl, n, 3.0, arm1Length, 3.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//第二节胳膊
var arm2Length = 16.0
g_modelMatrix.translate(0.0, arm1Length, 0.0) //移至arm1
g_modelMatrix.rotate(g_arm_angle, 0.0, 0.0, 1.0)
drawBox(gl, n, 4.0, arm2Length, 4.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//第三节胳膊
var arm3Length = 10.0
g_modelMatrix.translate(0.0, arm2Length, 0.0) //移至arm2
g_modelMatrix.rotate(g_arm_angle, 0.0, 0.0, 1.0)
drawBox(gl, n, 3.0, arm3Length, 3.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//手掌
var palmLength = 2.0
var handleLength = 8.0
g_modelMatrix.translate(0.0, handleLength, 0.0) //移至arm3
g_modelMatrix.rotate(0.0, 0.0, 1.0, 0.0)
drawBox(gl, n, 6.0, palmLength, 6.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)

//随手臂移动的方块
if (g_isHandleCube) {
gl.uniform3f(u_VerticesColor, 1.0, 0.0, 0.0)
var cubeHeight = 2.0 //方块厚度
g_modelMatrix.translate(0.0, cubeHeight, 0.0)
drawBox(gl, n, 10.0, cubeHeight, 10.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)
} else if (!g_isHandleCube && g_moveEnd) {
g_modelMatrix.setTranslate(0.0, -12.0, -32)
gl.uniform3f(u_VerticesColor, 1.0, 0.4, 0.0)
var cubeHeight = 2.0 //方块厚度
drawBox(gl, n, 10.0, cubeHeight, 10.0, viewProjMatrix, u_MvpMatrix, u_NormalMatrix)
}

}

var g_matrixStack = [] //存储矩阵的数组
function pushMatrix(m) { //将矩阵压入栈
var m2 = new Matrix4(m)
g_matrixStack.push(m2)
}

function popMatrix() { //从栈中弹出矩阵
return g_matrixStack.pop()
}

var g_normalMatrix = new Matrix4() //变换法向量矩阵

//绘制立方体
function drawBox(gl, n, width, height, depth, viewProjMatrix, u_MvpMatrix, u_NormalMatrix) {
pushMatrix(g_modelMatrix) //备份变换前模型矩阵

g_modelMatrix.scale(width, height, depth)
//计算、设置模型视图投影矩阵
g_mvpMatrix.set(viewProjMatrix)
g_mvpMatrix.multiply(g_modelMatrix)
gl.uniformMatrix4fv(u_MvpMatrix, false, g_mvpMatrix.elements)

//计算、设置变换法向量矩阵
g_normalMatrix.setInverseOf(g_modelMatrix)
g_normalMatrix.transpose()
gl.uniformMatrix4fv(u_NormalMatrix, false, g_normalMatrix.elements)

//绘制
gl.drawElements(gl.TRIANGLES, n, gl.UNSIGNED_BYTE, 0)
g_modelMatrix = popMatrix() //将备份的模型矩阵赋值给全局模型矩阵
}

//初始化顶点坐标和顶点颜色
function initVertexBuffers(gl) {

var v0 = [0.5, 1.0, 0.5]
var v1 = [-0.5, 1.0, 0.5]
var v2 = [-0.5, 0.0, 0.5]
var v3 = [0.5, 0.0, 0.5]
var v4 = [0.5, 0.0, -0.5]
var v5 = [0.5, 1.0, -0.5]
var v6 = [-0.5, 1.0, -0.5]
var v7 = [-0.5, 0.0, -0.5]

//顶点
var vertices = new Float32Array([
...v0, ...v1, ...v2, ...v3, // 前
...v0, ...v3, ...v4, ...v5, // 右
...v0, ...v5, ...v6, ...v1, // 上
...v1, ...v6, ...v7, ...v2, // 左
...v7, ...v4, ...v3, ...v2, // 下
...v4, ...v7, ...v6, ...v5 // 后
])

var font = [0.0, 0.0, 1.0]
var back = [0.0, 0.0, -1.0]
var left = [-1.0, 0.0, 0.0]
var right = [1.0, 0.0, 0.0]
var top = [0.0, 1.0, 0.0]
var down = [0.0, -1.0, 0.0]
// 法向量
var normals = new Float32Array([
...font, ...font, ...font, ...font, // v0-v1-v2-v3 前
...right, ...right, ...right, ...right, // v0-v3-v4-v5 右
...top, ...top, ...top, ...top, // v0-v5-v6-v1 上
...left, ...left, ...left, ...left, // v1-v6-v7-v2 左
...down, ...down, ...down, ...down, // v7-v4-v3-v2 下
...back, ...back, ...back, ...back, // v4-v7-v6-v5 后
])

// 绘制的索引
var indices = new Uint8Array([
0, 1, 2, 0, 2, 3, // 前
4, 5, 6, 4, 6, 7, // 右
8, 9, 10, 8, 10, 11, // 上
12, 13, 14, 12, 14, 15, // 左
16, 17, 18, 16, 18, 19, // 下
20, 21, 22, 20, 22, 23 // 后
])

if (!initArrayBuffer(gl, vertices, 3, gl.FLOAT, 'a_Position')) {
return -1
}

if (!initArrayBuffer(gl, normals, 3, gl.FLOAT, 'a_Normal')) {
return -1
}

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

//将顶点索引写入缓冲区对象
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer)
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW)

return indices.length

}

init()
</script>
</body>

</html>
``````