前面写了OpenGLES的入门篇，一些朋友觉得还不错，找到我问了一些知识，这次我有针对性的写下这篇文章，也为我OpenGLES进阶篇做个开始。
我已认证微信，感兴趣朋友可进我个人主页，点击微信小图标加我微信。 代码已传GitHub： https://github.com/qingmomo/OpenGLES
效果如下：
最终结果.png
由于是进阶篇，对基础的介绍就不会那么多了：
绘制立体多边形
绘制多边形我们是需要多边形的顶点数据的，这些数据我从网上下载了一个obj文件，从中取出了3个多边形的顶点数据，并给它加上了颜色数据。 但这些多边形的索引数据，obj里的并不是很清楚(可能是我不会用)，我使用了自己开发项目的代码来构造。关于构造代码，由于公司利益，这里不会给出，直接会使用构造后的结果。
好了，闲话少讲，步入正题：
新建一个自定义的NewOpenGLView继承自UIView，为了能使用openGLES,我们得做一些基础的配置：
代码语言：javascript复制//重写initWithFrame方法便于方法调用
-(instancetype)initWithFrame:(CGRect)frame{
if (self==[super initWithFrame:frame]) {
[self setupLayerAndContext];
[self setupBuffers];
[self setupProgram];
[self render];
}
return self;
} (Class)layerClass{
//OpenGL内容只会在此类layer上描绘
return [CAEAGLLayer class];
}
- (void)setupLayerAndContext
{
_eaglLayer = (CAEAGLLayer*) self.layer;
// CALayer 默认是透明的，必须将它设为不透明才能让其可见,性能最好
_eaglLayer.opaque = YES;
// 设置描绘属性，在这里设置不维持渲染内容以及颜色格式为 RGBA8
_eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:NO], kEAGLDrawablePropertyRetainedBacking, kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat, nil];
// 指定 OpenGLES 渲染API的版本，在这里我们使用OpenGLES 3.0，由于3.0兼容2.0并且功能更强，为何不用更好的呢,不过注意：3.0支持的手机最低为5s，系统最低为iOS7
EAGLRenderingAPI api = kEAGLRenderingAPIOpenGLES3;
_context = [[EAGLContext alloc] initWithAPI:api];
if (!_context) {
NSLog(@"Failed to initialize OpenGLES 3.0 context");
}
// 设置为当前上下文
[EAGLContext setCurrentContext:_context];
}
-(void)setupBuffers{
// 1.depth
glGenRenderbuffers(1, &_depthBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _depthBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, self.frame.size.width, self.frame.size.height);
// 2.color
glGenRenderbuffers(1, &_colorBuffer); //生成和绑定render buffer的API函数
glBindRenderbuffer(GL_RENDERBUFFER, _colorBuffer);
//为其分配空间
[_context renderbufferStorage:GL_RENDERBUFFER fromDrawable:_eaglLayer];
// 3.frame
glGenFramebuffers(1, &_frameBuffer); //生成和绑定frame buffer的API函数
glBindFramebuffer(GL_FRAMEBUFFER, _frameBuffer);
//将renderbuffer跟framebuffer进行绑定
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _colorBuffer);
//将depthBuffer跟frame buffer进行绑
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthBuffer);
}上面所涉及的变量都在类声明的扩展中定义，以下是全部变量定义：
代码语言：javascript复制@interface NewOpenGLView ()
{
CAEAGLLayer *_eaglLayer;
EAGLContext *_context;
GLuint _depthBuffer;
GLuint _colorBuffer;
GLuint _frameBuffer;
GLuint _programHandle; //着色器程序
GLuint _positionSlot; //顶点槽位
GLuint _colorSlot; //颜色槽位
GLuint _projectionSlot; //投影矩阵槽位
GLuint _modelViewSlot; //模型矩阵槽位
GLKMatrix4 _projectionMatrix; //投影矩阵
GLKMatrix4 _modelViewMatrix; //模型(其实是观察)矩阵
//纹理
GLuint _textureProgram;
GLuint _texPositionSlot; //顶点槽位
GLuint _texCoordSlot; //纹理坐标槽位
GLuint _ourTextureSlot; //纹理采样对象槽位
GLuint _texProjectionSlot; //投影矩阵槽位
GLuint _texModelViewSlot; //模型矩阵槽位
GLKMatrix4 _texProjectionMatrix; //投影矩阵
GLKMatrix4 _texModelViewMatrix; //模型(其实是观察)矩阵
//3个纹理对象
GLuint _textureID1; //纹理对象
GLuint _textureID2; //纹理对象
GLuint _textureID3; //纹理对象
}
@endDemo中还使用了入门篇中详细介绍过的2个工具类： GLESUtils类 ：配置着色器程序 TextureManager类 ：配置纹理图片
接下来我们介绍如何配置着色器程序： 在入门篇里，我们要么只绘制图形，要么只绘制纹理，没有把它们结合起来绘制过，而这里我们需要把他们结合起来绘制。这个时候，glsl语言的写法就有区别了，可以把它们写在同一个文件里，也可以分别写出来，这里我是分别写出了图形所对应的VertexShader.glsl、FragmentShader.glsl和纹理所对应的TextureVertex.glsl、TextureFragment.glsl。
先来介绍绘制图形的glsl语言（Vertex和Fragment）：
代码语言：javascript复制uniform mat4 projection;
uniform mat4 modelView;
attribute vec4 vPosition;
attribute vec4 vSourceColor;
varying vec4 vDestinationColor;
void main(void)
{
gl_Position = projection * modelView * vPosition;
vDestinationColor = vSourceColor;
}precision medium float;
varying vec4 vDestinationColor;
void main()
{
gl_FragColor = vDestinationColor;
}关于shader语言这里就不多赘述了。 然后我们配置图形着色器程序：
代码语言：javascript复制-(void)setupProgram{
//1.多边体program
NSString *vertexShaderPath = [[NSBundle mainBundle] pathForResource:@"VertexShader"
ofType:@"glsl"];
NSString *fragmentShaderPath = [[NSBundle mainBundle] pathForResource:@"FragmentShader"
ofType:@"glsl"];
_programHandle = [GLESUtils loadProgram:vertexShaderPath withFragmentShaderFilepath:fragmentShaderPath];
//获取槽位
_positionSlot = glGetAttribLocation(_programHandle, "vPosition");
_colorSlot = glGetAttribLocation(_programHandle, "vSourceColor");
_projectionSlot = glGetUniformLocation(_programHandle, "projection");
_modelViewSlot = glGetUniformLocation(_programHandle, "modelView");
glEnableVertexAttribArray(_positionSlot);
glEnableVertexAttribArray(_colorSlot);
}着色器程序配置好，我们还需设置着色器里的投影矩阵和观察矩阵(这里是观察矩阵,根据功能理解为模型矩阵其实也没差):
代码语言：javascript复制-(void)setupProjectionMatrixAndModelViewMatrix{
//1.多边体
float aspect = self.frame.size.width/self.frame.size.height;
_projectionMatrix = GLKMatrix4MakePerspective(45.0*M_PI/180.0, aspect, 0.1, 100);
glUniformMatrix4fv(_projectionSlot, 1, GL_FALSE, _projectionMatrix.m);
_modelViewMatrix = GLKMatrix4MakeTranslation(0, 0, -5); //平移
_modelViewMatrix = GLKMatrix4RotateX(_modelViewMatrix, 0.6); //旋转X轴，0.6是弧度值
glUniformMatrix4fv(_modelViewSlot, 1, GL_FALSE, _modelViewMatrix.m);
}做完这些，我们就可以开始绘制了:
代码语言：javascript复制-(void)render
{
//设置清屏颜色,默认是黑色，如果你的运行结果是黑色，问题就可能在这儿
glClearColor(0.3, 0.5, 0.8, 1.0);
/*
glClear指定清除的buffer
共可设置三个选项GL_COLOR_BUFFER_BIT，GL_DEPTH_BUFFER_BIT和GL_STENCIL_BUFFER_BIT
也可组合如:glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
*/
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Setup viewport
glViewport(0, 0, self.frame.size.width, self.frame.size.height);
[_context presentRenderbuffer:_colorBuffer];
}做到这里，我们运行Demo，得到的结果应该是这样的：
初始结果.png
下面我们开始构造立体多边形的数据（x,y,z,r,g,b,a）并绘制出来(Demo使用最基本的数据格式，如需优化，请自行构造buffer、VAO)：
代码语言：javascript复制-(void)drawFirstCube{
//顶点数据
GLfloat ver[] = {
-0.508680,0.260000,-0.725382,0.345678,0.678943,0.812332,0.900000,
0.306216,0.260000,-0.725382,0.345678,0.678943,0.812332,0.900000,
0.306216,0.260000,-0.244226,0.345678,0.678943,0.812332,0.900000,
-0.508680,0.260000,-0.244226,0.345678,0.678943,0.812332,0.900000,
-0.508680,0.010000,-0.725382,0.345678,0.678943,0.812332,0.900000,
0.306216,0.010000,-0.725382,0.345678,0.678943,0.812332,0.900000,
0.306216,0.010000,-0.244226,0.345678,0.678943,0.812332,0.900000,
-0.508680,0.010000,-0.244226,0.345678,0.678943,0.812332,0.900000,
};
//顶面和底面索引
GLubyte ind_top[] = {
3,0,1,1,2,3,
};
GLubyte ind_bot[] = {// 4是因为数据是顶面底面一起的，顶面数据4个，底面4个
3 4,0 4,1 4,1 4,2 4,3 4,
};
//侧面索引
GLubyte side[] = {
0,4,1,5,2,6,3,7,0,4,
};
// 绘制
// 顶面
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver 3);
glDrawElements(GL_TRIANGLES, sizeof(ind_top)/sizeof(GLubyte), GL_UNSIGNED_BYTE, ind_top);
// 底面
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver 3);
glDrawElements(GL_TRIANGLES, sizeof(ind_bot)/sizeof(GLubyte), GL_UNSIGNED_BYTE, ind_bot);
// 侧面
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver 3);
glDrawElements(GL_TRIANGLE_STRIP, sizeof(side)/sizeof(GLubyte), GL_UNSIGNED_BYTE, side);
//需要画的线 顶面和底面线
GLfloat line[] = {
-0.508680,0.260000,-0.725382,0.965789,0.677845,0.812332,1.0,
0.306216,0.260000,-0.725382,0.965789,0.677845,0.812332,1.0,
0.306216,0.260000,-0.244226,0.965789,0.677845,0.812332,1.0,
-0.508680,0.260000,-0.244226,0.965789,0.677845,0.812332,1.0,
-0.508680,0.010000,-0.725382,0.965789,0.677845,0.812332,1.0,
0.306216,0.010000,-0.725382,0.965789,0.677845,0.812332,1.0,
0.306216,0.010000,-0.244226,0.965789,0.677845,0.812332,1.0,
-0.508680,0.010000,-0.244226,0.965789,0.677845,0.812332,1.0,
};
GLubyte line_top[] = {
0,1,2,3,
};
GLubyte line_bot[] = { // 4是因为数据是顶面底面一起的，顶面数据4个，底面4个
0 4,1 4,2 4,3 4,
};
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line 3);
glDrawElements(GL_LINE_LOOP, sizeof(line_top)/sizeof(GLubyte), GL_UNSIGNED_BYTE, line_top);
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line 3);
glDrawElements(GL_LINE_LOOP, sizeof(line_bot)/sizeof(GLubyte), GL_UNSIGNED_BYTE, line_bot);
}数据不算太复杂，太复杂了我也没想法去处理构造它，在顶点数据中，我们集合了顶面顶点数据和底面顶点数据，然后分别构造出它顶面和底面需要绘制的三角形索引，最后还有它需要绘制的侧面的所有三角形索引。 绘制的时候根据顶面、底面、侧面使用合适的glDraw方法绘制，为什么后面还会绘制顶面和底面的线呢，这是因为如果不绘制线的话，绘出来结果会不够理想，让人区分不出来这是立方体。
不画线.png
画线.png
然后我们以同样的方式分别绘制第二、第三个多边体：
代码语言：javascript复制-(void)drawSecondCube{
//顶点数据
GLfloat ver[] = {
-0.304217,0.260000,0.814439,0.345678,0.678943,0.465789,0.900000,
-0.304217,0.260000,0.344297,0.345678,0.678943,0.465789,0.900000,
0.429602,0.260000,0.344297,0.345678,0.678943,0.465789,0.900000,
0.426395,0.260000,0.718223,0.345678,0.678943,0.465789,0.900000,
0.169820,0.260000,0.718223,0.345678,0.678943,0.465789,0.900000,
0.169820,0.260000,0.814439,0.345678,0.678943,0.465789,0.900000,
-0.304217,0.010000,0.814439,0.345678,0.678943,0.465789,0.900000,
-0.304217,0.010000,0.344297,0.345678,0.678943,0.465789,0.900000,
0.429602,0.010000,0.344297,0.345678,0.678943,0.465789,0.900000,
0.426395,0.010000,0.718223,0.345678,0.678943,0.465789,0.900000,
0.169820,0.010000,0.718223,0.345678,0.678943,0.465789,0.900000,
0.169820,0.010000,0.814439,0.345678,0.678943,0.465789,0.900000,
};
//顶面和底面索引
GLubyte ind_top[] = {
5,0,1,1,2,3,4,5,1,1,3,4,
};
GLubyte ind_bot[] = {
5 6,0 6,1 6,1 6,2 6,3 6,4 6,5 6,1 6,1 6,3 6,4 6,
};
//侧面索引
GLubyte side[] = {
0,6,1,7,2,8,3,9,4,10,5,11,0,6,
};
// 绘制
// 顶面
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver 3);
glDrawElements(GL_TRIANGLES, sizeof(ind_top)/sizeof(GLubyte), GL_UNSIGNED_BYTE, ind_top);
// 底面
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver 3);
glDrawElements(GL_TRIANGLES, sizeof(ind_bot)/sizeof(GLubyte), GL_UNSIGNED_BYTE, ind_bot);
// 侧面
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver 3);
glDrawElements(GL_TRIANGLE_STRIP, sizeof(side)/sizeof(GLubyte), GL_UNSIGNED_BYTE, side);
//需要画的线
GLfloat line[] = {
-0.304217,0.260000,0.814439,0.965789,0.678943,0.465789,1.000000,
-0.304217,0.260000,0.344297,0.965789,0.678943,0.465789,1.000000,
0.429602,0.260000,0.344297,0.965789,0.678943,0.465789,1.000000,
0.426395,0.260000,0.718223,0.965789,0.678943,0.465789,1.000000,
0.169820,0.260000,0.718223,0.965789,0.678943,0.465789,1.000000,
0.169820,0.260000,0.814439,0.965789,0.678943,0.465789,1.000000,
-0.304217,0.010000,0.814439,0.965789,0.678943,0.465789,1.000000,
-0.304217,0.010000,0.344297,0.965789,0.678943,0.465789,1.000000,
0.429602,0.010000,0.344297,0.965789,0.678943,0.465789,1.000000,
0.426395,0.010000,0.718223,0.965789,0.678943,0.465789,1.000000,
0.169820,0.010000,0.718223,0.965789,0.678943,0.465789,1.000000,
0.169820,0.010000,0.814439,0.965789,0.678943,0.465789,1.000000,
};
GLubyte line_top[] = {
0,1,2,3,4,5,
};
GLubyte line_bot[] = {
0 6,1 6,2 6,3 6,4 6,5 6,
};
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line 3);
glDrawElements(GL_LINE_LOOP, sizeof(line_top)/sizeof(GLubyte), GL_UNSIGNED_BYTE, line_top);
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line 3);
glDrawElements(GL_LINE_LOOP, sizeof(line_bot)/sizeof(GLubyte), GL_UNSIGNED_BYTE, line_bot);
}
-(void)drawThirdCube{
//顶点数据
GLfloat ver[] = {
0.306216,0.260000,-0.725382,0.778943,0.378943,0.465789,0.900000,
0.429602,0.260000,-0.725382,0.778943,0.378943,0.465789,0.900000,
0.602136,0.260000,-0.725382,0.778943,0.378943,0.465789,0.900000,
0.602136,0.260000,-0.816786,0.778943,0.378943,0.465789,0.900000,
0.987652,0.260000,-0.816786,0.778943,0.378943,0.465789,0.900000,
0.987652,0.260000,-0.430321,0.778943,0.378943,0.465789,0.900000,
0.901058,0.260000,-0.430321,0.778943,0.378943,0.465789,0.900000,
0.901058,0.260000,-0.319931,0.778943,0.378943,0.465789,0.900000,
0.622946,0.260000,-0.319931,0.778943,0.378943,0.465789,0.900000,
0.306216,0.260000,-0.319931,0.778943,0.378943,0.465789,0.900000,
0.306216,0.010000,-0.725382,0.778943,0.378943,0.465789,0.900000,
0.429602,0.010000,-0.725382,0.778943,0.378943,0.465789,0.900000,
0.602136,0.010000,-0.725382,0.778943,0.378943,0.465789,0.900000,
0.602136,0.010000,-0.816786,0.778943,0.378943,0.465789,0.900000,
0.987652,0.010000,-0.816786,0.778943,0.378943,0.465789,0.900000,
0.987652,0.010000,-0.430321,0.778943,0.378943,0.465789,0.900000,
0.901058,0.010000,-0.430321,0.778943,0.378943,0.465789,0.900000,
0.901058,0.010000,-0.319931,0.778943,0.378943,0.465789,0.900000,
0.622946,0.010000,-0.319931,0.778943,0.378943,0.465789,0.900000,
0.306216,0.010000,-0.319931,0.778943,0.378943,0.465789,0.900000,
};
//顶面和底面索引
GLubyte ind_top[] = {
9,0,1,2,3,4,4,5,6,6,7,8,8,9,1,2,4,6,6,8,1,1,2,6,
};
GLubyte ind_bot[] = {
9 10,0 10,1 10,2 10,3 10,4 10,4 10,5 10,6 10,6 10,7 10,8 10,8 10,9 10,1 10,2 10,4 10,6 10,6 10,8 10,1 10,1 10,2 10,6 10,
};
//侧面索引
GLubyte side[] = {
0,10,1,11,2,12,3,13,4,14,5,15,6,16,7,17,8,18,9,19,0,10,
};
// 绘制
// 顶面
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver 3);
glDrawElements(GL_TRIANGLES, sizeof(ind_top)/sizeof(GLubyte), GL_UNSIGNED_BYTE, ind_top);
// 底面
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver 3);
glDrawElements(GL_TRIANGLES, sizeof(ind_bot)/sizeof(GLubyte), GL_UNSIGNED_BYTE, ind_bot);
// 侧面
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), ver 3);
glDrawElements(GL_TRIANGLE_STRIP, sizeof(side)/sizeof(GLubyte), GL_UNSIGNED_BYTE, side);
//需要画的线
GLfloat line[] = {
0.306216,0.260000,-0.725382,0.345678,0.678943,0.465789,1.000000,
0.429602,0.260000,-0.725382,0.345678,0.678943,0.465789,1.000000,
0.602136,0.260000,-0.725382,0.345678,0.678943,0.465789,1.000000,
0.602136,0.260000,-0.816786,0.345678,0.678943,0.465789,1.000000,
0.987652,0.260000,-0.816786,0.345678,0.678943,0.465789,1.000000,
0.987652,0.260000,-0.430321,0.345678,0.678943,0.465789,1.000000,
0.901058,0.260000,-0.430321,0.345678,0.678943,0.465789,1.000000,
0.901058,0.260000,-0.319931,0.345678,0.678943,0.465789,1.000000,
0.622946,0.260000,-0.319931,0.345678,0.678943,0.465789,1.000000,
0.306216,0.260000,-0.319931,0.345678,0.678943,0.465789,1.000000,
0.306216,0.010000,-0.725382,0.345678,0.678943,0.465789,1.000000,
0.429602,0.010000,-0.725382,0.345678,0.678943,0.465789,1.000000,
0.602136,0.010000,-0.725382,0.345678,0.678943,0.465789,1.000000,
0.602136,0.010000,-0.816786,0.345678,0.678943,0.465789,1.000000,
0.987652,0.010000,-0.816786,0.345678,0.678943,0.465789,1.000000,
0.987652,0.010000,-0.430321,0.345678,0.678943,0.465789,1.000000,
0.901058,0.010000,-0.430321,0.345678,0.678943,0.465789,1.000000,
0.901058,0.010000,-0.319931,0.345678,0.678943,0.465789,1.000000,
0.622946,0.010000,-0.319931,0.345678,0.678943,0.465789,1.000000,
0.306216,0.010000,-0.319931,0.345678,0.678943,0.465789,1.000000,
};
GLubyte line_top[] = {
0,1,2,3,4,5,6,7,8,9,
};
GLubyte line_bot[] = {
0 10,1 10,2 10,3 10,4 10,5 10,6 10,7 10,8 10,9 10,
};
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line 3);
glDrawElements(GL_LINE_LOOP, sizeof(line_top)/sizeof(GLubyte), GL_UNSIGNED_BYTE, line_top);
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), line 3);
glDrawElements(GL_LINE_LOOP, sizeof(line_bot)/sizeof(GLubyte), GL_UNSIGNED_BYTE, line_bot);
}我们在render方法里调用方法绘制这三个多边体，这时render该是这样的：
代码语言：javascript复制-(void)render
{
//设置清屏颜色,默认是黑色，如果你的运行结果是黑色，问题就可能在这儿
glClearColor(0.3, 0.5, 0.8, 1.0);
/*
glClear指定清除的buffer
共可设置三个选项GL_COLOR_BUFFER_BIT，GL_DEPTH_BUFFER_BIT和GL_STENCIL_BUFFER_BIT
也可组合如:glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
*/
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Setup viewport
glViewport(0, 0, self.frame.size.width, self.frame.size.height);
//开启深度测试
glEnable(GL_DEPTH_TEST);
//绘制3个多边体
glUseProgram(_programHandle);
[self setupProjectionMatrixAndModelViewMatrix];
[self drawFirstCube];
[self drawSecondCube];
[self drawThirdCube];
[_context presentRenderbuffer:_colorBuffer];
}我们在绘制多边体前先开启了深度测试，然后使用多边体着色器程序，再配置多边体的投影和观察矩阵，注意每次使用program后需要重新配置矩阵。 做完这些，运行结果如下：
三个多边体.png
绘制纹理
然后...我们再把纹理绘制上去,要绘纹理，我们得设置纹理的着色器语言（Vertex和Fragment）:
代码语言：javascript复制attribute vec4 Position;
attribute vec2 TexCoordIn;
varying vec2 TexCoordOut;
uniform mat4 Projection;
uniform mat4 ModelView;
void main(){
gl_Position = Projection * ModelView * Position;
TexCoordOut = vec2(TexCoordIn.x, TexCoordIn.y);
}uniform sampler2D ourTexture;
varying mediump vec2 TexCoordOut;
void main(){
gl_FragColor = texture2D(ourTexture, TexCoordOut);
}然后代码配置着色器程序,整个setupProgram方法变为:
代码语言：javascript复制-(void)setupProgram{
//1.多边体program
NSString *vertexShaderPath = [[NSBundle mainBundle] pathForResource:@"VertexShader"
ofType:@"gals"];
NSString *fragmentShaderPath = [[NSBundle mainBundle] pathForResource:@"FragmentShader"
ofType:@"gals"];
_programHandle = [GLESUtils loadProgram:vertexShaderPath withFragmentShaderFilepath:fragmentShaderPath];
//获取槽位
_positionSlot = glGetAttribLocation(_programHandle, "vPosition");
_colorSlot = glGetAttribLocation(_programHandle, "vSourceColor");
_projectionSlot = glGetUniformLocation(_programHandle, "projection");
_modelViewSlot = glGetUniformLocation(_programHandle, "modelView");
glEnableVertexAttribArray(_positionSlot);
glEnableVertexAttribArray(_colorSlot);
// ------------------------------------------------------------------------
//2.纹理program
NSString *texVertexPath = [[NSBundle mainBundle] pathForResource:@"TextureVertex"
ofType:@"glsl"];
NSString *texFragmentPath = [[NSBundle mainBundle] pathForResource:@"TextureFragment"
ofType:@"glsl"];
_textureProgram = [GLESUtils loadProgram:texVertexPath withFragmentShaderFilepath:texFragmentPath];
//获取槽位
_texPositionSlot = glGetAttribLocation(_textureProgram, "Position");
_texCoordSlot = glGetAttribLocation(_textureProgram, "TexCoordIn");
glEnableVertexAttribArray(_texPositionSlot);
glEnableVertexAttribArray(_texCoordSlot);
_ourTextureSlot = glGetUniformLocation(_textureProgram, "ourTexture");
_texProjectionSlot = glGetUniformLocation(_textureProgram, "Projection");
_texModelViewSlot = glGetUniformLocation(_textureProgram, "ModelView");
//获取纹理对象
_textureID1 = [TextureManager getTextureImage:[UIImage imageNamed:@"猫头鹰"]];
_textureID2 = [TextureManager getTextureImage:[UIImage imageNamed:@"乌龟"]];
_textureID3 = [TextureManager getTextureImage:[UIImage imageNamed:@"变色龙"]];
}接着新建一个方法来配置纹理的投影和观察矩阵:
代码语言：javascript复制-(void)setupTextureProjectionMatrixAndModelViewMatrix{
//2.纹理
float aspect = self.frame.size.width/self.frame.size.height;
_texProjectionMatrix = GLKMatrix4MakePerspective(45.0*M_PI/180.0, aspect, 0.1, 100);
glUniformMatrix4fv(_texProjectionSlot, 1, GL_FALSE, _texProjectionMatrix.m);
_texModelViewMatrix = GLKMatrix4MakeTranslation(0, 0, -5); //平移
_texModelViewMatrix = GLKMatrix4RotateX(_texModelViewMatrix, 1.4); //旋转X轴
glUniformMatrix4fv(_texModelViewSlot, 1, GL_FALSE, _texModelViewMatrix.m);
}再接下来，我们就需要构造纹理数据并绘制出来了，对于纹理顶点的坐标数据，由于不知道多边体的中心点在何处，我就自己构造了：
代码语言：javascript复制// 第一个
GLfloat vertices1[] = {
// x y z
-0.9, 0.3, -0.9, //左下
-0.6, 0.3, -0.9, //右下
-0.9, 0.3, -0.6, //左上
-0.6, 0.3, -0.6, //右上
};
// 第二个
GLfloat vertices2[] = {
// x y z
-0.5, 0.3, -0.5, //左下
-0.2, 0.3, -0.5, //右下
-0.5, 0.3, -0.2, //左上
-0.2, 0.3, -0.2, //右上
};
// 第三个
GLfloat vertices3[] = {
// x y z
-0.9, 0.3, -0.1, //左下
-0.6, 0.3, -0.1, //右下
-0.9, 0.3, 0.2, //左上
-0.6, 0.3, 0.2, //右上
};而对于纹理的纹理坐标数据，都是：
代码语言：javascript复制//纹理4个顶点对应纹理坐标，三个都是一样的
GLfloat textureCoord[] = {
0, 0,
1, 0,
0, 1,
1, 1,
};整个方法里构造加上绘制，代码如下：
代码语言：javascript复制//绘制纹理
-(void)drawTextrue{
// 构造3个纹理的顶点坐标
//四个顶点(分别表示xyz轴)
// 第一个
GLfloat vertices1[] = {
// x y z
-0.9, 0.3, -0.9, //左下
-0.6, 0.3, -0.9, //右下
-0.9, 0.3, -0.6, //左上
-0.6, 0.3, -0.6, //右上
};
// 第二个
GLfloat vertices2[] = {
// x y z
-0.5, 0.3, -0.5, //左下
-0.2, 0.3, -0.5, //右下
-0.5, 0.3, -0.2, //左上
-0.2, 0.3, -0.2, //右上
};
// 第三个
GLfloat vertices3[] = {
// x y z
-0.9, 0.3, -0.1, //左下
-0.6, 0.3, -0.1, //右下
-0.9, 0.3, 0.2, //左上
-0.6, 0.3, 0.2, //右上
};
//纹理4个顶点对应纹理坐标，三个都是一样的
GLfloat textureCoord[] = {
0, 0,
1, 0,
0, 1,
1, 1,
};
//绘制
glVertexAttribPointer(_texPositionSlot, 3, GL_FLOAT, GL_FALSE, 0, vertices1);
glVertexAttribPointer(_texCoordSlot, 2, GL_FLOAT, GL_FALSE, 0, textureCoord);
//使用纹理单元
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, _textureID1);
glUniform1i(_ourTextureSlot, 0);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glVertexAttribPointer(_texPositionSlot, 3, GL_FLOAT, GL_FALSE, 0, vertices2);
glVertexAttribPointer(_texCoordSlot, 2, GL_FLOAT, GL_FALSE, 0, textureCoord);
//使用纹理单元
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, _textureID2);
glUniform1i(_ourTextureSlot, 0);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glVertexAttribPointer(_texPositionSlot, 3, GL_FLOAT, GL_FALSE, 0, vertices3);
glVertexAttribPointer(_texCoordSlot, 2, GL_FLOAT, GL_FALSE, 0, textureCoord);
//使用纹理单元
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, _textureID3);
glUniform1i(_ourTextureSlot, 0);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}然后我们在render方法里调用纹理绘制的方法:
代码语言：javascript复制//绘制纹理
glUseProgram(_textureProgram);
[self setupTextureProjectionMatrixAndModelViewMatrix];
[self drawTextrue];得到最终的绘制结果：
最终结果.png
从上面的图片我们能看出来，效果是不够好的，比如边、线锯齿，多边体和纹理模糊，也没有进行矩阵变换重绘等问题，这些涉及到公司产品的竞争，我目前不会分享出来，还请自行寻找解决方案。
最后，给出整个个Demo的目录结构吧
整个Demo目录结构.png
