专业网站建设代理/友情链接2598

  

OpenGL 中任何复杂的图形都是由点,线 和三角形组成的. 那么一个矩形 就需要有两个三角形组成.

纹理, 可以理解为一张图片, 我么可以将整张or部分图片绘制到圆形, 矩形等目标图形中. 

 

下图表示了顶点数据 对应 的纹理中的点.

左侧代表定点数据, 其坐标原点是屏幕中央 ; 右侧图片(纹理), 坐标原点是左下角

 

GLKBaseEffect让我们避开了写shader Language 着色器语言, 相当于对glsl的封装

 

typedef struct {GLKVector3 positonCoords;//顶点GLKVector2 textureCoords;//纹理
}SceneVertex;@interface GLViewController ()@property(nonatomic,strong)GLKBaseEffect *baseEffect;
@property(nonatomic,assign)GLuint vertexBufferID;//缓存ID属性

@end@implementation GLViewController- (void)viewDidLoad {[super viewDidLoad];// Do any additional setup after loading the view.//1.创建OpenGLE ES上下文GLKView *view = (GLKView *)self.view;view.context = [[EAGLContext alloc]initWithAPI:kEAGLRenderingAPIOpenGLES2];[EAGLContext setCurrentContext:view.context];//2.GLKBaseEffect属性, 使我们不需要编写shader language(着色器)代码就可以简单完成绘制self.baseEffect = [[GLKBaseEffect alloc]init];self.baseEffect.useConstantColor = GL_TRUE;//使用静态颜色绘制self.baseEffect.constantColor = GLKVector4Make(1.0f, 1.0f, 1.0f, 1.0f);//设置绘制颜色 rgbaglClearColor(0.0f, 0.0f, 0.0f, 1.0f);//背景颜色//3.定点数据//矩形的六个顶点static const SceneVertex vertices[] = {{{1, -1, 0.0f,},{1.0f,0.0f}}, //右下{{1, 1,  0.0f},{1.0f,1.0f}}, //右上{{-1, 1, 0.0f},{0.0f,1.0f}}, //左上
        {{1, -1, 0.0f},{1.0f,0.0f}}, //右下{{-1, 1, 0.0f},{0.0f,1.0f}}, //左上{{-1, -1, 0.0f},{0.0f,0.0f}}, //左下
    };//4.生成缓存,并为缓存提供数据glGenBuffers(1, &_vertexBufferID);//申请一个标识符glBindBuffer(GL_ARRAY_BUFFER, _vertexBufferID);//将标识符绑定到GL_ARRAY_BUFFERglBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);//复制定点数据从CPU 到 GPU
    glEnableVertexAttribArray(GLKVertexAttribPosition);//顶点缓存数据glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(SceneVertex), NULL + offsetof(SceneVertex, positonCoords));glEnableVertexAttribArray(GLKVertexAttribTexCoord0);glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(SceneVertex), NULL + offsetof(SceneVertex, textureCoords));//5.生成纹理//使用GLkit中的GLKTextureInfo方便的生成图片纹理。CGImageRef imageRef = [[UIImage imageNamed:@"1.png"]CGImage];//GLKTextureInfo封装了纹理缓存的信息，包括是否包含MIP贴图//option 防止图片是倒立了，这个是因为CoreGraphics的坐标系问题NSDictionary* options = [NSDictionary dictionaryWithObjectsAndKeys:@(1), GLKTextureLoaderOriginBottomLeft, nil];GLKTextureInfo *textureInfo = [GLKTextureLoader textureWithCGImage:imageRef options:options error:nil];self.baseEffect.texture2d0.name = textureInfo.name;self.baseEffect.texture2d0.target = textureInfo.target;//6.代理, 绘制
    
}//系统给我们回调的绘制消息，该方法会一直被调用，和display方法一致
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect{//清除背景色glClearColor(0.0f,0.0f,0.0f,1.0f);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);[self.baseEffect prepareToDraw];glDrawArrays(GL_TRIANGLES, 0, 6);}- (void)dealloc{GLKView *view = (GLKView *)self.view;[EAGLContext setCurrentContext:view.context];if (_vertexBufferID != 0) {glDeleteBuffers(1, &_vertexBufferID);_vertexBufferID = 0;}}@end