#import"ViewController.h"
@interface ViewController()
@property(nonatomic,strong)EAGLContext * mContext;// OpenGL的上下文
@property(nonatomic,strong)GLKBaseEffect * mEffect;// OpenGL的着色器
@property(nonatomic,assign)int mCount;
@end
创建OpenGL的上下文和着色器
（1）创建OpenGL上下文
self.mContext= [[EAGLContext alloc]initWithAPI:kEAGLRenderingAPIOpenGLES2];//2.0，还有1.0和3.0
GLKView* view = (GLKView*)self.view;//storyboard记得添加
view.context=self.mContext;
view.drawableColorFormat=GLKViewDrawableColorFormatRGBA8888;//颜色缓冲区格式
[EAGLContext setCurrentContext:self.mContext];
(2)创建顶点数据
//顶点数据，前三个是顶点坐标，后面两个是纹理坐标
GLfloat squareVertexData[] =
{
0.5, -0.5,0.0f,1.0f,0.0f,//右下
-0.5,0.5,0.0f,0.0f,1.0f,//左上
-0.5, -0.5,0.0f,0.0f,0.0f,//左下
//0.5, 0.5, -0.0f,1.0f, 1.0f, //右上
};
//顶点索引，数组中的每三个代表了顶点数组中的顶点比如0，1，2表示取得是0.5, -0.5,0.0f,1.0f,0.0f,//右下，-0.5,0.5,0.0f,0.0f,1.0f,//左上，-0.5, -0.5,0.0f,0.0f,0.0f,//左下这三个点
GLuint indices[] =
{
0,1,2,
//1, 3, 0
};
self.mCount=sizeof(indices) /sizeof(GLuint);
//顶点数据缓存
GLuint buffer;//
glGenBuffers(1, &buffer);// OpenGL为图形处理器控制的缓存生成一个独一无二的标识符
glBindBuffer(GL_ARRAY_BUFFER, buffer);// 为接下来的运算使用一个缓存
glBufferData(GL_ARRAY_BUFFER,sizeof(squareVertexData), squareVertexData,GL_STATIC_DRAW);// 为当前的缓存分配并初始化足够的连续内存
// 顶点索引缓存
GLuint index;
glGenBuffers(1, &index);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, index);
glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof(indices), indices,GL_STATIC_DRAW);
glEnableVertexAttribArray(GLKVertexAttribPosition);// 告诉OpenGL是否使用缓存中的数据
glVertexAttribPointer(GLKVertexAttribPosition,3,GL_FLOAT,GL_FALSE,sizeof(GLfloat) *5, (GLfloat*)NULL+0);// 告诉OpenGL在缓存中数据的类型和所需要访问数据的偏移量
//纹理贴图
NSString* filePath = [[NSBundlemainBundle]pathForResource:@"for_test"ofType:@"jpg"];
NSDictionary* options = [NSDictionarydictionaryWithObjectsAndKeys:@(1),GLKTextureLoaderOriginBottomLeft,nil];//GLKTextureLoaderOriginBottomLeft纹理坐标系是相反的
GLKTextureInfo* textureInfo = [GLKTextureLoadertextureWithContentsOfFile:filePathoptions:optionserror:nil];
//着色器
self.mEffect= [[GLKBaseEffectalloc]init];
self.mEffect.texture2d0.enabled=GL_TRUE;
self.mEffect.texture2d0.name= textureInfo.name;
- (void)glkView:(GLKView*)view drawInRect:(CGRect)rect {
glClearColor(0.3f,0.6f,0.5f,1.0f);
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
//启动着色器
[self.mEffect prepareToDraw];
glDrawElements(GL_TRIANGLES,self.mCount,GL_UNSIGNED_INT,0);
}
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