iOS OpenGL ES簡單繪製三角形

 

OpenGL 是用於2D/3D圖形編程的一套基於C語言的統一接口. windows,Linux,Unix上都可兼容.

OpenGL ES 是在OpenGL嵌入式設備上的版本, android/iOS 等. 在iOS平臺上OpenGL有三個版本OpenGL 1.0/2.0/3.0

基本原理, 能夠經過OpenGL ES驅動GPU圖形處理器 實現圖形編程.

 

在iOS上, 基於GLKit,  對OpenGL ES 的再次封裝, 輔助咱們快速的使用OpenGL ES

//完成一個簡單的繪製, 三角形

typedef struct {
    GLKVector3 positonCoords;
}sceneVertex;

@interface GLViewController ()

@property(nonatomic,strong)GLKBaseEffect *baseEffect;
@property(nonatomic,assign)GLuint vertexBufferID;//緩存ID屬性

@end

@implementation GLViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    //1.建立OpenGLE ES上下文
    GLKView *view = (GLKView *)self.view;
    view.context = [[EAGLContext alloc]initWithAPI:kEAGLRenderingAPIOpenGLES2];
    [EAGLContext setCurrentContext:view.context];
    
    //2.GLKBaseEffect屬性, 使咱們不須要編寫shader language(着色器)代碼就能夠簡單完成繪製
    self.baseEffect = [[GLKBaseEffect alloc]init];
    self.baseEffect.useConstantColor = GL_TRUE;//使用靜態顏色繪製
    self.baseEffect.constantColor = GLKVector4Make(1.0f, 1.0f, 1.0f, 1.0f);//設置繪製顏色 rgba
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);//背景顏色
    
    //3.定點數據
    static const sceneVertex vertices[] = {
        {{-0.5f,-0.5f,0.0}},
        {{0.5f,-0.5f,0.0}},
        {{-0.5f,0.5f,0.0}},
    };
    
    //4.生成緩存,併爲緩存提供數據
    glGenBuffers(1, &_vertexBufferID);//申請一個標識符
    glBindBuffer(GL_ARRAY_BUFFER, _vertexBufferID);//將標識符綁定到GL_ARRAY_BUFFER
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);//複製定點數據從CPU 到 GPU
    
    //5.代理方法
    
    //6.dealloc 中,釋放緩存數據
    
}

//系統給咱們回調的繪製消息，該方法會一直被調用，和display方法一致
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect{
    [self.baseEffect prepareToDraw];
    
    //clear Frame buffer
    glClear(GL_COLOR_BUFFER_BIT);
    //開啓對應的定點緩存屬性
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    //設置緩存數據指針,從頂點數組中讀取數據
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(sceneVertex), NULL);
    //繪圖
    glDrawArrays(GL_TRIANGLES, 0, 3);
    
    
    
}

- (void)dealloc{
    GLKView *view = (GLKView *)self.view;
    [EAGLContext setCurrentContext:view.context];
    if (_vertexBufferID != 0) {
        glDeleteBuffers(1, &_vertexBufferID);
        _vertexBufferID = 0;
    }
    
    
}

最終效果: