iOS OpenGL ES載入紋理（GLKit）

1、準備工作

• 建立UIViewController檔案並繼承GLKViewController
• 遵守協議GLKViewDelegate
• 實現協議方法**- (void)glkView:(GLKView )view drawInRect:(CGRect)rect*
• 定義屬性：*@property (nonatomic,strong) GLKBaseEffect mEffect;

2、初始化上下文物件和被繪製物件引數的設定

- (void)setUpContext{
//初始化上下文物件
    EAGLContext *context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
    if(!context){
        NSLog(@"fail to create ES context");
    }
    //被繪製物件引數的設定
    GLKView *view = (GLKView *)self.view;
    view.context = context;
    //顏色格式：RGBA每個顏色通道站8位
    view.drawableColorFormat = GLKViewDrawableColorFormatRGBA8888;
    //深度格式：24位精度
    view.drawableDepthFormat = GLKViewDrawableDepthFormat24;
    //設定當前上下文
    [EAGLContext setCurrentContext:context];
    //開啟深度測試
    glEnable(GL_DEPTH_TEST);
    //清理螢幕（相當於設定螢幕顏色）
    glClearColor(1.0, 0.4, 0.3, 1.0);
}

3、設定頂點

- (void)setVertex{
    //頂點資料
    GLfloat vertexs[] = {
        -0.5,0.5,0.0, 0.0,1.0,//左上 + 紋理做點
        0.5,0.5,0.0,  1.0,1.0,//右上 + 紋理做點
        -0.5,-0.5,0.0,0.0,0.0,//左下 + 紋理做點
        
        0.5,0.5,0.0,  1.0,1.0,//右上 + 紋理做點
        0.5,-0.5,0.0, 1.0,0.0,//右下 + 紋理做點
        -0.5,-0.5,0.0,0.0,0.0//左下 + 紋理做點
    };
    
    //開闢緩衝區
    GLuint buffer;
    glGenBuffers(1, &buffer);
    glBindBuffer(GL_ARRAY_BUFFER, buffer);
    //將頂點資料拷貝至緩衝區（相當於將頂點資料從cpu轉到gpu）
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertexs), vertexs, GL_STATIC_DRAW);

    //開啟位置屬性並賦值至頂點著色器的位置屬性（GLKVertexAttribPosition）
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 5, (GLfloat *)NULL+0);
    
    //開啟紋理座標屬性並賦值至頂點著色器的紋理屬性（GLKVertexAttribTexCoord0）
    glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
    glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 5, (GLfloat *)NULL+3);
}

4、載入紋理

- (void)loadTexture{
    //獲取圖片路徑
    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"cTest" ofType:@"jpg"];
    //紋理顯示屬性設定
    NSDictionary *option = [NSDictionary dictionaryWithObjectsAndKeys:@(1),GLKTextureLoaderOriginBottomLeft, nil];
    //載入紋理資訊
    GLKTextureInfo *textureInfo = [GLKTextureLoader textureWithContentsOfFile:filePath options:option error:nil];
    GLKBaseEffect *mEffect = [[GLKBaseEffect alloc] init];
    mEffect.texture2d0.enabled = GL_TRUE;
    mEffect.texture2d0.name = textureInfo.name;
    self.mEffect = mEffect;
}

5、遵守協議GLKViewDelegate

- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect{
    //螢幕顯示紋理
    glClearColor(0.3, 0.6, 1.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    [self.mEffect prepareToDraw];
    glDrawArrays(GL_TRIANGLES, 0, 6);
}

6、效果

• 有空會繼續更新使用GLSL方式載入紋理
• 如有錯誤理解，還請各路大神批評指出
• 轉載請標明出處