iOS OpenGL ES加载纹理（GLKit）

1、准备工作

• 创建UIViewController文件并继承GLKViewController
• 遵守协议GLKViewDelegate
• 实现协议方法*- (void)glkView:(GLKView )view drawInRect:(CGRect)rect
• 定义属性：*@property (nonatomic,strong) GLKBaseEffect mEffect;

2、初始化上下文对象和被绘制对象参数的设置

- (void)setUpContext{
//初始化上下文对象
    EAGLContext *context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
    if(!context){
        NSLog(@"fail to create ES context");
    }
    //被绘制对象参数的设置
    GLKView *view = (GLKView *)self.view;
    view.context = context;
    //颜色格式：RGBA每个颜色通道站8位
    view.drawableColorFormat = GLKViewDrawableColorFormatRGBA8888;
    //深度格式：24位精度
    view.drawableDepthFormat = GLKViewDrawableDepthFormat24;
    //设置当前上下文
    [EAGLContext setCurrentContext:context];
    //开启深度测试
    glEnable(GL_DEPTH_TEST);
    //清理屏幕（相当于设置屏幕颜色）
    glClearColor(1.0, 0.4, 0.3, 1.0);
}

3、设置顶点

- (void)setVertex{
    //顶点数据
    GLfloat vertexs[] = {
        -0.5,0.5,0.0, 0.0,1.0,//左上 + 纹理做点
        0.5,0.5,0.0,  1.0,1.0,//右上 + 纹理做点
        -0.5,-0.5,0.0,0.0,0.0,//左下 + 纹理做点
        
        0.5,0.5,0.0,  1.0,1.0,//右上 + 纹理做点
        0.5,-0.5,0.0, 1.0,0.0,//右下 + 纹理做点
        -0.5,-0.5,0.0,0.0,0.0//左下 + 纹理做点
    };
    
    //开辟缓冲区
    GLuint buffer;
    glGenBuffers(1, &buffer);
    glBindBuffer(GL_ARRAY_BUFFER, buffer);
    //将顶点数据拷贝至缓冲区（相当于将顶点数据从cpu转到gpu）
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertexs), vertexs, GL_STATIC_DRAW);

    //开启位置属性并赋值至顶点着色器的位置属性（GLKVertexAttribPosition）
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 5, (GLfloat *)NULL+0);
    
    //开启纹理坐标属性并赋值至顶点着色器的纹理属性（GLKVertexAttribTexCoord0）
    glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
    glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 5, (GLfloat *)NULL+3);
}

4、加载纹理

- (void)loadTexture{
    //获取图片路径
    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"cTest" ofType:@"jpg"];
    //纹理显示属性设置
    NSDictionary *option = [NSDictionary dictionaryWithObjectsAndKeys:@(1),GLKTextureLoaderOriginBottomLeft, nil];
    //加载纹理信息
    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、遵守协议GLKViewDelegate

- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect{
    //屏幕显示纹理
    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

• 有空会继续更新使用GLSL方式加载纹理
• 如有错误理解，还请各路大神批评指出
• 转载请标明出处