Ios OpenGL视图仅显示空（粉红色）屏幕

我将在opengl视图上显示像素数据。 但我什么也看不见，只能看到那空的粉红色屏幕。 请检查我的代码，让我知道有什么问题

@implementation GLView
+ (Class) layerClass 
{
    return [CAEAGLLayer class];
}

- (id)initWithFrame:(CGRect)frame 
{
    if ((self = [super initWithFrame:frame])) 
    {
        // Do OpenGL Core Animation layer setup
        CAEAGLLayer *eaglLayer = (CAEAGLLayer *)self.layer;
        eaglLayer.opaque = YES;
        eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:NO], kEAGLDrawablePropertyRetainedBacking, kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat, nil];        
        context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];

        if (!context || ![EAGLContext setCurrentContext:context]
                || ![self createFramebuffers])
            return nil;
    }
    return self;
}

- (BOOL)createFramebuffers
{   
    glEnable(GL_TEXTURE_2D);
    glDisable(GL_DEPTH_TEST);

    // Onscreen framebuffer object
    glGenFramebuffers(1, &viewFramebuffer);
    glBindFramebuffer(GL_FRAMEBUFFER, viewFramebuffer);

    glGenRenderbuffers(1, &viewRenderbuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer);

    [context renderbufferStorage:GL_RENDERBUFFER fromDrawable:(CAEAGLLayer*)self.layer];

    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &backingWidth);
    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &backingHeight);
    NSLog(@"Backing width: %d, height: %d", backingWidth, backingHeight);

    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, viewRenderbuffer);

    if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) 
    {
        NSLog(@"Failure with framebuffer generation");
        return NO;
    }

    return YES;
}

- (void)setDisplayFramebuffer;
{
    if (context)
    {
//        [EAGLContext setCurrentContext:context];
        if (!viewFramebuffer)
            [self createFramebuffers];
        glBindFramebuffer(GL_FRAMEBUFFER, viewFramebuffer);
//        glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer);
        glViewport(0, 0, backingWidth, backingHeight);
    }
}

- (BOOL)presentFramebuffer;
{
    BOOL success = FALSE;
    if (context)
    {
  //      [EAGLContext setCurrentContext:context];
        glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer);
        success = [context presentRenderbuffer:GL_RENDERBUFFER];
    }
    return success;
}

和在viewcontroller中

m_glView = [[GLView alloc] initWithFrame:CGRectMake(0, 0, m_viewPlayer.frame.size.width, m_viewPlayer.frame.size.height)];
[m_viewPlayer addSubview:m_glView];
[self loadVertexShader:@"DirectDisplayShader" fragmentShader:@"DirectDisplayShader" forProgram:&m_directDisplayProgram];

和在定时器循环中

CMSampleBufferRef buf = [m_trackOutput copyNextSampleBuffer];
if (buf == nil)
    return;

[self processFrame:buf]; // draw frame to opengl view
CFRelease(buf);


- (void)processFrame:(CMSampleBufferRef)sampleBuffer
{
    if (m_videoFrameTexture)
        glDeleteTextures(1, &m_videoFrameTexture);

    // Get a CMSampleBuffer's Core Video image buffer for the media data
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    // Lock the base address of the pixel buffer
    CVPixelBufferLockBaseAddress(imageBuffer, 0);

    CGFloat width = CVPixelBufferGetWidth(imageBuffer);
    CGFloat height = CVPixelBufferGetHeight(imageBuffer);

    // Create a new texture from the camera frame data, display that using the shaders
    glGenTextures(1, &m_videoFrameTexture);
    glBindTexture(GL_TEXTURE_2D, m_videoFrameTexture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    // This is necessary for non-power-of-two textures
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    // Using BGRA extension to pull in video frame data directly
//    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddress(imageBuffer));
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddress(imageBuffer));

    [self drawFrame];

//  glDeleteTextures(1, &videoFrameTexture);

    CVPixelBufferUnlockBaseAddress(imageBuffer, 0);
}

- (void)drawFrame
{
    [m_glView setDisplayFramebuffer];
    [self drawCapturedScreen];
    [m_glView presentFramebuffer];
}

- (void)drawCapturedScreen
{
    glUseProgram(m_directDisplayProgram);
    glBindTexture(GL_TEXTURE_2D, m_videoFrameTexture);
    glUniform1i(uniforms[UNIFORM_VIDEOFRAME], 0);

    // Update attribute values.
    static const GLfloat squareVertices[] = {
        -1.0f, -1.0f,
        1.0f, -1.0f,
        -1.0f,  1.0f,
        1.0f,  1.0f,
    };
    glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, 0, 0, squareVertices);
    glEnableVertexAttribArray(ATTRIB_VERTEX);

    float m_fScale = 1.0f; //
    GLfloat kRate = 1.0f/m_fScale;
    GLfloat kX = (1.0-kRate)/2;
    GLfloat kY = (1.0-kRate)/2;
    GLfloat kS = kX+kRate;
    GLfloat kT = kY+kRate;
    {
        {
            GLfloat textureVertices[] = {
                kS, kT,
                kS, kY,
                kX, kT,
                kX, kY,
            };
            glVertexAttribPointer(ATTRIB_TEXTUREPOSITON, 2, GL_FLOAT, 0, 0, textureVertices);
            glEnableVertexAttribArray(ATTRIB_TEXTUREPOSITON);
        }
    }

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}

---

到目前为止，您是否已成功地在OpenGL中渲染了任何内容？我建议你把你正在做的事情分解成更小的步骤，先让它们工作起来。首先尝试使用GL_点进行渲染，看看是否可以得到任何东西，然后再从中构建。使着色器尽可能简单，以检查是否存在问题。您应该尝试使用最简单的渲染，然后增加复杂性（例如，在点之后尝试直线，然后尝试三角形，然后尝试纹理三角形）。通过分解渲染，您可以隔离导致draw调用不显示任何内容的原因。

请尝试使用glGetError（）从openGL添加一些错误处理。还有，为什么你会看到一个粉红色的屏幕？尝试清除一些特定的颜色，这样你至少可以看到你得到的。