Question

glGenFramebuffers doesn’t allocate framebuffer object! I can’t get this small program to work.

The code:

/* ----- AppDelegate.h ----- */
#import <UIKit/UIKit.h>

#import "GLView.h"

@interface AppDelegate : NSObject <UIApplicationDelegate>{
@private
    UIWindow *window;
    GLView *view;
}

@end

---

/* ----- AppDelegate.h ----- */

#import "AppDelegate.h"

@implementation AppDelegate

- (void)dealloc
{
    [view release];
    [window release];
    [super dealloc];
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    CGRect frame = [[UIScreen mainScreen] bounds];

    window = [[UIWindow alloc] initWithFrame:frame];
    view = [[GLView alloc] initWithFrame:frame];

    [window addSubview:view];
    [window makeKeyAndVisible];
    return YES;
}

@end

---

/* ----- GLView.h ----- */

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
#import <OpenGLES/EAGL.h>
#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/ES2/glext.h>

@interface GLView : UIView{
@private
    EAGLContext* context;
    GLuint color_render_buffer;
    GLuint depth_render_buffer;
    GLuint frame_buffer;
}

-(void)render:(CADisplayLink*)displayLink;

@end

---

/* ----- GLView.mm ----- */

#import "GLView.h"

@implementation GLView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        CAEAGLLayer* eaglLayer = (CAEAGLLayer*)self.layer;
        eaglLayer.opaque = YES;

        context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
        if(!context && ![EAGLContext setCurrentContext:context]){
            [self release];
            return nil;
        }

        int width = (int)frame.size.width;
        int height = (int)frame.size.height;

        glGenFramebuffers(1, &frame_buffer);
        glBindFramebuffer(GL_FRAMEBUFFER, frame_buffer);
        if(glIsFramebuffer(frame_buffer) == GL_FALSE){
            //NSLog(@"%i", frame_buffer);
            NSLog(@"frame_buffer is GL_FALSE!");
        }

        glGenRenderbuffers(1, &color_render_buffer);
        glBindRenderbuffer(GL_RENDERBUFFER, color_render_buffer);
        [context renderbufferStorage:GL_RENDERBUFFER fromDrawable:eaglLayer];

        if(glIsRenderbuffer(color_render_buffer) == GL_FALSE){
            NSLog(@"%i", color_render_buffer);
            NSLog(@"color_render_buffer is GL_FALSE");
        }

        glGenRenderbuffers(1, &depth_render_buffer);
        glBindRenderbuffer(GL_RENDERBUFFER, depth_render_buffer);
        glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, width, height);

        if(glIsRenderbuffer(depth_render_buffer) == GL_FALSE){
            NSLog(@"depth_render_buffer is GL_FALSE");
        }


        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, color_render_buffer);
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth_render_buffer);

        if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE){
#ifdef DEBUG_LOG
            NSLog(@"Framebuffer is not complete!");
            exit(1);
#endif
        }

        [[CADisplayLink displayLinkWithTarget:self selector:@selector(render:)] addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    }
    return self;
}

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

-(void)dealloc{
    if([EAGLContext currentContext] == context){
        [EAGLContext setCurrentContext:nil];
    }

    [context release];
    [super dealloc];
}

-(void)render:(CADisplayLink*)displayLink{
    /* Rendering */

    [context presentRenderbuffer:GL_RENDERBUFFER];
}

@end

I always get “frame_buffer is GL_FALSE!” printed to console… frame_buffer is always 0 (window-system default framebuffer)
Is there any settings that need to be added to plist? Or am I missing something?

Please help.

Answer 1

You never call setCurrentContext: when context != nil.
Change:

if(!context && ![EAGLContext setCurrentContext:context]){

To:

if(!context || ![EAGLContext setCurrentContext:context]){