Window turns black in OpenGL - ios

Question

Hi I'm very new to ios and OpenGL. I'm trying to follow the instructions from the book iPhone 3d programming. I just want to render a grey screen from OpenGL.
I really don't know what I've done wrong, and I need to understand why I don't get my OpenGL window right before I can venture forth.
If I can help any further just post a comment :)
GLView.h:
#import <UIKit/UIKit.h>
#import <OpenGLES/EAGL.h>
#import <QuartzCore/QuartzCore.h>
#import <OpenGLES/ES1/gl.h>
#import <OpenGLES/ES1/glext.h>
#interface GLView : UIView {
// Protected fields
EAGLContext* m_context;
}
// public fields
-(void)drawWiew;
#end
GLView.mm:
#import "GLView.h"
#implementation GLView
+(Class) layerClass {
return [CAEAGLLayer class];
}
- (id)initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame:frame]) {
CAEAGLLayer* eaglLayer = (CAEAGLLayer*) super.layer;
eaglLayer.opaque = YES;
m_context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1];
if (!m_context || ![EAGLContext setCurrentContext:m_context]) {
[self release];
return nil;
}
// Initialization code
GLuint framebuffer, renderbuffer;
glGenFramebuffersOES(1, &framebuffer);
glGenRenderbuffersOES(1, &renderbuffer);
glBindFramebufferOES(GL_FRAMEBUFFER_OES, framebuffer);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, renderbuffer);
[m_context
renderbufferStorage:GL_RENDERBUFFER_OES
fromDrawable:eaglLayer];
glFramebufferRenderbufferOES(
GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES,
GL_RENDERBUFFER_OES, renderbuffer);
glViewport(0, 0, CGRectGetWidth(frame), CGRectGetHeight(frame));
[self drawWiew];
}
return self;
}
-(void)drawWiew {
glClearColor(0.5f, 0.5f, 0.5f, 1);
glClear(GL_COLOR_BUFFER_BIT);
[m_context presentRenderbuffer:GL_RENDERBUFFER_OES];
NSLog(#"drawView called");
}
-(void)dealloc {
if ([EAGLContext currentContext] == m_context)
[EAGLContext setCurrentContext:nil];
[m_context release];
[super dealloc];
}
/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
// Drawing code
}
*/
#end
HellowArrowAppDelegate.h:
#import <UIKit/UIKit.h>
#import "GLView.h"
#interface HelloArrowAppDelegate : UIResponder <UIApplicationDelegate> {
UIWindow* window;
GLView* view;
}
#property (strong, nonatomic) UIWindow *window;
#end
HellowArrowAppDelegate.mm:
#import "HelloArrowAppDelegate.h"
#implementation HelloArrowAppDelegate
#synthesize window = _window;
- (void)dealloc
{
[_window release];
[super dealloc];
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
CGRect screenBounds = [[UIScreen mainScreen] bounds];
_window = [[UIWindow alloc] initWithFrame:screenBounds];
view = [[GLView alloc] initWithFrame:screenBounds];
[_window addSubview:view];
[_window makeKeyWindow];
// self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
// // Override point for customization after application launch.
// self.window.backgroundColor = [UIColor whiteColor];
// [self.window makeKeyAndVisible];
return YES;
}
- (void)applicationWillResignActive:(UIApplication *)application
{
/*
Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
*/
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
/*
Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
*/
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
/*
Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
*/
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
/*
Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
*/
}
- (void)applicationWillTerminate:(UIApplication *)application
{
/*
Called when the application is about to terminate.
Save data if appropriate.
See also applicationDidEnterBackground:.
*/
}
#end

Answer 1

OpenGL screens can turn black depending upon the version of the OS used, as well as the size of the screen window being drawn into. For instance, code that runs fine on 4.0, 4.1, and 4.3 can show up black in 4.2. Or if you double the size of the OpenGL window it works. Sometimes the firmware gets in the way--try messing around with using a newer version of the OS, and see if it works better.