Can't seem to get to render using opengl es 1.1 on simulator

Question

I am a complete noob to OpenGL, I have been trying to get this simple piece of code to render on the iphone simulator, it starts up fine, the splash screen shows and then...nothing...just darkness, I can't tell what I am missing, can some please help? I haven't done anything for rotation yet, waiting to see what I have rendered first, then move on to rotation and such...

I am using Xcode 4.2, if that matters.

Here is my code:

IRenderEngine.cpp

#ifndef HelloArrow_IRenderingEngine_hpp
#define HelloArrow_IRenderingEngine_hpp

#import <OpenGLES/ES1/gl.h>
#import <OpenGLES/ES1/glext.h>

//Physical Orientation of a handheld device, equivalent to UIDeviceOrientation
enum DeviceOrientation{
DeviceOrientationUnknown,
DeviceOrientationPortrait,
DeviceOrientationPortraitUpsideDown,
DeviceOrientationLandscapeLeft,
DeviceOrientationLandscapeRight,
DeviceOrientationFaceUp,
DeviceOrientationFaceDown
};

//Creates an instance of a renderer and sets up various openGL state
struct IRenderingEngine *CreateRenderer1();

//Interface to OpenGL ES renderer; consumed by GLView
struct IRenderingEngine{
virtual void Initialize(int width, int height)=0;
virtual void Render() = 0;
virtual void UpdateAnimation(float timeStep) = 0;
virtual void OnRotate(DeviceOrientation newOrientation) = 0;
virtual ~IRenderingEngine(){};
};

RenderingEngine.cpp

#include <iostream>

#include <OpenGLES/ES1/gl.h>

#include <OpenGLES/ES1/glext.h>

#include "IRenderingEngine.hpp"


class RenderingEngine1 : public IRenderingEngine{
public:
RenderingEngine1();
void Initialize(int width, int height);
void Render();
void UpdateAnimation(float timeStep){}
void OnRotate(DeviceOrientation newOrientation){}
private:
GLuint m_framebuffer;
GLuint m_renderbuffer;
};

IRenderingEngine * CreateRenderer1(){
return new RenderingEngine1;
}

struct Vertex {
float Position[2];
float Color[4];
};

//Define the position and colors of the 2 triangles
const struct Vertex Vertices[6] = {
{{-0.5, -0.866},{1, 1, 0.5f, 1}},
{{0.5, -0.866},{1,1,0.5f,1}},
{{0,1},{1,1,0.5f,1}},
{{-0.5, -0.866},{0.5f,0.5f,0.5f}},
{{0.5, -0.866},{0.5f,0.5f,0.5f}},
{{0,-0.4f},{0.5f,0.5f,0.5f}}
};
RenderingEngine1::RenderingEngine1(){
glGenRenderbuffersOES(1, &m_renderbuffer);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, m_renderbuffer);
}

void RenderingEngine1::Initialize(int width, int height){
//Create the framebuffer object and attache the renderbuffer    
glGenFramebuffersOES(1, &m_framebuffer);
glBindFramebufferOES(GL_FRAMEBUFFER_OES, m_framebuffer);

glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES,     GL_RENDERBUFFER_OES, m_renderbuffer);

glViewport(0, 0, width, height);

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

const float maxX = 2;
const float maxY = 3;

glOrthof(-maxX,+maxX,-maxY,+maxY,-1,1);


glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

}

void RenderingEngine1::Render(){

glClearColor(0.5f, 0.5f, 0.5f, 1);


glClear(GL_COLOR_BUFFER_BIT);


glEnableClientState(GL_VERTEX_ARRAY);


glEnableClientState(GL_COLOR_ARRAY);
glVertexPointer(2,GL_FLOAT,4,&Vertices[0].Position);


glColorPointer(4,GL_FLOAT,2,&Vertices[0].Color);

GLsizei vertexcount = sizeof(Vertices)/sizeof(Vertex);
glDrawArrays(GL_TRIANGLES, 0, vertexcount);
glFlush();
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
}

GLView.h

#import "IRenderingEngine.hpp"
#import <UIKit/UIKit.h>
#import <OpenGLES/EAGL.h>
#import <QuartzCore/QuartzCore.h>


@interface GLView : UIView
{
EAGLContext *m_context;
struct IRenderingEngine *m_renderingEngine;
float m_timestamp;
}

-(void) drawView:(CADisplayLink*) displayLink;
-(void) didRotate: (NSNotification*) notification;

@end

GLView.mm

#import <OpenGLES/EAGLDrawable.h>
#import <OpenGLES/ES1/gl.h> //<- for GL_RENDERBUFFER only
#import "GLView.h"
#import "mach/mach_time.h"
#import "IRenderingEngine.hpp"

@implementation GLView

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

- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
    // Initialization code
    CAEAGLLayer *eaglLayer = (CAEAGLLayer*) super.layer;
    eaglLayer.opaque = YES;
    m_context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1];

    if(!m_context || ![EAGLContext setCurrentContext:m_context]){
        return nil;
    }

    m_renderingEngine = CreateRenderer1();    

    [m_context renderbufferStorage:GL_RENDERBUFFER fromDrawable:eaglLayer];

    m_renderingEngine->Initialize(CGRectGetWidth(frame), CGRectGetHeight(frame));
    [self drawView:nil];
    m_timestamp = CACurrentMediaTime();
    CADisplayLink *displayLink;
    displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(drawView:)];
    [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didRotate:) name:UIDeviceOrientationDidChangeNotification object:nil];

}
return self;
}

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
// Drawing code
}
*/

-(void) drawView: (CADisplayLink *) displayLink{

if(displayLink != nil){
    float elapsedseconds = [displayLink timestamp] - m_timestamp;
    m_timestamp = [displayLink timestamp];
    m_renderingEngine->UpdateAnimation(elapsedseconds);
}
m_renderingEngine->Render();

[m_context presentRenderbuffer:GL_RENDERBUFFER_OES];

}

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

-(void) didRotate:(NSNotification *)notification{
UIDeviceOrientation orientation = [[UIDevice currentDevice] orientation];
m_renderingEngine->OnRotate((DeviceOrientation) orientation);
[self drawView:nil];
}

@end

AppDelegate.h

#import <UIKit/UIKit.h>
#import "GLView.h"

@class ViewController;

@interface AppDelegate : UIResponder <UIApplicationDelegate>{
UIWindow *m_window;
GLView *m_view;
}

@property (strong, nonatomic) IBOutlet UIWindow *m_window;

@end

and, finally, AppDelegate.mm

#import "AppDelegate.h"
#import "OpenGLVC.h"
#import <UIKit/UIKit.h>

@implementation AppDelegate

@synthesize m_window = _window;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
CGRect screenBounds = [[UIScreen mainScreen] bounds];
self.m_window = [[UIWindow alloc] initWithFrame:screenBounds];
m_view = [[GLView alloc] initWithFrame:screenBounds];
[m_window addSubview:m_view];
[application setStatusBarHidden:YES withAnimation:UIStatusBarAnimationNone];
OpenGLVC *oglvc = [[OpenGLVC alloc] init];
self.m_window.rootViewController = oglvc;
// Override point for customization after application launch.
[self.m_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

Try changing

glVertexPointer(2,GL_FLOAT,4,&Vertices[0].Position);
glColorPointer(4,GL_FLOAT,2,&Vertices[0].Color);

to

glVertexPointer(2,GL_FLOAT,sizeof(Vertex),&Vertices[0].Position);
glColorPointer(4,GL_FLOAT,sizeof(Vertex),&Vertices[0].Color);

The third argument in those two functions should be the stride, ie, the difference in byte offset between, say, Vertices[0].Position and Vertices[1].Position.

In other words, if you were standing at Vertices[i].Position and took a single long stride to then stand at Vertices[i+1].Position, how long would your stride have to have been in bytes (not floats) . It is not the gap that you have to skip over to get from the end of Vertices[i].Position to the start of Vertices[i+1].Position.

Also, the stride is always expressed in bytes, not floats or ints.

See:

http://www.opengl.org/sdk/docs/man/xhtml/glVertexPointer.xml

http://www.opengl.org/sdk/docs/man/xhtml/glColorPointer.xml