12 errors with open gl I've made

[Anonymous Username]

A while back I bought Iphone game development for dummies without reading reviews for it, apparently its crap. I wrote the code they used in the book and added everything to the header file so that's not the problem. I'm getting errors like

"_glGenFramebuffers", referenced from:
-[OpenGL prepareOpenGl] in OpenGl.o
symbol(s) not found

thats one of the twelve, all the errors end with "referenced" from.

heres the full code.

Opengl.h

#import <UIKit/UIKit.h>
#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/es2/glext.h>
#import <QuartzCore/QuartzCore.h>
#import <CoreGraphics/CoreGraphics.h>

@interface OpenGl : UIView {
	EAGLContext* context;
	
	GLuint framebuffer;
	
	GLuint colorRenderBuffer;
	
	GLuint depthBuffer;
}

Opengl.m

 #import "OpenGl.h"


@implementation OpenGl

- (void) prepareOpenGL {
	context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
	[EAGLContext setCurrentContext:context];

	glGenFramebuffers(1, &framebuffer);
	
	glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
	
	glGenRenderbuffers(1, &colorRenderBuffer);
	
	glBindRenderbuffer(GL_RENDERBUFFER, colorRenderBuffer);
	
	[context renderbufferStorage:GL_RENDERBUFFER fromDrawable: (CAEAGLLayer*) self.layer];
	
	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, colorRenderBuffer);

	GLint height, width;
	glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &width);
	glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &height);
	
	glGenRenderbuffers(1, &depthBuffer);
	glBindRenderbuffer(GL_RENDERBUFFER, depthBuffer);
	
	glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, width, height);
	
	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthBuffer);
	
	GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
	
	if (status != GL_FRAMEBUFFER_COMPLETE) {
		NSLog (@"failed to create a complete render buffer!");
	
}	
}

	- (void) awakeFromNib {
	[self prepareOpenGL];
	[self render];
}

	-(void) render { 
		glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
		
		glViewport(0, 0, self.bounds.size.width, self.bounds.size.height);
		
		glClearColor(0.5, 0.0, 0.0, 1.0);
		glClear(GL_COLOR_BUFFER_BIT) ;
		
		glBindRenderbuffer(GL_RENDERBUFFER, colorRenderBuffer);
		[context presentRenderbuffer:GL_RENDERBUFFER];
}



@end

I really don't know what I'm doing here :/

[mer10]

Originally Posted by Anonymous Username

A while back I bought Iphone game development for dummies without reading reviews for it, apparently its crap. I wrote the code they used in the book and added everything to the header file so that's not the problem. I'm getting errors like

"_glGenFramebuffers", referenced from:
-[OpenGL prepareOpenGl] in OpenGl.o
symbol(s) not found

thats one of the twelve, all the errors end with "referenced" from.

heres the full code.

Opengl.h

#import <UIKit/UIKit.h>
#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/es2/glext.h>
#import <QuartzCore/QuartzCore.h>
#import <CoreGraphics/CoreGraphics.h>

@interface OpenGl : UIView {
	EAGLContext* context;
	
	GLuint framebuffer;
	
	GLuint colorRenderBuffer;
	
	GLuint depthBuffer;
}

Opengl.m

 #import "OpenGl.h"


@implementation OpenGl

- (void) prepareOpenGL {
	context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
	[EAGLContext setCurrentContext:context];

	glGenFramebuffers(1, &framebuffer);
	
	glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
	
	glGenRenderbuffers(1, &colorRenderBuffer);
	
	glBindRenderbuffer(GL_RENDERBUFFER, colorRenderBuffer);
	
	[context renderbufferStorage:GL_RENDERBUFFER fromDrawable: (CAEAGLLayer*) self.layer];
	
	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, colorRenderBuffer);

	GLint height, width;
	glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &width);
	glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &height);
	
	glGenRenderbuffers(1, &depthBuffer);
	glBindRenderbuffer(GL_RENDERBUFFER, depthBuffer);
	
	glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, width, height);
	
	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthBuffer);
	
	GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
	
	if (status != GL_FRAMEBUFFER_COMPLETE) {
		NSLog (@"failed to create a complete render buffer!");
	
}	
}

	- (void) awakeFromNib {
	[self prepareOpenGL];
	[self render];
}

	-(void) render { 
		glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
		
		glViewport(0, 0, self.bounds.size.width, self.bounds.size.height);
		
		glClearColor(0.5, 0.0, 0.0, 1.0);
		glClear(GL_COLOR_BUFFER_BIT) ;
		
		glBindRenderbuffer(GL_RENDERBUFFER, colorRenderBuffer);
		[context presentRenderbuffer:GL_RENDERBUFFER];
}



@end

I really don't know what I'm doing here :/

Do you have xcode 4.2? I'd recommend starting a new OpenGL Game project if you do as it will lay out all the basic code framework you have there and provide you a decent starting place.

[Naughty_Ottsel]

May seem a bit silly but have you added the OpenGL framework to the project. Easily forgotten and can cause a lot of issues and errors.