OpenGL FBO (Step by step)

Step by step how to use EXT_framebuffer_object.

Check extenstion

1. - (BOOL) initFBO  
2. {  
3.     // check extension  
4.     const GLubyte* extensions = glGetString ( GL_EXTENSIONS );  
5.     if ( extensions )  
6.     {     
7.         if(gluCheckExtension((GLubyte*)("GL_EXT_framebuffer_object"), extensions))  
8.             return YES;  
9.     }  
10.     return NO;  
11. }  

сreate the texture for framebuffer

1. GLuint textureId      
2. glGenTextures ( 1, &textureId );  
3. glBindTexture ( GL_TEXTURE_2D, textureId );  
4. glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );  
5. glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );  
6. glTexImage2D ( GL_TEXTURE_2D, 0, 4, TextureWidth, TextureHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0 );  

сreate framebuffer (FBO)

1. GLuint frameBufferId;  
2.   
3. glGenFramebuffersEXT ( 1, &frameBufferId ); // 0 - main buffer, framebufferId > 0  
4. glBindFramebufferEXT ( GL_FRAMEBUFFER_EXT, frameBufferId );  
5. glFramebufferTexture2DEXT ( GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,  
6.  GL_TEXTURE_2D, textureId, 0 ); // attach texture to fbo  
7.   
8. // check fbo ( glCheckFramebufferStatusEXT )  
9. // ...  
10.   
11. glBindFramebufferEXT ( GL_FRAMEBUFFER_EXT, 0 ); // select main buffer  

сheck framebuffer

1. GLenum status = glCheckFramebufferStatusEXT ( GL_FRAMEBUFFER_EXT );  
2. if ( status != GL_FRAMEBUFFER_COMPLETE_EXT )  
3. {  
4.     switch ( status )  
5.     {  
6.         case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT:  
7.             NSLog(@"FrameBuffer Error - GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT");  
8.             break;  
9.         case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT:  
10.             NSLog(@"FrameBufferErGL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT");  
11.             break;  
12.         case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT:  
13.             NSLog(@"FrameBuffer Error - GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT");  
14.             break;  
15.         case GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT:  
16.             NSLog(@"FrameBuffer Error - GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT");  
17.             break;  
18.         case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT:  
19.             NSLog(@"FrameBuffer Error - GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT");                            
20.             break;  
21.         case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT:  
22.             NSLog(@"FrameBuffer Error - GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT");  
23.             break;  
24.         case GL_FRAMEBUFFER_UNSUPPORTED_EXT:  
25.             NSLog(@"FrameBuffer Error - GL_FRAMEBUFFER_UNSUPPORTED_EXT");  
26.             break;  
27.         default:  
28.             NSLog(@"FrameBuffer Error - Unknown error");  
29.               
30.             break;  
31.     }  
32.         
33.     return NO;  
34. }  

use in the code

1. glBindFramebufferEXT ( GL_FRAMEBUFFER_EXT, frameBufferId ); // select fbo
2.   
3. glClearColor ( 0.0f, 0.0f, 1.0f, 1.0f );   
4. glClear ( GL_COLOR_BUFFER_BIT );  
5.   
6. // render into texture ( update model view transforms )
7. // ...  
8.   
9. glBindFramebufferEXT ( GL_FRAMEBUFFER_EXT, 0 );      // select main buffer  

We can use the texture for post-effects. Do not forget to delete resources ;-)

Example OpenGL FBO (github) 

ePic for Mac 1.4 (winter release)

What's New in Version 1.4


* Full support for OS X Lion, including full-screen mode
* Improved support multi-touch gestures to Magic Trackpad and Magic Mouse
* Support Aperture libraries
* Support Picasa web albums
* Support iPhoto albums
* New mode for 3D presentation ( Breath presentation )
* New SlideShow effects ( two nice effect's )
* Ability to hide the control panel
* Function detailed view your photos in a Slide Show
* Many minor fixes

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