• This project is 2D, but uses depth test.
• I've been trying so many things to make this work that the code is a mess of comments and unnecessary calls to OpenGL functions like gl.glEnable(GL_TEXTURE_2D); 

1. public static GL begin(PApplet app) {

   pgl = ((PGraphicsOpenGL) app.g).beginPGL();

   gl = pgl.gl.getGL().getGL2();

   Verbose.debug("This system uses OpenGL:"+gl.glGetString(GL.GL_VERSION));

   return gl;

   }

2. public static int createFBO(){
3. int[] array = new int[1];
4. gl.glGenFramebuffers(1, array, 0);
5. return array[0];
6. }
7. /**
8. * Bind fbo.
9. *
10. * @param fbo the fbo
11. */
12. public static void bindFBO(int fbo){
13. gl.glBindFramebuffer(GL.GL_FRAMEBUFFER, fbo);
14. }
15. /**
16. * Inits the fbo.
17. *
18. * @param w the w
19. * @param h the h
20. * @return the object[]
21. * @throws Exception the exception
22. */
23. public static Object[] initFBO(int w, int h) throws Exception{
24. //Now create a texture
25. int[] array = new int[1];
26. gl.glGenTextures(1,array,0);
27. int tex = array[0];
28. 
    
29. gl.glEnable(GL.GL_TEXTURE_2D);
30. gl.glBindTexture(GL.GL_TEXTURE_2D, tex);
31. 
    
32. gl.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MIN_FILTER,
33.                 GL.GL_NEAREST);
34. gl.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MAG_FILTER,
35.                 GL.GL_NEAREST);
36. gl.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_WRAP_S,
37.                 GL.GL_CLAMP_TO_EDGE);
38. gl.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_WRAP_T,
39.                 GL.GL_CLAMP_TO_EDGE);
40. gl.glTexImage2D(GL.GL_TEXTURE_2D, 0, GL.GL_RGBA, w, h,
41.             0, GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, null);
42. 
    
43. initTexture(GL.GL_TEXTURE_2D, GL.GL_RGBA, w, h); //same code as in Processing PGL class
44. gl.glBindTexture(GL.GL_TEXTURE_2D, 0);
45. 
    
46. //and attach it to the FBO
47. //first create a Frame Buffer Object
48. int fbo = createFBO();
49. bindFBO(fbo);
50.     //gl.glFramebufferTexture2DEXT(GL.GL_FRAMEBUFFER_EXT, GL.GL_COLOR_ATTACHMENT0_EXT, GL.GL_TEXTURE_2D, tex, 0);
51. gl.glFramebufferTexture2D(GL.GL_FRAMEBUFFER, GL.GL_COLOR_ATTACHMENT0, GL.GL_TEXTURE_2D, tex, 0);
52. //then create a render buffer
53. //gl.glGenRenderbuffersEXT(1, array,0);
54. gl.glGenRenderbuffers(1, array,0);
55. int rb = array[0];
56. gl.glBindRenderbuffer(GL.GL_RENDERBUFFER, rb);
57. //ask for a depth buffer and sets the size
58. gl.glRenderbufferStorage(GL.GL_RENDERBUFFER, GL2.GL_DEPTH_COMPONENT24, w, h);
59. //attach it
60. gl.glFramebufferRenderbuffer(GL2.GL_DRAW_FRAMEBUFFER, GL.GL_DEPTH_ATTACHMENT, GL.GL_RENDERBUFFER, rb);
61. 
    
62. 
    
63.    
64.     //check for completeness
65. if(!checkBufferCompletness()){
66. throw new Exception("Init FBO: rendering to texture could not be initialised.");
67. }
68. 
    
69.     gl.glBindFramebuffer(GL.GL_FRAMEBUFFER, 0);
70.     gl.glBindRenderbuffer(GL.GL_RENDERBUFFER, 0);
71.     disableTexture(0);
72.     return new Object[]{fbo,rb,new Texture(tex)};
73. }

However, when I bind this FBO to render to its attached texture, the completeness test fails and report a GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT, which seems to indicate that there is no texture attached to the FBO.

This is how I'm binding the FBO inside the sketch draw() method:

1. gl.glEnable(GL.GL_TEXTURE_2D);
2. // w and h are the dimension of the FBO, fbo is the id of fbo object created by the code above
3. gl.glBindFramebuffer(GL.GL_FRAMEBUFFER,fbo);
4. gl.glPushAttrib(GL2.GL_VIEWPORT_BIT); //save the current viewport info
5. gl.glViewport(0,0,w, h); //make sure we draw in a big enough area

I checked the PGL class source code and I can see that a few FBOs are also created there. Could there be some sort of conflict when using multiple FBOs?

I've tried more involved debugging technics without much luck either.

Even if I get this working, I'm not sure this is the most effective solution (see here). Any thoughts?

I'm far from being an OpenGL expert and I have very little understanding of how it is setup by Processing, so I'm open to any suggestion regarding a different way of achieving the same thing (take snapshots and save them to files, render at different scales in realtime, do high resolution rendering).

Thanks in advance and have a merry easter.