Frame Buffer OpenGL

Hi !

 

For a project, I need to render some part of my scene in 2 opengl frame buffer, and to merge them by depth buffer comparison.

 

So I tried to split this problem in 2 tasks:

1. First:
1. Render a part of the scene into a framebuffer
2. Switch this framebuffer with the backbuffer
3. Switch the back buffer with the framefuffer
2. Second:
1. Merge the 2 framebuffer

 

 

I implemented the first part:

 

************FBO SETUP PART ********

 

// Create 2 render buffer

int [] MyRenderBuffer = newint[2];

glGenRenderbuffersEXT(2, MyRenderBuffer);

 

// Bind the first render buffer

glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, MyRenderBuffer[0]);

// Allocate memory for its: colorimetry buffer

glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT,GL_RGBA, CV.width, CV.height);

 

// Bind the first render buffer

glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, MyRenderBuffer[1]);

// Allocate memory for its: depth buffer

glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, CV.width, CV.height);

 

// Create a Frame Buffer Object & bind it

int [] MyFBO = newint[1];

glGenFramebuffersEXT(1, MyFBO);

glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFBO[0]);

 

// Attach the fist render buffer with the FBO "COLOR_ATTACHMENT0"

glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,GL_RENDERBUFFER_EXT, MyRenderBuffer[0]);

// Attach the fist render buffer with the FBO "DEPTH _ATTACHMENT0"

glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT,GL_DEPTH_ATTACHMENT_EXT,GL_RENDERBUFFER_EXT, MyRenderBuffer[1]);

 

// Bind the OpenGL Standard framebuffer

glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

 

// Check FBO Status

int status_fbo =glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);

int normal_status =GL_FRAMEBUFFER_COMPLETE_EXT;

 

 

 

 

 

************DRAW ********

// Bind the FBO

glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);

 

// Draw my scene

Draw();

 

// Re bind the OpenGL Standard framebuffer

glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

 

 

// Then SDL swaps buffers.

 

 

Results:

• My status_fbo is equal to "GL_FRAMEBUFFER_COMPLETE_EXT" ! (good)
• If I disable the line "glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);"  in the "Draw part", my scene is correctly shown on the screen. (good)
• If I enable line "glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);"  in the "Draw part", nothing is shown (no good)

 

Question:

Please, is anyone could help me to identify the mistake? I think I don't really switch the back buffer with my FBO, but I don't know why...