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Framebuffer depth test with depth and stencil buffer


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#1 moldyviolinist   Members   -  Reputation: 192

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Posted 29 July 2013 - 11:45 AM

I'm attempting to implement deferred shading. I've got a number of problems with it, but first and foremost, depth testing is not working right.

 

In my deferred shading, I create a depth buffer, naturally. Depth testing works fine with this. But if I create a depth and stencil buffer, depth testing just doesn't work. It's peculiar.

 

Buffer creation, depth component only, depth testing works:

 

glBindTexture(GL_TEXTURE_2D, depth_map);
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT32F, width, height, 0, GL_DEPTH_COMPONENT, GL_FLOAT, NULL);
glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, depth_map, 0);
 
Buffer creation, depth and stencil components, depth testing doesn't work:
 
glBindTexture(GL_TEXTURE_2D, depth_map);
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH32F_STENCIL8, width, height, 0, GL_DEPTH_STENCIL, GL_FLOAT, NULL);
glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_TEXTURE_2D, depth_map, 0);
 
This is literally the only change to my code, and depth testing works for the first one, and fails for the second one. Stencil test is disabled, depth test enabled for both. Any suggestions to fix this problem? I found a thread several years old, but only somewhat related, suggesting this was an AMD driver problem, and indeed I have an AMD card. Hopefully I'm just doing something wrong.
 
Thanks.

Edited by moldyviolinist, 29 July 2013 - 11:46 AM.


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#2 NumberXaero   Prime Members   -  Reputation: 1515

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Posted 29 July 2013 - 03:43 PM

Ive had problems myself with the depth stencil format on AMD within the last year or so, so I wouldnt rule that out. Not sure if any of their drivers ever got it right. I was using the depth24 stencil8. Not sure which version of opengl you are targeting, but you might try binding the depth_stencil texture to both the depth attachment and stencil attachment.

glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, tex_depthstencil, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_TEXTURE_2D, tex_depthstencil, 0);

Extension ARB_depth_buffer_float provides DEPTH32F_STENCIL which requires extension EXT_packed_depth_stencil, see use example at bottom of page

 

http://www.opengl.org/registry/specs/EXT/packed_depth_stencil.txt

 

see if that helps


Edited by NumberXaero, 29 July 2013 - 03:44 PM.


#3 moldyviolinist   Members   -  Reputation: 192

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Posted 29 July 2013 - 04:10 PM

Thanks for your suggestions. I tried switching to depth24 stencil 8, but that didn't change anything. I also tried switching to binding the texture to both attachments, but that also didn't make any changes. I'll have to keep trying things.

 

Is there a way to just create and bind depth and stencil completely separately? That way I can use the stencil-less depth to correctly depth test, and still use the stencil buffer for deferred shading. 



#4 moldyviolinist   Members   -  Reputation: 192

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Posted 29 July 2013 - 04:50 PM

glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH24_STENCIL8, m_width, m_height, 0, GL_DEPTH_STENCIL, GL_UNSIGNED_INT_24_8, NULL);

This actually fixes the depth test problems, but somehow introduces buffer clearing issues. I'm not sure how that's possible, since everything was clearing fine before.


Edited by moldyviolinist, 29 July 2013 - 04:53 PM.


#5 moldyviolinist   Members   -  Reputation: 192

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Posted 29 July 2013 - 08:13 PM

OK, well it looks like I solved it. 

 

It seem that the order of operations of glClear() and glDepthMask(GL_TRUE) actually really matters. Depth mask needs to be true BEFORE you clear. It makes sense, because it allows writing the depth buffer. If it's false when you clear, you won't clear the depth buffer.

 

I was trying to have the depth mask true for my geometry pass, but false for light and stencil passes. Without realizing the implications I just put the depth mask true after the clear. 

 

Hopefully this will help anyone with a similar issue.

 

Mods can close the thread I guess?


Edited by moldyviolinist, 29 July 2013 - 08:13 PM.





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