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Forum Topic - FBO flushing: (10 Items)

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Brian Edmond(deleted)

05/06/2012 12:33 PM

post92925

I am using QNX 6.5 on a Beagleboard (PowerVR) and see issues when using a FBO as a scratch buffer.  I have this senerio:


Main Window Surface
  Create a FBO to render to (FBO1)
    Create a second FBO to render to (FBO2)
       Render content1 to FBO2
    Render FBO2 to FBO1 as a texture
       Clear and Render content2 to FBO2
    Render FBO2 to FBO1 as a texture
  Render FBO1 to Window surface as a texture
SwapBuffers

What I see is that only "content2" is visible.  It seems that if I reuse the same FBO in a render cycle that the last 
thing I rendered gets displayed.  This is true even if I call glFlush or glFinish after I render the FBO texture.

Is there something in the driver which does not execute the texture operations until the flush or should this work?

Brian

Joel Pilon(deleted)

05/06/2012 12:47 PM

post92926

Re: FBO flushing

This is fixed in newer drivers, the work around is to use more fbos.

----- Original Message -----
From: Brian Edmond [mailto:community-noreply@qnx.com]
Sent: Sunday, May 06, 2012 12:33 PM
To: opengles-graphics <opengles-graphics@community.qnx.com>
Subject: FBO flushing

I am using QNX 6.5 on a Beagleboard (PowerVR) and see issues when using a FBO as a scratch buffer.  I have this senerio:

Main Window Surface
  Create a FBO to render to (FBO1)
    Create a second FBO to render to (FBO2)
       Render content1 to FBO2
    Render FBO2 to FBO1 as a texture
       Clear and Render content2 to FBO2
    Render FBO2 to FBO1 as a texture
  Render FBO1 to Window surface as a texture
SwapBuffers

What I see is that only "content2" is visible.  It seems that if I reuse the same FBO in a render cycle that the last 
thing I rendered gets displayed.  This is true even if I call glFlush or glFinish after I render the FBO texture.

Is there something in the driver which does not execute the texture operations until the flush or should this work?

Brian

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Brian Edmond(deleted)

05/06/2012 1:25 PM

post92927

Re: FBO flushing

Can you point me to a patch which addresses this?  I would like to check the version of my driver as it was provided by 
a customer.

I tried using more FBO's but I ran into another issue.  If I do the following:

Create FBO to render to
  Create FBO
    render content to FBO
  Render FBO as a texture
  Release FBO  
  Create FBO
    render content to FBO
  Render FBO as a texture
  Release FBO
  -- and so on many  times
Swap Buffers

I will eveentually run out of memory, or crash in a glClear (I assume out of memory as the system is low).  I assume the
 Release of the FBO is not freeing the memory because it is referenced somewhere and not released until the SwapBuffers?


Brian

Joel Pilon(deleted)

05/06/2012 4:28 PM

post92928

Re: FBO flushing

I'm not aware of the omap bsp roadmap. Someone else will have to comment.

----- Original Message -----
From: Brian Edmond [mailto:community-noreply@qnx.com]
Sent: Sunday, May 06, 2012 01:25 PM
To: opengles-graphics <opengles-graphics@community.qnx.com>
Subject: Re: FBO flushing

Can you point me to a patch which addresses this?  I would like to check the version of my driver as it was provided by 
a customer.

I tried using more FBO's but I ran into another issue.  If I do the following:

Create FBO to render to
  Create FBO
    render content to FBO
  Render FBO as a texture
  Release FBO  
  Create FBO
    render content to FBO
  Render FBO as a texture
  Release FBO
  -- and so on many  times
Swap Buffers

I will eveentually run out of memory, or crash in a glClear (I assume out of memory as the system is low).  I assume the
 Release of the FBO is not freeing the memory because it is referenced somewhere and not released until the SwapBuffers?

Brian

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http://community.qnx.com/sf/go/post92927
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Brian Edmond(deleted)

05/08/2012 9:52 AM

post92929

Re: FBO flushing

So do you know if that was ever released?  Or when the fix was done?

Also any comment on my other question about releasing the memory, is that a known issue also?

Joel Pilon(deleted)

05/08/2012 2:48 PM

post92930

Re: FBO flushing

I'm not sure what's been released or to who. You would need a 1.7 driver. The egl strings tell you which major version 
of the driver you're using.

However note the fix is to ghost (make addition copies) of render buffers. So if you were running out of memory using 
additional fbos, its quite likely you'll have the same issue with the newer driver. This kind of rendering really 
doesn't play well with deferred rendering tile based architectures. 

-Joel


----- Original Message -----
From: Brian Edmond [mailto:community-noreply@qnx.com]
Sent: Tuesday, May 08, 2012 09:52 AM
To: opengles-graphics <opengles-graphics@community.qnx.com>
Subject: Re: FBO flushing

So do you know if that was ever released?  Or when the fix was done?

Also any comment on my other question about releasing the memory, is that a known issue also?




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Chris Keating(deleted)

05/19/2012 7:03 PM

post93219

Re: FBO flushing

To workaround this at the application level, do I just create extra render-buffers/textures?  Do I need to render the 
same content to the extra render-buffer/FBO? Or can I do something like this:

Create FBO-A
Create FBO-B (create 2 textures of dim. WxH, call glFrameBufferTexture2d on both)
Draw FBO-B to FBO-A

Joel Pilon(deleted)

05/19/2012 7:53 PM

post93220

Re: FBO flushing

That's should be fine. Just don't render to a texture and use it again to render to fbo0 or another texture.

----- Original Message -----
From: Chris Keating [mailto:community-noreply@qnx.com]
Sent: Saturday, May 19, 2012 07:03 PM
To: opengles-graphics <opengles-graphics@community.qnx.com>
Subject: Re: FBO flushing

To workaround this at the application level, do I just create extra render-buffers/textures?  Do I need to render the 
same content to the extra render-buffer/FBO? Or can I do something like this:

Create FBO-A
Create FBO-B (create 2 textures of dim. WxH, call glFrameBufferTexture2d on both)
Draw FBO-B to FBO-A

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Chris Keating(deleted)

05/19/2012 8:20 PM

post93221

Re: FBO flushing

That's what I need to do though -- render to an offscreen, which gets rendered to another offscreen?  How can this be 
accomplished without upgrading the driver?

Joel Pilon(deleted)

05/19/2012 9:55 PM

post93222

Re: FBO flushing

That should be fine, just don't re-use the same object in multiple renders in the same frame.

----- Original Message -----
From: Chris Keating [mailto:community-noreply@qnx.com]
Sent: Saturday, May 19, 2012 08:20 PM
To: opengles-graphics <opengles-graphics@community.qnx.com>
Subject: Re: FBO flushing

That's what I need to do though -- render to an offscreen, which gets rendered to another offscreen?  How can this be 
accomplished without upgrading the driver?

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OpenGL ES
http://community.qnx.com/sf/go/post93221
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