Hi, I checked the osgscreencapture example (from 2.9.8). It seems to only work asynchronously if I use the --rgba flag (time for read pixels = 0.045694ms time for memcpy = 1.5924ms) which sets the pixel format to GL_BGRA. Any other combination and the read-back slows down quite significantly (time for read pixels = 8.7473ms time for memcpy = 1.2335ms).
My case is slightly different since I am trying to read-back from a FBO float texture instead of the framebuffer directly. I tried using GL_RGBA32F_ARB as internal format, GL_BGRA as source format, and GL_FLOAT as source type, ping-ponging between 2 PBOs and textures, and doing the read-back in the first camera but without success... Has anyone managed to read a texture asynchronously into a PBO and could suggest ideas ? cheers, guillaume -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of J.P. Delport Sent: October-20-11 12:54 AM To: Poirier, Guillaume Cc: osg users Subject: Re: [osg-users] OSG question on asynchronous texture readback Hi, the GPURegionOfInterestCallback does not do async read at the moment, but you can have a look at the osgscreencapture example. Specifically check the code path for the --double-pbo command line option. Also see this page, it has the best explanation of async pbo I've come across. http://www.songho.ca/opengl/gl_pbo.html Getting data from GPU to CPU is still a bottleneck for many apps, make sure you send back as little as possible. cheers jp On 19/10/2011 19:13, Poirier, Guillaume wrote: > Hello J-P, > > I saw on the OSG forum archives your GPURegionOfInterestCallback code. > Can it provide asynchronous GPU -> CPU readback ? > > I don't know much about PBO and I currently does the readback by simply > attaching an image to my RTT camera, however it > > slows down the application significantly. Can you show an example of how > to use the GPURegionOfInterestCallback ? > > cheers, > > guillaume > -- This message is subject to the CSIR's copyright terms and conditions, e-mail legal notice, and implemented Open Document Format (ODF) standard. The full disclaimer details can be found at http://www.csir.co.za/disclaimer.html. This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
