[osg-users] Best method for screencapture in OSG?

Robert Osfield robert.osfield at gmail.com
Tue Sep 23 09:50:43 PDT 2008

Hi Stephen,

Have a look at the osgscreencapture example for efficient streaming of
rendered images to the CPU.


On Tue, Sep 23, 2008 at 5:44 PM,  <haithcoc at gdls.com> wrote:
> I need to update an OSG based app that performs screen capture.  The
> existing app used OSG 1.x and readPixels.  It worked but I would like to
> move to 2.6+ and improve efficiency.  I am looking into the alternatives,
> but don't currently have the target hardware.
> Can any give insight into the benefits of the different means of getting a
> screen capture that can be transferred back to CPU/main memory?
> The app uses OSG to model a camera on the network and streams jpeg images
> at a target of 30Hz to client nodes.
> I have looked at the old and new prerender example (the existing app is
> largely based on the 1.x version of prerender).
> I have researched Frame Buffers, FBOs, PBOs, and the traditional
> readPixels.  Which of these is likely to be best for the described use?
> Is this complicated at all if this is done using MPV which uses OSG with
> SDL?
> I have searched Google and the mailing list archives, read the FAQ, and
> read "How-to-ask Questions the Smart Way", but have yet to find an answer I
> understand.
> We also have a somewhat different usecase which grabs the depth buffer
> (again with readPixels) from an orthographic projection above the current
> location on the terrain.  We use the depth buffer image and the linear
> scale of the ortho projection to convert to distance/height values.  This
> provides image width*height number of samples quite quickly, which we then
> have any system memory.  We currently process this on the CPU and send
> terrain elevation information to a separate dynamics app (potentially on a
> different machine).  I am starting to investigate what could be done on the
> GPU to improve this process.
> Thanks for any tips.
> Stephen Haithcock
> General Dynamics Land Systems
> 38500 Mound Rd.
> Sterling Heights, MI 48310
> MZ 436-40-15
> (586) 825-8573
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