marco zoncu schrieb:
>
> Is it possible to use OpenGL libraries in a rtlinux
> task?
Don't try this at home! :-)
To be serious: IMHO it is not necessary to use
rtlinux or rtai to do this kind of jobs, nor these
hard real time implementations are intended
for stuff like this ...
What you need is "quality of service" (QoS), what
i like to call "Multimedia Real Time Scheduling" :-)
There are several ways for optaining this:
Have a look at www.timesys.com. There you can get
patches for a kernel, that guarantees i.e. 40ms in a
period of 50ms to be assigned to the process handling
the 3D stuff. This will allow absolutly smooth 3D
rendering - as long as the scenario isn't to complex for
the card to handle and thus the scene refresh rate doesn't
fall below ~25 fps, of course.
Instead of using the above mentioned Linux/RT
(formerly called Linux resource kernel, "Linux/RK"),
you could use the stuff from montavista. The kernel-patch
itself is yartli (yet another real time linux
implementation - that doesn't work very well, BTW), but
there is a simple user space utility that can be
used with an unmodified/usual kernel as well:
"rt" just places itself into SCHED_FIFO - like
David Olofson already explained - and then calls
the given command that will run in the same scheduling
space. This means, you can virtualy run any program in
Posix-Realtime-space even when it isn't designed
for doing so. For me, this works fine using an
Nvidia 2GTS based card (with NVdriver) and
several 3D-games :-)
But beware: ensure that the X-Server and the
Window-Manager are running with a higher
priority as the 3D-program, because otherwise,
the computer might easyly seem to be freezed:
the machine is rather busy with
redrawing the 3D-application, but doesn't get
any new input from the X-Server/Window-Manager,
because these processes are never scheduled any
more)
Also, having a bash running with the
highest priority located on a serial terminal
is basicaly a good idea when using the
command "rt", to have a backdoor in case
the X-Server loops :-)
usage: rt [priority] <program>
download: ftp://ftp.mvista.com/pub/Real-Time/utils/rt.c
Of course, there are more real time linux implementations
(qlinux/redlinux) out there which could do the job
as well ... but ymmv.
Bernhard
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For more information on Real-Time Linux see:
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