Re: [AGG] Animation in win32 with AGG

[Stephan A. <sup...@gm...>]

Vlastimil Mil=C3=A9=C5=99 wrote (2007-08-29, 15:44:44 =5B+0200=5D):
> Uhm, threads are tricky. They do not seem tricky, but they are. I have=20
> seen and worked on my share of threaded programs and there is usually no=
=20
> visible speed benefit. A poorly designed application with threads can be=
=20
> slower than a simple single-thread solution.
>=20
> Threads will only benefit you if you:
> a) expect that the time needed to render subsequent frames will be very=20
> variable

That is exactly the problem which I tried to solve in my application. I=20
wanted it to survive peaks of processing times which are longer than the=20
frame duration for a short period of time.

> b) or if you=27ll use more than one thread (and more than one processor) =
to=20
> work on multiple frames concurrently

Depending on what is happening in your rendering function, this could=20
indeed enlargen the requirements of your data structures considerably.

> Otherwise, if you expect the frame rendering times to be roughly the same=
=20
> and that one processor should be able to handle the animation nicely,=20
> just stick with single thread. You will save yourself a lot of useless=20
> work. Use UpdateWindow to make things a bit smoother.

Well. You need to know the requirements of your application very well. You=
=20
need to be quite sure that they don=27t become more complicated soon. For=20
example, let=27s add synchronous sound playback to the mix. Also in my=20
experience, the assumption that the rendering time stays mostly constant is=
=20
_very_ rare in real life. If your framerate is allowed to vary with the=20
computation time, than that is fine. But the original question was how to=20
harmonize the rendering and display frame rate. And for this particular=20
problem, I have found multithreading to be an elegant solution.

> And one more thing, you do not want to use realtime priority on your=20
> worker thread.

Yes, that is what I tried to say. The buffer switch thread mostly sleeps,=20
but it needs to wake up at the correct point it time. :-)

Best regards,
-Stephan