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hi all,

i currently have an annoying problem, which i couldnt resolve
yet. i am using artoolkit using a firefly firewire cam (but this also 
happens with other firewire cams).  my artoolkit initialization code is 
pretty much simply based on the "simple" example app.
all in all everything is running as expected, but from time to time the
rendered camera image will suddenly turn somewhat darker for a few 
seconds, and then comes back to its old brightness. any idea why this 
could happen?

thanks,
alex

(i attached two very small screenshots showing the effect)

-- 
Dipl.-Inform. Alexander Hornung
Computer Science VIII
Aachen University of Technology (RWTH)
Ahornstrasse 55, 52074 Aachen, Germany

Phone   ++49 (0)241 80-21815
Fax     ++49 (0)241 80-22899
mailto:hornung@c ................
http://www.rwth-graphics.de

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hi again,
i think i found the reason and the solution is probably interesting
for some of you.
i wrote a combination of artoolkit, the open dynamics engine for physics 
stuff, and a new render-engine to integrate things like toon shading.
and the reason for the _sometimes_ darker camera image was actually
a single line of opengl code in the render engine where i set the 
texture environment to gl_modulate instead of gl_replace.
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
strange enough that i just leads to this error in "some" seldom cases.
(fun to debug...)
solution is of course to set
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
after rendering.

this makes we wonder, if it would not be better to provide an option in 
the artoolkit, so that it sets all neccessary gl states and so on before 
every rendering pass, so that integrated foreign opengl code does not 
interfere with the displaying of the camera images...
with around 30fps this should not be a big performance hit anyway, but 
providing it optionally using a kind of flag or whatever could help a 
lot in applications with lots of rendering work.

anyway, artoolkit is great ;)

best,
alex


Alexander Hornung wrote:
> hi all,
> 
> i currently have an annoying problem, which i couldnt resolve
> yet. i am using artoolkit using a firefly firewire cam (but this also 
> happens with other firewire cams).  my artoolkit initialization code is 
> pretty much simply based on the "simple" example app.
> all in all everything is running as expected, but from time to time the
> rendered camera image will suddenly turn somewhat darker for a few 
> seconds, and then comes back to its old brightness. any idea why this 
> could happen?
> 
> thanks,
> alex
> 
> (i attached two very small screenshots showing the effect)

-- 
Dipl.-Inform. Alexander Hornung
Computer Science VIII
Aachen University of Technology (RWTH)
Ahornstrasse 55, 52074 Aachen, Germany

Phone   ++49 (0)241 80-21815
Fax     ++49 (0)241 80-22899
mailto:hornung@c ................
http://www.rwth-graphics.de

At 1:07 PM +0100 24/11/04, Alexander Hornung wrote:
>a single line of opengl code in the render engine where i set the 
>texture environment to gl_modulate instead of gl_replace.
>glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
>strange enough that i just leads to this error in "some" seldom cases.
>(fun to debug...)
>solution is of course to set
>glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
>after rendering.
>
>this makes we wonder, if it would not be better to provide an option 
>in the artoolkit, so that it sets all neccessary gl states and so on 
>before every rendering pass, so that integrated foreign opengl code 
>does not interfere with the displaying of the camera images...

Alex,

What you suggest is exactly what is done by the function 
arglDispImage in libARgsub_lite (a replacement for libARgsub).

New projects should use libARgsub_lite in preference to libARgsub 
where possible. You can find the library, example usage (simpleLite) 
and documentation in ARToolKit v2.69 
(http://sourceforge.net/project/showfiles.php?group_id=116280).

Regards,
Phil.
-- 
Philip Lamb
Research Student,
Human Interface Technology Laboratory New Zealand,
University of Canterbury, Christchurch, NZ.
+64 3 3642987 x3070