Various pd/gem Qs

Johannes M Zmoelnig zmoelnig at
Mon Jul 10 12:27:18 CEST 2000

hi thomas, hi all 

> Some new questions:
> Don't know if I understand the camera object correctly. I only get it to work if I put it into a gemlist and then it only works for that single gemlist.
> Is it possible to get it working globally, for all gemlists and subpatches? The camera should influence the perspective of the complete scene, of course...
Yeah, this is a very known problem with the camera
i have already asked Mark before, and he said something about having the
camera object at a specified point in the rendering tree:: this is :
having a GemList with a very low or high priority (i've forgotten which);
you can modify the priority of the GemList by passing an argument to the
gemhead:: eg: "gemhead 1" will be very high priority and therefore be
rendered prior to anything else.

but however, i couldn't get this to work, no matter whether i used high or
low or no prioriteis; the only way it does *anything* is by putting it
on the top of a gemlist (as you described above - and this is really not
very satisfying, since it only takes effect on the specified gemlist)

therefore i have written a "view" method for the GemWin object (which
controls the whole scenery and therefore seems to be predestined to
influence the viewing point of the whole scenery) which is exactly what
you want (as i think)
BUT:: unfortunately this is not very stable (at least not on Linux-boxes);
if you are quick (for i hope, that i can applie a stable patch tomorrow)
and in Vienna, you can have a look at the "Haus der Musik" and see Gem
crashing every 15 minutes or so;
on Win98 I had it work for a quite long time (12-24h) without any crash; 
Since it is so unstable I have decided to use "translate" and "rotate"
objects for each Geo in the patch --- not very sophisticated...

I have also done a "fog" method and a material object (although I lost
formatted my harddisk and lost the latter...but of course I can do this
again if anybody get's interested)

other unstability issues ::
if i continue to "start"/"stop" the rendering engine, I will surely get
Gem (and PD, of course) to crash after "some" times; this is very
inconvenient and only on Linux

suddenly (and i can't remember of having changed anything in my
configuration) pd will cause a segmentation fault, every time i quit it
with having Gem loaded (without gem, the exit is fine as ever); first I
thought that my patching of the library (the view... methods) is really
wicked (which, by the way, it certainly is) but trying the original .dll
from Mark produced the very same crash
anybody experienced similarities ?

on Linux i get Pd crash (signal 11) everytime i destroy the GemWindow; i
think this only appears when using nVidia's detonator drivers
(i use kernel+GLX-0.9-3); with mesaGL I think destroying the window is as
good as on WinXX-platforms (but I am not sure about this)


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