[PD-dev] Inconsistency in behaviour using Gem... my fault?
Nick Bailey
n.j.bailey at elec.gla.ac.uk
Wed Nov 1 10:23:20 CET 2006
Hi pd community. I have a suspected bug but before I raise it with
the Mac developers, I thought I'd ask some experts to make sure it
isn't my fault.
Using pd 0.39-2 on Linux (Debian Sid) to do my development, but
wanting to deploy on my Mac Powerbook using "Pd-extended" 0.39-2
beta4 from http://at.or.at/hans/pd/installers.html on the Mac
(there's a 5th beta release on that site, but it won't even start for
me).
Problem involves a Gem patch. We want to divide a photograph up into
tiles, so each can individually cross-fade between one photo and the
next. I made a first rough cut of a UI to do this called
imageMixer.pd on my Linux box (it's at http://markov.music.gla.ac.uk/
boston.tar.bz2 - 465K). After playing with it for a while, I attemted
to transfer it to my PowerBook, and it sort of worked, but when
rendering was switched on, I got a continuous message:
separator : state->numTexCoords 4 != m_state.numTexCoords 0
repeated over and over again. The separator in question turns out to
be in [pd tile] which is in [pd tile_array] (at the bottom right of
the patch).
Playing around a bit more, I came up with imageMixer-mac39.pd. This
gets rid of the separator in [pd tile] and just has a gemhead feeding
both pix_image. This works fine on the Mac (though I was led to
believe you had to use a [separator] here... why not? Should it not
work?) but on the linux box it doesn't fade between two different
images, it fades between image and black.
The final attempt (imageMixer-2.1.pd) simply moves the gemhead
outside of [pd tile] and back into [pd tile_array]; this works on
both machines.
Now, this is my first ever pd patch (except for a very simple one I
wrote to demonstrate writing an LPC pd plugin to my students), and
certainly my first outing with Gem, so it's very likely I've just
missed the plot with the semantics of gemheads, separators etc. It
does look to me like there might be a bug in separator on Pd-extended
for the Mac though. It is after all a test release. Consequently any
comments directed to me regarding RPI (removal of pig-ignorance) or
style criticisms would be very well received. If people think it's a
bug, I'll file a report with the Mac packager (or maybe s/he's
already reading this?)
One last question. pd/Gem was certainly a rapid development tool for
the concert which is going to be in Boston MA in a few days' time,
but apart from the judicial use of [print] and numbers, staring at
the code, and bleating for help from my postgraduates, are there any
better ways of debugging patches? You'll have guessed from my email
address that I'm from a different programming background, and use gdb
and the like much more frequently. I've certainly learned to be very
strict about versioning. Messing around for an hour or so with a
patch, then not being able to use diff to see what one's ended up
changing makes one take particular care in that direction!
Thanks in advance for your helpful advice and comments,
Nick/.
More information about the Pd-dev
mailing list