[PD] still struggling with basic understanding of Gem dataflow

[John Harrison]

This is extremely helpful. I'm starting to "get" it. Comments/questions 
inline.

chris clepper wrote:
> There are two types of objects in GEM: pix and OpenGL. 
>
> Pix objects do work in the top to bottom manner like Pd DSP objects.
would [pix_coordinate] be an exception to this? I've been playing with 
it and it seems to behave the way you have described OpenGL objects and 
not GEM objects. I read the help patch about [pix_texture] reassigning 
the coordinate values, but that still didn't explain all the behavior I 
was seeing.
> The convention in GEM is to put the GL objects after the pix_ ones 
> showing that once the pix_ processes are done on the CPU it is time 
> for the GL processes on the GPU to start. 
I understand you to be saying that the GL processes will always be 
applied after the pix_ processes. If that is the case, then it sounds 
like there is no way to have [rotateXYZ] applied before [pix_rtx]. Makes 
sense.

For the more general case, is it correct that there is no way in GEM to 
give an arbitrary rotation of an image as input to a pix_ object since 
there is no Gem pix_ object with arbitrary rotation function?

Figuring that might be the case, I tried to build [pix_rotate] using 
[pix_coordinate]...and this led me to the question about about 
[pix_coordinate]

Using pdp_rotate, pix_2gem and gem2pdp, I did successfully build a pix_ 
rotator. On the chance it might be helpful to see, I attached a demo 
patch which feeds a rotated video stream to [pix_rtx] then rotates the 
stream back to the way it was. While it more-or-less works it seems a 
bit scabby. Is there a better way?
>
>
> There are lots of exceptions to Pd rules in GEM and there is really no 
> way around them.  It is kind of like learning English - I before E 
> except after C, excepting all of those words that ignore the rule.
As long as I can make sense of what the rules are, which objects break 
them, and some rough idea as to why, I'm cool with that.

Thank you again for your help. As Hans suggests, I'd like to find a way 
to help organize, then share this information, whether it be on the wiki 
or in some other meaningful way.

-John
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