[PD] still struggling with basic understanding of Gem dataflow

[John Harrison]

I'm pretty determined to work through this! :-)

I thought I'd write a workaround to keep this conversation moving: My 
plan was to write the video to a buffer with [pix_buffer], then read one 
frame later and apply [pix_rtx]. I've done this workaround before for 
similar situations.

But I got stuck before I even got to [pix_rtx]. Please see the attached 
patch.

In the patch you'll see 3 toggles, all of which I would have expected to 
show a rotated image textured onto a rectangle. Only one of them does. 
They are numbered right to left.

Box 1 shows the output of [pix_buffer_write]. That shows a rotated 
image. Fine so far.

Box 2 shows the output of [rotateXYZ] before [pix_buffer_write]. That 
shows a rotated white box with no image textured. Why?

Box 3 shows the output of [pix_buffer_read]. That shows an image but no 
rotation. Why? This one is especially troublesome to me.

I'm trying to make my questions as specific as possible. Please 
understand I have looked at plenty of examples of [rotateXYZ] and I 
understand the object and have made full use of it. And I have 
previously read about [pix_separator] and know the archives that refer 
to it. There's something else going on here about dataflow with Gem that 
I don't get. I can make up 10 other examples with 10 other objects if I 
have to.

-John

John Harrison wrote:
> Thanks Hans. I know the example patch already and I have [pix_rtx] 
> working fine inasfar as I can get it to do what the example patch 
> already shows. I think my question is more about data flow and Gem. My 
> patch and [pix_rtx} are just an example of a more basic 
> misunderstanding I believe I have which has not been cleared up 
> despite many hours of work in Gem.
>
> Could somebody explain to me my [pix_rtx] in my example patch appears 
> to be processed before the rotation instead of after?
>
> -John
>
> On Tue, Mar 24, 2009 at 9:33 PM, Hans-Christoph Steiner <hans at eds.org 
> <mailto:hans at eds.org>> wrote:
>
>
>     I think this is an appropriate place to discuss gem.  In the Help
>     browser, check out:
>
>     examples -> Gem -> 04.video -> 04.videoRTX.pd
>
>     I had to do some trickery to get it working OK.  Check the
>     archives for details, I remember some discussion about all the
>     separators.
>
>     .hc
>
>
>     On Mar 24, 2009, at 3:35 PM, John Harrison wrote:
>
>         Attached is a small example patch of how I just don't get
>         Gem...still...
>
>         [pix_rtx] has a steady wave that normally flows from left to
>         right.
>
>         I would have thought that the attached patch shows me rotating
>         the image first, then applying [pix_rtx]. So it would stand to
>         reason in my mind I would see a rotated image with [pix_rtx]
>         flowing from left to right.
>
>         But that isn't the result I see. The patch has [pix_rtx]
>         flowing from right to left now. It is as if [pix_rtx] is
>         applied *before* the rotation instead of *after* as I would
>         have expected.
>
>         Grasping at straws, I have tried [pix_separator] between just
>         about every object, but that makes no difference.
>
>         What am I misunderstanding that makes the behavior of the
>         patch make sense? And...how would I get [pix_rtx] to flow from
>         left to right on a mirrored image?
>
>         -John
>
>         P.S. Are questions like this better on the Gem-dev list?
>         That's a developer list but at the same time I feel a bit
>         awkward putting too many Gem questions on a Pd list
>
>         #N canvas 962 171 305 227 10;
>         #X obj 29 -58 gemhead;
>         #X obj 29 -35 pix_video;
>         #X obj 29 44 pix_texture;
>         #X obj 28 72 rectangle 4 3;
>         #X obj 159 9 gemwin;
>         #X msg 136 -34 create \, 1;
>         #X msg 214 -33 destroy;
>         #X obj 135 -57 loadbang;
>         #X obj 29 17 pix_rtx;
>         #X obj 29 -10 rotateXYZ 0 180 0;
>         #X connect 0 0 1 0;
>         #X connect 1 0 9 0;
>         #X connect 2 0 3 0;
>         #X connect 5 0 4 0;
>         #X connect 6 0 4 0;
>         #X connect 7 0 5 0;
>         #X connect 8 0 2 0;
>         #X connect 9 0 8 0;
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>
>
>
>     ----------------------------------------------------------------------------
>
>     There is no way to peace, peace is the way.       -A.J. Muste
>
>
>

-- 
John Harrison
http://alumni.media.mit.edu/~harrison


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