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