I am having a very basic problem with GEM in pd (probably because I have started yesterday...).

I have a patch which manipulates input from my webcam and displays it as several (sixteen, to be exact) squares. I have separated the sqaure display into an abstraction, as it will be later substituted with DMX communication.

To the abstraction I send the square number (from which the position of the square is calculated in the abstraction) and the RGB numbers. I call the abstration from a for++ loop...

Everything works fine, the squares appear in correct places and with correct colors. However, the problem is, that each of them disappears when the next one is drawn!

How to correct that?

hmm, without seeing the patch it's hard to say, but here's a guess: the abstraction is called 16 times, but internally it has calculated the position for 1 square, so it just draws that 1 square 16 times, instead of 16 different squares.

there are two common ways to solve this:

1. create as many instances as you need and route information to them appropriately (I like to do this in Gem with 2 inlets and 2 outlets, something like this:

[inlet] [inlet]
| |
[t a a] [route $1]
| | | |
| [do stuff] |
| |
[outlet] [outlet]

and have a ladder like:

[gemhead]
|
| [1 moo, 2 baa, 3 quack, 4 woof(
| |
[myabs 1]
| |
[myabs 2]
| |
[myabs 3]
| |
[myabs 4]
| |
etc etc etc

2. using [repeat] from zexy or [until] / [gemlist] from Gem or "double gemhead idiom" (search pd list for discussions about these)

basically you repeat 1 gemhead's output 16 times, and count each repeat so you can do something different for each one, while reusing the same rendering objects in other places

Here they are:

and

They are somewhat ugly, as I said, I'm just starting...

Of course, I will be grateful for any critique or tips (e.g. I did not figure out how to use arrays of constants - they do not allow me to save them...).

as far as i can see, the LEDdisplay subpatch only contains 1 rectangle. if you want 16, then you will have to tell pd to make 16. claudius' post above has some clues on how to do that.

Thanks for the tips, I did it with [repeat] and [separator] objects. Works like a charm! Thanks again!