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Need advise/help to generate pixel precise output - Thnx

I am pretty new to vvvv and try to find my way around and I need advise/help to sove the following problem for an art installation:

I want to generate pixel-precise graphical output to 4 low-res LED panels with a resolution of 24x36 pixels each. The LED-panels are controlled through a control-unit that takes DVI-input.
What I need to do now is to exactly place 4 independent renderers, each in a specific & precise location on screen in order to generate independent output to the 4 LED panels. Also the output to the LED-panels should be exactly 24x36 pixels.

Could anyone give me advise on how to solve that issue? I am puzzled as the EX9 renderer by nature is relative in size…

Thank you so much…

I done this a few times, using a tiny portion of the renderer for an LED screen. I patched you something I would use, hope it helps!!

Trick is, you output a screen with X and Y resolution, and you want pixel price. In vvvv a fullscreen has a Scale of X and Y of 2.

So divide 2 by the real screen resolution, and you have 1 pixel, multiply that with how many pixels you need and you are good to go.

And a final step, you want to stretch the texture so every quad only shows 1/4 of the texture (That is if the 4 LED screens are placed next to each other)

CHEAP LED MAPP.v4p (21.4 kB)

2 hours later I realized the “actual backbuffer width” and “actual backbuffer height” pins of the renderer will give you the exact pixel dimensions of your renderer when in full screen…
(need to set the backbuffer width and height pins back to 0 for this to work)

dear westbam,

thank you sooo much. yes it helps a lot. Not that I have solved my problem yet, but I understand, that my approach wasn’t that far away regarding the basic logic of dealing with pixels (I have attached my much less skilled patch, yet its a bit different as I am trying to map a different renderer on each of the panels).
Yet, I still did not manage to get there yet (did not manage to place image/texture exactly on my LED-panels yet - and I have a slight idea that I might have different problems: first of all I cannot really go full-screen in VVVV - when I have the renderer active and choose “go to full screen” from the menue the button is grey and cannot be used. It might be a a problem of VVVV under Parallels on a mac, but I really don’t know. Altogether I have the feeling that VVVV isn’t running that smoothly under Parallels. Any experience with that?

Again, thanks so much!

140522_4-Planes-ABCD.v4p (37.9 kB)

To be honest, some people call a MacBook the best vvvv labtop, because it does NOT come with the dreaded nVidia Optimus driver (wich makes a lot of cool stuff not work on a labtop).

But these are more Mac questions, and that deserves another topic, where the Mac users off vvvv can help you ;)

I have 0 experience with a Mac. Perhaps your mac isn’t capable of running on 800x600 pixels? Or the “DVI to LED Box” doesn’t accept it, for your computer it is just a screen. Why not use a higher resolution?

Hey jfevm,

if your unable to go full screen but you need to position your renderer in an exact position and size use the “window (windows)” node to position and size your renderer and have it paint in the same place each time.
window (windows)
I run vvvv in bootcamp on my MBP and haven’t had any major issues, touch wood :)

Dear Westbam. Thanks again for your help. I have sovled my problem - basically using 4v under parallels seems to cause problems with pixel exact ouput on a macbook-pro with a retina display. Now I tried running 4v under bootcamp directly and voila, it works just fine. I am pretty glad…

Glad I could help, now I need to google what the difference is between Parallels and Bootcamp ;) (thought they where both just a way to get windows on a Mac)

edit: so “virtual machine windows under MacOS” vs “Real Windows”, makes sense now.