What do you do when you have 2 idle projectors by your computer? The answer is obviously a high definition projection area to be filled with lo.v.e. (lots of valuable experiments).

Two short throw projectors in one seamless desktop

I’ve been following the work of the Vision3D since 2009. This lab in Montreal is specialized in computer vision (recherche fondamentale et appliquée sur les aspects tridimensionnels de la vision par ordinateur). Lead by Sébastien Roy they have been producing (and sharing!) on calibration of projection surface (e.g. domes o/), multiple projector systems, and content toolsets.

lt-align manual calibration process

The Vision3D lab main tool in that area is Light Twist. This tool was presented in the LGM2009 with a live showcase of the system in a cylinder. In the last week I tried to have light twist going with a multi projector system (aiming to use this for a dome later on) but so far I’m stuck in the playback of content (and I suspect the calibration stage is wrong). Anyways, light twist will be a topic of another post, once I get it up and running.

Plugin enabled – video in the middle of the screens, desktop working normally

Since 2009 the light twist project shifted its focus from labs to end users. In 2011 they finally presented a new project called lt-align and lt-compiz-plugin. The lt-align is a software to quickly calibrate the screens alignment, very easy to use.


The Compiz plugin requires some fooling around with ubuntu settings, but once things are in place it works like a charm. I’m yet to make it work with Unity, so I can have real fullscreen across the desktops.

Recording of the alignment process and video playback

Elephants Dream – Stitched Edition 😉

Note: there is an extra package you need to compile the lt-compiz-plugin:`sudo apt-get install compiz-plugins-main-dev. And I didn’t have to restart compiz with ccp to make it work. Also I changed the shortcuts to start the plugin because Alt+F* were taken by other OS commands.

Time to make it real and project in a large wall

In this picture you can see Djalma Lucio, sys admin that oversees all the computer installations at Visgraf on IMPA. A great professional and a very funny guy to work with. Think about someone that actually enjoys opening a xorg.conf file. And you can also see in the right Aldo Zang. Check it out his ARLuxRender project – a plugin system for LuxRender “which allows to render scenes with mixtures of real and virtual objects directly, without post-processing”.

I hope to post more in the coming months in domes, projections, a special video project … 😉 I went on a 3-month leave of my work at UBC to join the research lab at Visgraf/IMPA, under the coordination of prof. Luiz Velho. This is the second week only, but it’s been already a great experience. And above all, it’s nice to be back home (Rio de Janeiro, Brazil).

Happy Twisting,
Dalai

What happens when an image fails to load in your system? It goes without saying that we need to find a non-intrusive way to analyze it.

It happened to me today. An image downloaded from the internet was failing to load in my project (a virtual art gallery for domes, more on that once it’s out). The internal framework involves to copy the image to the project folder and open it with Video Texture. For those unfamiliar with the Blender Game Engine, this is a python module to dynamically load and swap in-game textures.

In my tests all the images I tried were working. No exception. But of course it takes only a test-run with the client to get a crash 😉 One single image was enough to make me pull my hair.

Our beloved open image editor GIMP opens the image with no problems. In fact if I open it and save it I can open it in my project with no problems. So what’s wrong? Why can’t GIMP warn me about this problematic file?

Looking for ‘file inspectors’ I ran into this Binary File Inspector from Microsoft. It didn’t take more than a glance to spot the problem:

CMYK … Bingo! Opening the image in a station with Photoshop proved this was the issue.

For the adventure seekers out there, remember: open source tools are great. Yet you should be not afraid of getting out of your comfort zone once in a while.

Who could guess that Microsoft would be the cavalry to make it up for the lack of CMYK (and feedback) support on GIMP 😉 (or the lack of CMYK support in Video Texture, or me being short in tools for image forensics, …).

Have a great day,
Dalai