September 2007 Archives

When I tested for the first time my homemade multitouch display setup, I was too excited at the beginning to complain about the lack of sensibility. I had to press hard on the rear projection film to let the webcam detects the "blobs" of the infrared light bounced out of the acrylic. Later I understood this and I decided that it was the time to get a compliant surface made of silicone rubber as I was reading on the NUI Group forums.

I had a lot of doubts regarding the preparation because, of course, I never used this kind of material so I didn't had a clue of how to work with it. But the need was so strong so I decided to try at least once. Half a Kg of silicone rubber costed me 40 euro so I decided that this was my maximum budget to give a chance. But of course I didn't want to waste it!

Anyway, at the end of the game, I have to say that it was far more simple than I was expecting. I have to say also that I spent some time thinking about all aspects of the preparation process in order to avoid to waste the only chance I had for stupid mistakes.

I had great results regarding the silicone rubber layer even if later I had the surprise that, in my case, this layer alone with the rear projection surface won't work: I had to add an additional layer made of sketch paper to have the great sensibility that I was looking for.

I intentionally filmed all the preparation process thinking to make a video that may be helpful to someone else that is in the same situation I was, so, now that I saw the good effects of the silicone layer and after some (too many) hours of video editing, I can finally say:
HABEMUS VIDEO!



I really hope that you enjoy the video and that it may solve out any doubts you may have about the preparation of the silicone layer. Feel free to comment this post to ask for additional aspects or questions that I forgot to mention in the video or in the past posts. I would like also to know if you're going to prepare such compliant surface and, if you already did it, if it is working out for you even without the additional sketch paper layer.
Enjoy!

After I successfully tested the sketch paper I promoted the silicone rubber layer to the status of "useful". So I proceeded to acquire from the camcorder the video of the silicone layer preparation that I shooted two weeks ago.

Actually the video is nearly two hours long, so I will take some time to me to edit it and shorten to a more reasonable lenght but without loosing important informations. So, if you're going to prepare a silicone rubber layer by your own and you have particular doubts or questions, feel free to comment in this blog and to ask, so I can try to answer your questions and to keep in the video not only the informations that were important to me.

I posted here just those two images for now so you can get a rough idea about how I made it. I think I can post the video in a week, hopefully less. In the meantime I really suggest you to take a look at the compliant surface topic in the NUI Group forum.

Finally I was able to use some spare time to buy and try the tracing paper, to be honest, I din't post the tests done with it because it didn't worked out as expected! Sorry for being away so much time!

Of course there's another reason why I'm writing this post, I could not be so motivated by a tracing paper flop!

Last sunday, after I wrote the last post in which I said that I didn't have the tracing paper to test, a friend of us came home. Before she came, I was speaking with her on the phone and, knowing that she's an artist and she's always experimenting a lot of materials, I was asking her for a small piece of tracing paper. She brought an entire roll of sketch paper saying that she didn't had the tracing paper but this was so similar to it and I could give a try. I really have to say: THANKS CAMILLA!




If you look at the video you'll understand everything. Infact the tracing paper is not working as expected. I think that this is due to the fact that the tracing paper is too smooth and bright and it just sticks on the silicone rubber like the rear projection was doing alone. This partially sets off FTIR on the whole contact surface and finger touches are not so bright and recognizable.

The sketch paper is instead less smooth, more porous and even if it sticks a little bit on the silicone rubber, it detaches from it very quickly. As result it gives very good and usable blobs with just some persistance but anyway really a good behaviour compared to what I got from the tracing paper.

Luckily this is happening also with the projection film on it and not only! With the whole setup that is: silicone rubber, the sketch paper on it and the projection film on top I have constant and bright blobs even when I quickly move the fingers around. With just the bare silicon rubber I had great blobs that become very faded and less recognizable when moving the fingers.

I'm pretty happy of this results, hopefully this is the solution to the silicone rubber failure. Now I feel really more confortable with my multitouch table and I'm ready to go over. Even if the sketch paper roll width is smaller than my plexiglass I already covered the whole display surface with it, using two stripes. I hope that the background remove feature of the multitouch software may overcome the possible issue of the paper junction line. On top of all, I really hope to find some time during this week because I don't have enough time today to test the whole screen setup! But, don't worry I have anyway other news to post so I will not leave this blog alone for another whole week!
Stay tuned!

Thanks to the first great suggestions from Cirrus and Cerupcat from NUI Group, this morning I tried an early workaround to solve my problems with the silicone rubber. Some indications came out also from Gravano and, actually, we're quite sure that the silicone rubber failure is most probably due to its excessive stickiness.

This silicone rubber stikiness is the cause of the high cohesiveness of the rear projection surface on it and this frustrate the whole screen surface setting off the FTIR effect without any finger touch. Most probably this is why any other touch is not detected and why it seems there is low IR light: because it exit the plexiglas on the whole surface and not only in the touch spots.

To confirm those assumptions, as Cirrus suggested, I tried to place a paper sheet on the silicone rubber and tested it with and without the rear projection film on it. Cirrus rightly suggested to use tracing paper but, unfortunately, I don't have it at home and today is sunday, so I gave a try with normal A4 printing paper. Here are some pictures:

The above picture is the IR camera view that shows good blobs of my fingers on the bare silicone rubber layer. This is a little bit more than what I should have also with the rear projection film on it. But unfortunately this is (still) not happening.

The above picture is made placing a paper sheet on the silicone rubber layer. It is sticking anyway but really less than the rear projection film. The stiked paper makes a noisy pattern and just around the three fingers touches.

Last picture is with the rear projection film on top, so the paper is laying in beetween the silicone rubber and the projection film. As you mai notice, the paper is adhering not only around the three fingers touch but in the large area where it is covered by the projection film, this is because the (even small) weight of the projection film is pressing it on the silicone.

This result is really really more relaxing than what I got on the first silicone rubber test. The blobs are slightly visible using a sheet of paper beetween the two layers! This means, of course, that tomorrow I will run to the shop to buy a piece of tracing paper big enough to cover the whole screen. The tracing paper should work better than the normal one, so I hope to get brighter blobs.

I don't want to consider this issue closed and run too further but, if the tracing paper will work, next step will be to build an holding structure for the screen, so I can avoid to use the kitchen chairs to hold it and switch to a pretty stable and fine-tunable setup.

I've just completed the frame for my multitouch display and I could not resist from making an early test tonight!

To be honest, I have nothing to be enthusiastic for...

This is because this first test went really really bad. I had no usable "blobs" at all! I made also a short video that from the IR camera's view shows no blobs with the rear projection film applied. To be more precise, I had great effect on the bare silicone layer, the blobs were really clear and fast responding. As soon as I place the rear projection film on it all that magic effect just disappears. You will see also in the video that it is the same with two kind of projection surface: the Peroni Panorama that was kindly offered by Peroni and the Rosco Grey that I had from Gravano of the NUI Group who was also the man that successfully used it as first. Both films gave bad results in any position, rough surface up or down.



This is bad, I just don't want to think that my efforts for preparing the silicone rubber layer went wasted. To find some information and answers I posted in the NUI Group forum and also sent an email to Gravano who already helped me in the past. I'm really hoping to have good informations or hints from someone that will help me to have  this display finally work as expected!

In the ending part of the video, you will see that the nails tip are slightly visible. I'm still thinking on this because it demonstrate that, somehow, my setup could work. Actually I'm thinking about to perform some more tests increasing the IR light in the plexiglass by putting more IR LEDs in the frame or just better polishing the plexiglass edges (yes I was probably too quick in doing this at the beginning). On the other side I can try the other models of rear projection tissues kindly provided me by Peroni. For now, apart from this post, there's nothing I can do at 2 a.m. apart from going to sleep.....but....I have to find the solution!

Finally I arranged to prepare a silicone rubber layer to use in the multitouch display. I will use it to improve the coupling beetween the plexiglass and the rear projection film so that the display will be more sensible to finger touches and will require no more hard pressing to detect touches, yes, it is also an hope!

If you're trying to do the same don't worry! I video recorded the whole process and I will post a video as soon as I'll have enough time to edit and shorten it because actually it is 50 minutes long!

Ok, I still don't know exactly which are the results but I can say that it was really more simple than I was supposing, and this could be a good news too. The silicone rubber needs at least 12 hours to cure completely, so, since tomorrow I'll be at work at least until 6:00 p.m., I will know the results tomorrow evening, hoping that I didn't wasted the 40 euros (yes, silicone rubber is not that cheap).

In the rest of the week I should be able to complete and assemble the frame for the display so, luckily this weekend I'll be testing this new element and preparing the video of the silicone rubber layer preparation.
Stay tuned!

Finally I decided to build a wooden frame for my multitouch display. Basically I'm trying to build a light frame that may hold the plexiglass with the alluminium frame holding the IR LEDs together with the projection surface and the compliant surface that I'm going to make with silicone rubber. Here you can take a look at the actual stage of the wooden frame, it is quite complete, the glue is drying! On the right side you can see the silicone rubber I bought to make the compliant surface.

Once the frame will be ready I hope to handle more comfortably the display so I can go on at least with the software. That's because actually I do not own a video projector, I'll use just to test the software behavior.

Next step, as I was saying, will be the compliant surface. Actually the rear projection surface has a bad coupling with the plexiglas. This means that I need to press quite hard on the display in order to have workable "blobs" or decent reflected spotlight under the finger touch. I'll prepare a thin layer (1 mm) of silicone rubber to place beetween the plexiglass and the rear projection film, so the silicone rubber itself will be the material that will set off the FTIR effect and reflect IR from the pressed areas. This material seems to have a very good coupling with the plexiglass because it is so smooth and adhere perfectly without leaving micro air bubbles beetween itself and the plexiglass when pressed on to it. Of course this is also an hope!

As the great suggestions from Gravano's blog, I'll put the silicone rubber on the plexiglass panel and flatten it with an alluminium bar (it will be one piece of the alluminium frame holding the LEDs). To be precise I have to use some guide at the sides of the plexiglas that needs to be 1 mm higher than the plexiglass itself. Actually this is my problem: where I can find stripes of whathever hard material that are about 11 mm thick?

What is the plus of a wireless connection? That it doesn't use wires! (easy)
What is the plus of a wireless netwok? That it doesn't use a lot of wires! (quite stupid)
What is the plus of a wireless device? That it may connects to several other devices without the need of new cables (again)
Why should this interest me? Because those factors may lead to a new concept of networks.
Let me explain.
If you own a wireless access point, you're probably using it for browsing the internet lying down on your sofa. This sounds good but, from one poin of view this way you're wasting your device. Why?
Because if you have a wireless access point (AP) and the guy living in the upper floor has another AP, and the family living in front of your house have another AP and so on, you can use your AP to connect to the upper guy. He may use his own AP to connect to the family on the other side of the street. They may use their AP to connect to other people as well. This way, probably in the near future, you're not using anymore your AP to connect to the Internet paying also an internet provider, this way you become Internet and your connection costs just the energy needed to power up your wireless access point.
Sounds good? YES!
How it is called? Wireless mesh networking or MANET.
Can I do it now? YES!
Can I really use it now? Well... it is a technology still in development... there are some "dark sides".....but....

Do you want to know a little bit more? Ok, so this means that this post was good enough to introduce the new Project section of this site in which I'll resume and write down some of my works in this field.
Check out the new Wireless Mesh Networking page on BlaXwan's!

Probably you already saw the page called Multitouch Display. which is in the Projects section of this site.
Probably you were just scrolling it trying to figure out what this bunch of LEDs, wires and plexiglas are used for.
Probably you perfectly understood what that page was talking about but you thought that it can't work.
In every case, I was finally able to upload a video that I recorded the first week of August, it is the video of the first test of my Multitouch Display!

Here we go:



Please excuse me for the poor quality of the video but my camcorder is not that smart in poor light conditions...
Anyway, as you have seen there are a lot of improvements that I have to do to let this multitouch display be really functional. First of all I should improve the alluminium frame that surrounds the plexiglas in order to have better stability and higher IR light (I've just bought some wooden stripes to do it). Then I have to build up a small structure to hold the screen itself and the webcam in order to have a more stable setup and calibrate the webcam position to have more precise blob detection. Last but not least I need a compliant surface that will improve the coupling beetween the plexiglas screen and the backprojection surface because actually the display requires quite a hard pressure to let the webcam detect the touches. In the NUI Group community a lot of people is using a thin layer of silicone rubber as a compliant surface and seems to work well. Actually I'm still trying to find a good supplier for this uncommon material. With this kind of material the display should be really more reactive and a light touch should be enough to activate it. This way it should also be able to recognize different levels of pressure.......it's also an hope!
Once all my hardware issue will be solved I will move on the software aspects and this should be a more challenging field!
Enjoy the video and.....stay tuned!