There are lots of discussions regarding what setup is the best.
So I tried to write up some pros/cons, regarding both setups, since
I have build both setups. Please feel free to contact me, I will add
your input to this post..
FTIR:
* blobs are nice and clear
* setup needs an led frame which you have to make yourself (soldering needed)
* only allows touches with fingers
* requires a compliant surface, so that touches also get recognized during dragging operations
I still think that FTIR is a really good way to go, We just need to find a good
compliant surface. Right now, many are using a transparent silicone rubber,
on top of the acrylic, to get good recognition while dragging. Over that goes
the projection surface (tracing paper, rosco etc).. One advantage of the
FTIR setup is that you don´t need to build a box to get it working
(while DI setups need a box..). The other advantage is that the whole IR setup
is in one piece with the surface/screen, so handling is easier when moving the setup.
FTIR sheme:
DI:
* no need for a compliant surface, just an diffuser/projection surface on top
* no need for an acrylic, could use other transparent materials like glass as well
* no frame, allows for some nice box setups..
* no soldering, because you can buy the IR-Illuminators ready to go
* simple setup, difficult to get it working right
* fingers and fiducial marker tracking possible
* blobs are not as clear and sharp, when compared to ftir
Right now, I love DI! Because the dragging is soooooo smooth. I think
this is basically the best thing about DI, because it really makes it so
much more enjoyable. Plus you can track objects as well, using special
fiducial markers, that software can pick up and track them on the screen.
The biggest problem I had, while building my DI setup, was getting the
screen illuminated evenly. This is really the key, to having a good performing
screen. I always had one corner a little bit darker, or some spots (center)
brighter then the rest. But you have to get it even, because when setting up
touchlib you have to tweak the filters for the complete screen. So, if one part
of the screen is illuminated lighter then the rest, the fingertips will be
recognized well, while the in the darker part of the screen, they won´t. So you
can adjust the filters, that the fingertips get recognized in the darker areas as
well. But then, in the lighter areas, the fingertips will be recognized to early,
while not touching the screen. This can get very tricky while using software,
because you get a lot of unintended inputs.. so you have to get it even. It took
me about a week to get this on my setup.I tried so many positions for the
illuminators, there was always a part that didn´t work well. I tried diffusing the
light in front of the diffusors, bouncing of the box walls etc… In my previous
post you can see that I used a silver reflective material for a lighting shop to
get it right. It took a while, but it works now.
DI sheme:
So, who is the winner?
Honestly, I don´t know. Right now, I am focussing on DI, mainly because the ability to track
objects, and because I do not have to use silicone rubber. Since there is no software that can
track fingers and objects at the same time (reactivision tries to do this in 1.4, but I really haven´t
got it to work properly), this seems to be a little pointless right now. Please feel free to discuss this
using comments or via the contact form on the blog.
A remark regarding FTIR “only allows touches with fingers”, this must be a mistake, because we can use any object to interact with our NUI-box
Personally for me FTIR is still the winner, unless somebody comes up with an easy to mount setup, because setting up illuminators for days is not the way to go. In that mean while you can do tons of silicone rubber yourself.
hi grav,
well no, with “only allows touches with fingers” I really mean, “doesn´t allow object tracking”, so while you can use objects on your truely nice setup, you can´t track them….
mmh, this might be becomming a nice, controversial post:)
Is the lee filter 225 that you list equal to:
Rosco E-Colour #225 Filter - Neutral Density Frost
http://www.bhphotovideo.com/c/product/90649-REG/Rosco_102302254825__225_Filter_Neutral.html
I can’t find a place to buy it in a sutable size. The Rosco is the closest I found. Yet it is said that the Rosco blocks IR (?) If the Lee is unavailable, I assume mylar would be ok? Thanks.
oh, and I’m assuming the mylar people are using is the thinnest gauge 0.001″ thickness - with double matte finish? the supplier I looked at offered all of these options:
#Finishes: clear, hazy, matte, prepared (gel coated), pressure sensitive, metalized, transparent blue
# Gauges: .001″, .002″, .003″, .004″, .005″, .007″, .010″, .014″
# Treatments: Slip, Print, Anti-Stat, Silicone
Thanks!
hi foo,
sorry for the delay…. well I am not sure about the rosco 225 Filter, because I haven´t tested it myself. Could work though.. all I know, is that the rosco “grey”, which I used on my FTIR setup does not work with a DI setup, because its to thick. Not enough IR light gets through, so it didn´t work for me… regarding the mylar.
I am not sure which kind to use, because the only stuff I get here is basically tracing paper, not even mylar I think. It works pretty good, is cheap, but the projection is not so nice.. But recognition is just a good as the Lee filter. Did you check the vendors on the lee webpage? Sure that there is no reseller anywhere near you?
Thanks Tim, you are correct, I should have checked the distributor section of the website. I initially tried google but came up empty with my searches (found retailers selling mostly smaller sheets, and not rolls). I planned to use a friend’s 1920×1080 projector, an Optoma HD80. So, I assumed a projection surface of 72″x40.5″ would work, but I couldn’t find filter material this large. Let me know if you see any problems with this setup too…too big for the projector to ensure good resolution? will my firefly mv not have enough resolution? The lee material is available in 48″x25′ rolls though for a similar cost to what I was seeing ‘drafting film’ sell for. I believe david(whitenoise) used drafting film with good results. Is this what you mean by tracing paper? My understaning is that drafting film is usually .003 thickness mylar and the nuigroup folks are using the double matte version of this paper. e.g. http://www.draftingsteals.com/40369.html Drafting Film Double Matte 3 Mil Alvaflex 42 X 20Yd Roll @ $130 - for comparison, I found the lee filter roll of 48″x25′ for $140.
For anyone who stumbles here, the US based lee distributors are here:
http://www.leefiltersusa.com/LightDealers/LightDealersIndex.html
hi foo…
yea, i also got the firefly last week, i am only having problems with touchlib though. its just toooo slow. Nice camera though:)
well your setup is pretty huge, i really haven´t build anything that big, so i am not sure where to get projection surfaces big enough for that size. Remeber to get a fast computer too, what client software are you planing on using ? Since i mainly use flash, i wouldn´t go much higher than 1280×1024.. guess other software could handle more…
about the drafting film… yes it works pretty well, but the tracing paper (drafting film, mylar etc) is not the best projection surface. It works, yes, but i really like the dark lee filter more, because colors are more vivid and contrast is better as well. And its looks pretty nice when the projector is switched off too. But if you can´t get it in your screen size, then go for the drafting film… but maybe you should try to build a smaller table first, just my 2 cents..
Hi Tim,
great comparison! What would you recommend for a beginner building his or her first MTD? DI because of its easier setup (but needs a case) or FTIR because it is easier to configure (but needs compliant surface)?
Hey Tim,
I love your blog and i have been following your progress for a while now.
I have a question:
What is the projection surface your using for your rear di? I happened to have read your comment about Rosco Grey not being suitable for DI? Could you please explain?
Thank you,
Chaitanya
Hi Chaitanyamuppala,
yes you are correct, I thought rosco grey wouldn´t work with DI.
Turns out miketavius did get it to work, with enough IR-Light.
I am using the leefilter as meioned in an earlier post..
I also read that Gerrits Optitrans works pretty well.
you can read about it on the nuigroup forums:
http://nuigroup.com/forums/viewthread/962/
a great explanation for Di setups by the c-base group:
https://www.libavg.de/wiki/index.php/Building_a_MultiTouch_Console
Hey tim! Great job.
I took apart an LCD, and have been trying the DI approach
——–acrylic
——–lcd
/o\illuminator
/o\ webcam
kinda a test.. is there a way to actually get this working? or will i need to stick with the Ftir way. I would love the DI path. but dont know if you can illuminated the IR effectively threw the LCD display? have you read or seen anyone able to do this?
Thanks!
Hi Kevin,
personally I haven´t tried to disasemble an LCD screen. The last time I checked,
the biggest problem is Illuminating the LCD evenly (with “normal” Light). But check out the Nuigroup Forums, several members have tried to do this. Not sure what the progress is though..
tim
Hey tim!
It is a really great job.
As Kevin, I begin a DI-LCD
——————————————————————————— acrylic
——————————————————————————— lcd
/o/ illuminator \o/ webcam
But I have got a problem…. with the webcam I see a big white spot. I tried to tilt the projector but I can’t see any blob.
The only solution, for the moment, is to use a FTIR tehcnique but this is not what I want for my final project.
Thanks!
hi kevin…
not sure, but don´t you need some kind of diffuser on top of the acrylic?
As I said, I have not worked with LCD Screens, but with DI Setups you need some
kind of diffuser on top of the acylic, like some kind of tracing paper…