is this the correct setup for using DI method

acrylic
bellow that diffuser (is trace paper the diffuser??)
below that camera and ir source (leds) and light source

camera altered for ir detection and connected to pc

... is that it??

and the result i get is that i can control my pc by touching this surface?

Hey Manan,
You could use a diffuser on the bottom of the acrylic.  In that case, it would serve as both a diffuser and projection screen.  Depending on the thickness of your acrylic however, this could lead to a disparity between where your finger touches and where you “see” the touch on the projected image.  Here’s are the layers of my setup.

vellum paper
acrylic

I get a surprisingly good image using the vellum paper.  As far as the controlling your pc… touchlib has a mousedriver you could use.  Other than that, you’ll have to use special applications made for multitouch input via a camera.

thanx for the reply mike

the spl. applications you are mentioning are such as the 1s mentioned here vvvv etc.

so thickness should be less?

vellum paper - i doubt getting that here in india

also i was thinking that if we put the whole setup below the acrylic sheet then how does it become similar to the MS table ... what i mean is tht the MS table has a screen which is touched however in our case we have a whole setup below the surface to be touched and not the screen :(

another thing i wanted to ask was that linux has beryl which looks amazing (gr8 effects) so which software can i useon linux (this is least of my priorities as of now)

i’m not sure i understand what you mean with “what i mean is tht the MS table has a screen which is touched however in our case we have a whole setup below the surface to be touched and not the screen :(” you need a bunch of stuff below the screen to work, they have too. camera’s/ir source, etc. you just don’t see it.

and yes we do touch the screen even though not always directly. you could touch it directly but acrylic does not feel as good as projection paper and so. your fingers, if dry, kind of wants to stick to the surface and dragging operations doesn’t feel good.

the special applications mike was referring to is applications built that can receive more than one input. normal windows/linux/mac osx software only receive a single mouse click at one time. multitouch application need to be able to handle an infinite amount of inputs and handle that to work correctly. that is where touchlib, vvvv and so come in.

Touchlib, vvvv and now flash (through TouchEvent) does the tracking of where a finger was pressed and where it was moved and lifted and so. so by using those as the tracking software, you can get the touch events into applications.

there are a number of applications that you can use at the moment, touchlib has some that come with the bins (available here, i have a photoapp, available here and there are some more, just search to forums. if you’re looking to create your own apps, just check to forums, there are a few posts on where to get started. oh, and touchlib works on linux.

hope this kinda answers your question

thanks a lot donovan for putting things in some perspective ...

what i was saying is that in the MS table we directly touch the screen howver from what i have gathered from the illustrations i have seen is that in this setup we touch an acrylic sheet (example) now how do i put a screen in between the acrylic sheet and camera, ir setup ?

layers in this setup:

acrylic sheet
camera+ir

display on another device

layers in MS table:

screen
camera+ir

display on the screen

now how is a touch on the screen captured by the cameras and ir when there is a screen in between the touch panel and the cameras

if i confused u further i will make some illustrations so that it becomes easier

i’m think i’m starting to understand. i don’t have a DI setup, so i’ll go with what miketavius said.

we have a projector that projects the screen onto the (in this case: vellum paper) which is lying on top of the acrylic sheet. the ir that is being shined onto the vellum/acrylic the gets reflected back to the camera. when you press a finger you get a bright IR ‘blob’ that the camera sends to the tracking software… the IR gets reflected through the screen/tracing paper/acrylic so thats how the camera sees it.

to put a screen in, it’s not really a screen, more like a projection surface, you can just stick it to the front or back of the acrylic. not sure on which material to use though.

miketavius your screen looks like its working really well, what projection surface are you using “EDIT: never mind ive seen on your blog” and how thick is you acrylic?

Edit: Anyone:  But still wondered how thick acrylic to use with DI?

Thanks

Hey Diagdave,
I’m using a really basic setup at the moment, consisting of 1/4” acrylic with a sheet of vellum paper on top that I purchased at a craft store.  It’s the Martha Stewart brand vellum… specially designed for multitouch applications I also have a few yards of Rosco Grey on the way that I plan on testing.

Hehe, Martha Stewart brand computer hardware :P
I’m curious about your IR LEDs there. Are they working well? Could we see a picture of the setup? I can’t decide how to set mine up…

I haven’t worked on anything new regarding the rear-lighting of my display in a few days.  As soon as I have something I’ll be posting back here.  I’ll usually post things to my blog first and then here… so you can always check there.

im glad people are starting to work with DI it seems to be the way to go

Hey - I have just started attempting to build a DI table, and we have the IR’s placed close to the bottom of the table, and we get a big reflection off of the arcylic.

We’ve tried a couple of different ways of placing our IR’s, and so far we get the same result, a big reflection off the acrylic right back into the camera.

Is there a certain way we have to place our IR’s?

-Steve

Hey Steve,
Check out this thread http://nuigroup.com/forums/viewthread/421/.  It might be of some help.

Thanks, I’ll give that a try =)

guys i have come up with a rough layout of the DI setup from what i have gathered through the forums and blogs ... iv made it in PS ... image is below ... please tell me is it correct, after that i will move on to the next query ...

also 1 more thing i can enclose this setup ina normal box made of wood or anything ???