So after I had previously taken my new PS3 Eye webcam apart and put in a piece of floppy disk to act as a IR filter, I downloaded the software from AlexP to let it run on my computer. Here is a test showing the camera placed under my screen.
The camera is elevated because I also tested the viewing angle of the lenses in both its clockwise and counterclockwise position (the lenses rotates to zoom in/out). The following diagram is roughly the formulas needed to calculate what size screen you can get from a certain depth:
(Thanks to noverflow for converting my rough drawing into the above nicer picture)
It doesnt do that high (1280x720), and for MT, 640x480 is plenty high, what is more important is the frame rate. Most people want the highest of both sides, fps and resolution, but the norm most tables are at is 640x480 at about 60fps. I think the bigger the screen gets the more you’d want to use 640x480 vs 320x240, but as far as I know, most people try and stick with the 640 one. Frame rate is more important because the faster it is the more accurate the camera can send your points of contact to the computer to be registered. If you watch videos of people’s MT, if you see a “cursor” or finger identifier trailing BEHIND the point of contact, it is most likely suffering from too slow a framerate...or in some cases, too slow a computer (but the computer demands arent too bad for Touchlib or tbeta, so it’s not usually the case).
TargeT:
Apply the formula backwards…
First convert to centimeters - 205 x 121 (approx.)
CW:
205/1.22 = 168 cm
121/0.94 = 128 cm
So...for your screen, if the camera is oriented clockwise, you would need a height of 168 centimeters. The width (121) is covered by 128 centimeters height, but some of the length would be left out, so you need 168 centimeters.
CCW:
205/0.89=230 cm
121/0.66=183 cm
So...for CCW orientation, you need 230 centimeters .
ok, well, im not sure how accurate your calculations are, but as long as Sony didn’t lie about the viewing angles, you can measure with this formula: tan(half of the viewing angle) = (half of screen size)/(distance). and since zoomed out, its viewing angle is 75, with an 81 length screen, you would do (distance)=(half of size of screen)/(tan(half of viewing angle)). so (distance)=(40.5)/(tan(37.5)). so (distance)=52.7806” which is 134 cm. i don’t think the height of the screen maters since the area of that the ps3 eye sees is a square. that is the equation that Ive been using for planning my Multi touch tablet ever since i heard of the ps3 eye. its about 30 cm off of yours. it might seem like alot, but since from the video it seems that PeauProductions derived his calculations from a small scale test, so when you blow it up to 81” the difference could increase..
NOTE: all of these calculations are assuming that SONY didn’t lie about the field of view of the PS3 EYE. (56 zoomed in, 75 zoomed out) ill explain the formula if you don’t fully understand it but i’m in a rush now…
TargeT:
640x480 is plenty accurate for most setups currently being built. There are two things in particular (that I can think of at least) that make this true. First, most MT apps are designed with interfaces that keep precision in mind (bigger interfaces, less ‘pack as many buttons into a small area is possible’ mentality). Second, most objects touching the screen are going to show up as more than one pixel - and the center of the object will generally be determined by the size/shape of the blob, resulting in sub-pixel precision (so even though your camera only sees 640x480 discreet points, the center of a blob might be calculated to be at 235.8759x344.1739. Of course, there’s limits, but that’s always going to be true. Considering you’re unlikely to see a projector (or LCD) with a resolution over 1920x1080, I’d guess you won’t need more than one 640x480 camera unless you start needing multiple projectors as well…
Actually, I have no idea if touchlib/tbeta or any other public software does the second part, but it’s certainly the way I’m did it.
TargeT:
640x480 is plenty accurate for most setups currently being built. There are two things in particular (that I can think of at least) that make this true. First, most MT apps are designed with interfaces that keep precision in mind (bigger interfaces, less ‘pack as many buttons into a small area is possible’ mentality). Second, most objects touching the screen are going to show up as more than one pixel - and the center of the object will generally be determined by the size/shape of the blob, resulting in sub-pixel precision (so even though your camera only sees 640x480 discreet points, the center of a blob might be calculated to be at 235.8759x344.1739. Of course, there’s limits, but that’s always going to be true. Considering you’re unlikely to see a projector (or LCD) with a resolution over 1920x1080, I’d guess you won’t need more than one 640x480 camera unless you start needing multiple projectors as well…
Actually, I have no idea if touchlib/tbeta or any other public software does the second part, but it’s certainly the way I’m did it.
Multiple projectors is exactly what I’m thinking, I often get a head of myself. rear Projection is the only way to get large contagious spaces from what I’ve found so far.
Im not saying my calculations would be 100% right , but even though I measured initially a small area, the angle shouldnt change too much. After I had measured and calculated the formulas, I put in the height of my box (47cm) and got the screen size that I am using...soo it worked for me pretty well.
Oh and even though I am in the USA, I dont like inches, being an engineer, so I chose to go with cm..sorry if it causes anyone any confusion.
yah, if u got about the same size when u use your actual size, then u r probobly right. I just ran the calcs backward with your numbers and the field of view is actually around 62 degrees. kinda sad that they lied by so much. im curious how they get their measurments. it does kinda decrease the wow factor of using the ps3 eye. but still worth it for the high res/ high fps. on the topic of veiwong angles, is it possible to make a wider angle lens for the eye? I know you can make the whole peep hole mod but I was gona try to mod an actual cheap wide angle lens. I heard it was done for the xbox 360 live cam.
I can just divide and multiply 
