Hi all, sorry for my english.
After a lot of little and big issues I am finishing my setup.
It is a rear di, screen size 45 x 60 cm ( 29´). Height 85 cm (33 inch).
The purpose of this setup is to be able to do finger tracking AND fiducials, as a reactable setup.
I wanted to use the cheapest and the material I already had.
-common plexiglass ,
-tracing paper as surface projection on top of the plexiglass, and transparency sheet to protect the tracing paper.
-Lots of screws and other stuff.
-modified PS3 eye with 3 photo negatives on top to make visible filter.
-normal IR leds, visual angle 30 degrees , 920 nm, 2 groups of 16 leds.
-Macbook pro., OSX, snow leopard, macam driver. Reactivision, CCV.
-Benq normal DSP projector.
So, while doing this setup i faced LOT of different problems and found here so many advices, that I could solve almost all of them.
I think it would be a good help to others to make a list of the main issues for this kind of setup and to give the answers to them.
So these are a sumary of the issues I encontered:
-Positioning the mirror, projector and camera.
That was a big problem. Finally I am pointing the projector downwards and using the mirror to bounce upwards the light to the screen (keystone around 6).
So the projector must be at one side of the screen if you imagine that from the top, to not to block its own light. This makes the setup almost 20 cm larger in one side.
I had to do that because ALL the other solutions had a problem : The light coming from the reflexion from the plexiglas was going to the mirror, reflected, and was
visible in the projection, making strange artifacts. Anybody knows another position that avoids that?
The camera is pointing directly upwards, without almost any distorsion, which facilitates a lot the calibration with reactivision. As I am using the same lens mount after removing
the IR filter, I have only one focal distance, and 85 cm is the minimum height to see the full screen size.
As for the mirror, and camera, the most difficult part (and I did not reach a permanent solution) is to make a good and precise mount for the projector, that allows fine tunning and
is stable. I will post some pictures to show you my solution. My projector is atached to one of the MDF sides.
Fine tunning the height of the corners of the mirror (as for the camera) is very important to be able to get precisely the projection we want. I will post pictures of that.
How did you do it?
So, having good mounts for the mirror, camera and projector is really extremely useful, and helps a lot the calibration with reactivision (the grid we draw on paper can remain tha same, etc...)
Any ideas about that would be great.
The second big issue is the IR light.
Hot spots from the leds made impossible any solution except shadowing them (that is to cover a surface to avoid light from a led or its reflection to be seen by the camera)
(you can follow this thread to know more: http://nuigroup.com/forums/viewthread/11755/ )
Trying again and again, I found that for my setup, I was better to put the led stripes pointing with an angle of 45 degrees upwards to illuminate the opposite side from where they are set. They stay
at 40 cm from the bottom, and are set in the 45 cm (short ones) sides . I can move each led ( I let a portion of the led “legs” to be able to be moved) until I get an even illumination. It is working
great for fiducials recognition, and I get this good green dot on them that says the tracking is great. But it gets really difficult to have finger tracking with reactivision and this setup.
I know I have not enough IR light (only 32 normal IR leds) because I have to increase the gain to maximum, getting this unstable and grainy image.
Anybody could do blob and fiducials with this kind of setup?
I found a good think before getting the leds:
I can use normal bulb lights, and covering the light with photo negatives: visible light is blocked and IR is not, and it really works if the bulbs are not seen by the camera. But it gets too hot !.
The best way to avoid hotspots is to prevent reflections using a non reflective surface in the bottom of the plexiglass. But the problem is then that the image from the fiducials gets blurry and
it is not possible to track them.
there is perhaps as I read, a good surface that prevents reflections but does not blurr. That would be PERFECT!,
do you know which one could it be?
i will post some pictures tomorrow and detail some other aspects.
thank you !.