Lots of questions

[bencrossman]

Hi guys

Just started playing with our 2 SLIM cameras (no Optihub and using breakout sync cables) and have some questions.

- We have made a custom Optiwand. Can the markers on it be 3/4" or do they need to be smaller set.
- Same with the calibration square. Do they have to be 5/8" or can we use 3/4"
- We had trouble with one camera and I tracked it down to a faulty USB cable (supplied by Optitrack). Have you ever had reports of this before?
- We also can't seem to use a USB extension cable (5m brought locally). Do the extension cables need to be of a certain quality? Have you heard of this?
- We have used our own LED setup using 48 LEDS (http://www.ebay.com/itm/48-LED-Illumina ... 0724416007). Is there anything we need to be aware of here. Can the IR light be too bright? or focused? Do the built in LED on the V100 have a certain spread to them?

Sorry for all the questions

Any help would be appreciated.
We are prototyping a setup and trying to keep it cheap. When we have successfully got it working we could be ordering a LOT of hardware to recreate the setup across the world.

Thanks
ben

[NaturalPoint - Mike]

The marker size doesn't matter, as long as the cameras can see it appropriately during calibration and the centers of the markers line up.

I have seen cables go bad occasionally, generally due to damage or wear over time. It can effect camera synchronization.

USB extension cables are iffy, how long, what type, and where are you extending them?

The LEDs on the V100 are omnidirectional. It is possible to be too bright or not bright enough, depending on the camera's exposure. Experiment with it a bit. I'd recommend using the IR pass filter if you're using IR illumination.

[bencrossman]

I just read somewhere that if you connect cameras directly (not through Optihub) then it can go wrong if 5m or more so that might explain the cable problem. The extension Im using is another 5m so I guess 10m is way too long for a direct USB camera.

We are using the IR filters but it just seems that the exposure is hard to get right. Also if I set up projection tracking say for one camera and then play with the exposure, the point changes distance depending on the grey pixels around the point. Is this a problem or does the software not really use the point size and its the multiple cameras that allow it to track distance?

[bencrossman]

Ive played with it some more and got some better results. I was under the impression that the size of the reflective ball was used but it appears it more to do with multiple cameras seeing the same ball and all trigonometry. Is this true? If so then why do we have to enter the ball size in the projection tracking box?

[NaturalPoint - Mike]

That is entirely true. The points are created solely on geometry, not on relative size.

Projection tracking is a feature that was added to project the trackable into the 2D multicamera view, and has nothing to do with the method of tracking.

[bencrossman]

Ah ok, sounds we're going to need a lot more cameras

[NaturalPoint - Mike]

How large of an area are you trying to cover, and how many/of what type cameras?

[bencrossman]

Its a enclosed room of 4.8m x 2.4m
We are trying to track one human head (6DOF) and a held object (6DOF). The person will mostly be facing one of the long walls.



We currently have 3 SLIM cameras with 56 degree lenses. We do our own lighting using : http://www.amazon.com/48-led-Illuminato ... im_sbs_p_1

The salesman I spoke to said 3 cameras would be enough for this but if we need at least 2 cameras to see a point we'll need a lot more.

Do you think 7 would be enough? Hooked up to your "USB 2.0 Hub 7-Port D-Link"

[NaturalPoint - Mike]

Will you be trying to track them throughout the entire room? If that's the case, 4-8 may be appropriate. Keep in mind cable length restrictions would make a single hub less than desirable.

If you can be reasonably certain that they will be in a concentrated area in the room, 2-4 may work well.

[bencrossman]

Yeah throughout the entire room, I now have 4 cameras using a usb hub. Its a lot better but might need more cameras.