which cameras for active IR tracking

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zsero
Posts: 15
Joined: Thu Mar 03, 2011 5:05 pm

which cameras for active IR tracking

Post by zsero » Thu Mar 03, 2011 5:28 pm

Hi,

Can you tell me what differences are between the different NaturalPoint cameras when used for active marker IR tracking? I would like to use some camera for active marker IR tracking, and I've read in the Camera SDK that it supports cameras more affordable compared to V120:SLIM. I am a student and thus on a tight budget. What really made me excited about Camera SDK is the support for TrackIR cameras. As I wouldn't need most of the advanced features of V120:SLIM cameras, like the IR illuminator or the filter switcher, or the support for 3D tracking tools, they look like good candidates for me. Are there any limits using TrackIR 5 for example compared to V120:SLIM, if I don't need 3D tracking nor passive IR support nor filter switching?

I have some questions generally about all NaturalPoint cameras which are not clear to me:
- Do different NaturalPoint cameras process IR blobs inside the camera and if yes, how many IR markers do they support? In cameralibraryglobals.h I've seen max objects 500, but it seems a bit too much. Tracking 500 IR blobs in real time would take a huge amount of processing, not something I can imagine happening in a low power on-board chip. Is it really supported?
- How is it possible to have high quality MJPEG output and low latency blob detection at the same time? Is the camera running low latency blob detection on-board, parallel to outputting MJPEG?

And some questions about Camera SDK support for TrackIR 5 cameras:
- What kind of output modes does this camera support? In my case all I'd like to have is the coordinates of a few IR dots, maybe up to 10 dots. Is it supported on a TrackIR 5 camera?
- What would be the most important benefit for me in investing in a V120:SLIM system over a TrackIR 5 system?

Zsolt Ero

LinusA
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Re: which cameras for active IR tracking

Post by LinusA » Thu Mar 03, 2011 5:47 pm

[quote=zsero]
- Do different NaturalPoint cameras process IR blobs inside the camera and if yes, how many IR markers do they support? In cameralibraryglobals.h I've seen max objects 500, but it seems a bit too much. Tracking 500 IR blobs in real time would take a huge amount of processing, not something I can imagine happening in a low power on-board chip. Is it really supported?
[/quote]
I can't tell you the exact limit, but I can tell you that the required processing power is not that much, so it should be possible. The cams do a thresholding on chip, and then they find regions, i.e. connected pixels/areas, of which they calculate the center (weighted center of mass) and other properties. All that is doable. Mind that the cams don't do actual "tracking" on board, so you don't get any information between frames, i.e. whether one certain marker / blob is the same you saw in the last frame. (This is unlike the Nintendo Wiimote for example, but this device only supports 4 markers).

I don't know what exactly you want to do, but until now, I personally never ran into a maximum object/marker limit. If it's 500, than that seems really much to me, and probably enough for virtually all use cases.

[quote=zsero]
- How is it possible to have high quality MJPEG output and low latency blob detection at the same time? Is the camera running low latency blob detection on-board, parallel to outputting MJPEG?
[/quote]
No, this doesn't happen at the same time, at least not with my V100R2 cams. You get either the MJPEG picture, or a thresholded pic, or the "Precision mode" (I don't know if that's available in all cams, read the FAQ / spec). In precision mode, the pic is thresholded, and you get the raw "interesting" bits uncompressed as grayscale (up to a certain bitrate limit), the rest is black. Neither MJPEG nor raw (uncompressed) modes support automatic marker/object detection. All other modes do (again, with the V100R2 cams).

Birch
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Re: which cameras for active IR tracking

Post by Birch » Fri Mar 04, 2011 1:39 am

Hello,
Do different NaturalPoint cameras process IR blobs inside the camera
The amount of processing performed in the camera will depend on the video mode. Hardware Object mode will perform nearly all the processing in the camera, other modes do some but not all of the pre-processing in the camera.

The main operating mode of the TrackIR 5 (BitPackedPrecisionMode) is a version of Segment mode with enhanced resolution.

Please see this post for a comparison of the main video modes.
http://forum.naturalpoint.com/forum/ubb ... #Post42942

how many IR markers do they support? In cameralibraryglobals.h I've seen max objects 500, but it seems a bit too much.
A TrackIR camera can transmit between 5 to 15 bright objects depending on the video mode and size of objects. For OptiTrack cameras it will also vary, however the maximum transmitted will typically be between 100 to the limit supported by the Camera SDK (512).

What kind of output modes does this [TrackIR 5] camera support? In my case all I'd like to have is the coordinates of a few IR dots, maybe up to 10 dots. Is it supported on a TrackIR 5 camera?
TrackIR 5 cameras support standard Segment mode and the enhanced resolution Segment mode (BitPackedPrecisionMode) mentioned above.

A TrackIR may be able to meet the needs you describe.

Also see this thread :
http://forum.naturalpoint.com/forum/ubb ... #Post45219

What would be the most important benefit for me in investing in a V120:SLIM system over a TrackIR 5 system?
In a general sense, the TrackIR 5 is a great device for the specific use it was designed for - which is precise and responsive head tracking in consumer games and simulations. OptiTrack cameras have been designed to meet broader and more demanding needs ranging from engineering grade tracking to professional motion capture.

More specifically :

* OptiTrack cameras support camera-to-camera sync, TrackIR cameras do not. The sync allows multiple cameras to expose at the same time which is important for 3D tracking (and more generally for correlating data detected by one camera with that of another).

* OptiTrack cameras are USB 2.0 Hi-Speed (~30-40 MB/s), TrackIR cameras are USB 1.1 (~500 KB - 1.5 MB/s). The bandwidth difference means a TrackIR can detect and transmit far fewer objects than a OptiTrack camera.

* OptiTrack cameras have global shutters and support strobed illumination, TrackIR cameras do not have either. These features are used to greatly improve object detection and reduce unwanted background objects.

* OptiTrack cameras support Hardware Object mode and Precision Greyscale mode. The TrackIR 5 does not support Hardware Object mode. Precision Grayscale is available for the TrackIR 5 but is not practical due to bandwidth limitations.

* OptiTrack cameras include very high quality lenses with very low distortion to improve the precision and accuracy of their tracking performance. The lenses on TrackIR cameras are good, but not in the same league :)

* Official support for the Camera SDK is only provided when used with OptiTrack cameras. Customers are welcome to use TrackIR cameras with the SDK but support and assistance will not be guaranteed if issues are encountered.


You can also find a comparison of OptiTrack Cameras here :
http://www.naturalpoint.com/optitrack/p ... rison.html

zsero
Posts: 15
Joined: Thu Mar 03, 2011 5:05 pm

Re: which cameras for active IR tracking

Post by zsero » Fri Mar 04, 2011 4:50 am

Thank you both for your answers! There really is a lot of benefit in Optitrack cameras, so it's not an easy choice, but maybe I can keep using TrackIR 5's till I have some results and find someone to support my project.

One area is still not clear to me:
- How do various cameras (V100R2, V120, TrackIR 5) focus? (I mean optically). Do they have a small aperture, like F8 or F11 thus they don't really need focusing? If it has small aperture, how can it handle low light situations (like passive markers)?
- Or they have manual focus on Optitrack cameras and fixed focus in TrackIR 5?
- Would it degrade the performance of a TrackIR 5 if I'd like to use it with objects 2m away from the camera? If it's made to be used on top of LCDs then I'd bet it has fixed focus at about 80cm, but I don't know what happens at 2-3 meter.

And just a quick question about the detection modes:
- Do all detection mode provide sub-pixel precision? I'd guess precision greyscale could get better than 1/10th of a pixel, but what about other modes?

Birch
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Joined: Thu Jan 30, 2003 5:00 am
Location: Corvallis, Oregon

Re: which cameras for active IR tracking

Post by Birch » Fri Mar 04, 2011 2:19 pm

How do various cameras (V100R2, V120, TrackIR 5) focus? (I mean optically). Do they have a small aperture, like F8 or F11 thus they don't really need focusing?
Or they have manual focus on Optitrack cameras and fixed focus in TrackIR 5?
The cameras are focused to infinity at the factory and do not have auto-focus. Due to the lenses they use the area in focus will start about 1.5 feet away from the camera. The lenses on OptiTrack cameras can be manually re-focused by the customer if needed. The focus cannot be adjusted by the customer for TrackIR cameras.

See this chart for information about OptiTrack lenses :
http://www.naturalpoint.com/optitrack/p ... rison.html
If it has small aperture, how can it handle low light situations (like passive markers)?
In OptiTrack cameras retro-reflective marker detection is facilitated by the IR strobe and global shutter. These allow for detection up to 30-45 feet depending on the camera model and marker size. With a TrackIR 5 the detection distance for retro-reflective markers is up to about 6 or 7 feet.

Would it degrade the performance of a TrackIR 5 if I'd like to use it with objects 2m away from the camera? If it's made to be used on top of LCDs then I'd bet it has fixed focus at about 80cm, but I don't know what happens at 2-3 meter.
The impact on performance at 2-3 meters for the TrackIR will mostly have to do with the size of the detected objects. Objects appearing larger to the camera tend to be tracked with greater resolution than small ones. As you move further from the camera the apparent size of an object will diminsh.
Do all detection mode provide sub-pixel precision? I'd guess precision greyscale could get better than 1/10th of a pixel, but what about other modes?
All tracking modes provide sub pixel resolution much better than 1/10th of a pixel. You can find some information for TrackIR cameras here :
http://www.naturalpoint.com/trackir/02- ... rison.html

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