FreeTrack Forum

Hello,

I have finally hacked my Quickcam Messenger and I have a working FreeTrack setup. It is great, but I have to say it not completely satisfying, in terms of stability.

When I look forward, it is perfectly stable thanks to the dead zone.
However, when I look on a side, the image is not stable at all, it is constantly oscillating.

In combat sim, it in not that much a problem because you are always moving your head, but in FSX, not being able to have  a stable sideview is a pity.

I tried to look for an explanation, and I got it on the camera view: the center of each led is constantly moving from one position to another, 1 pixel away. In low resolution, this is enough to induce painful oscillations in the head position.

Question: do you experience the same problem? In which resolution are you working?

I noticed that the image from my camera is almost perfectly stable, wheras the cross showing the middle of the led is badly oscillating. I think that the problem come from the way this position is computed. The image is first binarized, the a discrete position is computed for the center of each led.

I have two suggestions for the developpers (I am developper myself):
- An easy one. The center of each led should be computed exactly, as coordinates in real numbers, not as integer. I am almost sure that this is not the case currently, considering that the head oscillate between fixed positions.
- An harder one. Once a led has been located using the binarisation, the center should be computed from the original image (grayscaled), not the binarized one. The binarized image is clearly less stable than the colored image, you can have a look at the "camera" tab of freetrack and compare it with the output of your camera. When you are in a stable position and one pixel at the limit of the led is blinking, it just means that it is "gray" and its color is close to the threshold. Another way to explain it is that the color of the pixel at the limit of the led brings kind of "sub-pixel" information.

I hope this was clear.

I am sure that TrackIR is using this kind of algorithms. I have seen a promotional video suggesting it (I will post it if I find it).

Moving or disappearing center points is usually sign from weak batteries or too big resistor (weak light), wrong model position or dimensions, wrong threshold setting or running outside of leds light angle ...

heres my settings:

Cam MS VX1000 / SFH 485 IR leds

Output size 320 x240
Compression I420
frame rate 30

point diam min 1 max 16

no oscillating, or other "restless" behaviour.... unless i'm running out of batteries or threshold settings are wrong due to weakened battery...


cheers,

Snow