Camera Tracker question about "Max Delta"

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Camera Tracker question about "Max Delta"

Postby chrisr » Tue Jul 05, 2016 5:56 pm

Good morning / afternoon all!
I have a quick question on the Max Delta adjustment in the camera tracker. I couldn't find any direct information for the Camera Tracker and Max Delta adjustment, but for the Air Scan there is the info that the Max Delta function determines the maximum speed for Multi touch Point Tracking. Will this be the same within the Camera Tracker?

Or another guess would be, that maybe it means the maximum distance (Manhattan distance) in units (pixels?) that will be reported between consecutive point positions? Which could be the same thing. It is referenced in the AirScan, as "speed" so is this reported in time as in 100 milliseconds?

Thanks for any Input. You guys always share some great insight, its always appreciated.

Have a great week.
Thank You

ChrisR
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Re: Camera Tracker question about "Max Delta"

Postby malkuth23 » Wed Jul 06, 2016 9:09 am

Delta is basically speed (distance/time)

Max delta refers to the same thing in Airscan and in Camera tracker... Basically, it is saying that if the point moves too fast then don't use it. This is useful if you are having some bad data and points are hopping around.

Is this the answer you were looking for?
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Re: Camera Tracker question about "Max Delta"

Postby chrisr » Wed Jul 06, 2016 2:25 pm

Great! Thanks! Just wanted to clarify, I just wasn't sure.

Thanks again malkuth!
Thank You

ChrisR
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Re: Camera Tracker question about "Max Delta"

Postby malkuth23 » Thu Jul 07, 2016 9:55 am

I mean... I hope I am telling the truth. This is always how I have used that feature and I am pretty sure I am right :/

Please anyone correct me if I am wrong.
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Re: Camera Tracker question about "Max Delta"

Postby Dennis Kuypers » Fri Jul 08, 2016 2:41 pm

Hi,

mathematically speaking a delta is the difference between two values so 'old_position' - 'new_position' which also happens to be the distance/time or also known as speed. That means that max delta is the maximum speed, or the maximum amount of units a point is allowed to move. This helps the algorithm to detect points.

One example: The Tracker gets these two images where "X" is a point that was found and "O" is just empty space:

Code: Select all
OOOOOOO
OXOOOOO
OOOOOOO

Code: Select all
OOOOOOO
OOOOOXO
OOOOOOO


note how the X has moved by 4 units. The max delta helps us to identify the two cases that are possible:

A) The X has moved by 4 units
B) the X has disappeared and there is a different point that happens to have appeared in the same moment, just 4 units away

A max delta set to 10 would make the tracker conclude that case A is true. A max delta of 2 would rule out case A and the system would decide that the X in the second pixture is a different one and case B would be the truth,

Same applies to ID Tag Tracking.

Regards
Dennis
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