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Hi Everyone,

I want some advices, I am using optitrack system to track a deformable object (12cm in X, 6cm in Y and 1cm in Z). For the project I have 4 cameras FLEX13.
The distance between cameras and object is between 75 cm (for the farthest ) and 45cm (closest).
Facial markers(3mm) are placed(on three sides of object) on the object in order to get its deformation.
Markers are placed randomly on the object.

My Issue :
1- When object deforms, two markers can see like one.
2- Cameras are not giving deep information.
3- I have a very small working space and want to get very small deformation from my object event when markers movement is less than 1mm.

My Question :
1-Did this cameras positioning is recommended? (What the minimum distance between cameras and tracked object?)
2- Minimum distance between two facial markers in order to be distinguish by cameras?
3- Minimum distance between two cameras?

Sorry for my long message and poor English.

Younes.

Hello Younes,

Thank you for reaching out to the community, and apologies for the delay in any responses.

Your capture project sounds like a tricky one. We usually expect sub-millimeter accuracy from our system around .2mm. Trying to capture movements that are beyond this resolution may be difficult without being able to change the lens on the camera.

There is no minimum required distance between the camera and the object, necessarily, but at least 2 cameras do need to be able to see a marker in order to track it. Having cameras in a line might make it difficult to accurately track the marker position, so if you can vary the angle on the cameras this might help.

Minimum distance between the facial markers also does not have a specific answer. To determine what is required, it would be useful for you to view your markers in Grayscale or Precision mode so you can see the pixels that make up the marker reflection. You will want to make sure that the reflections remain circular, and determine how close the markers can get before their reflections start to merge together. If you cannot clearly see several pixels dividing the two marker reflections, they may be too close.


We may be able to provide you with some more useful information if we are able to look at your data and your setup. If you would like to troubleshoot this further with us, please feel free to open a Support ticket with us at help.naturalpoint.com. Here, you will be able to submit a Take (.tak) for us to look through.

Best regards,
Steven
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Steven Andrews
OptiTrack | Senior Customer Support Engineer