How to scan rotating object or person?


#1

Hi,
We are developing an application that creates 3D models of a human head. We are using Structure Sensor, the latest SDK and our implementation is based on the code provided in the Scanner sample.
The problem is that our customers usually will not have much space to go around a person that is being scanned. So we need to give them an option to hold still an iPad with a sensor while scanning and have the scanned person to rotate slowly 360 degrees (e.g. rotating in the turning computer chair).
However, in this case Tracker quickly loses the tracking and the resultant model comes out totally distorted. Both applications - ours and the Scanner sample - exhibit this behavior.
So, the question is this - is there any way to get a model of decent quality (i.e. without Tracker losing track) when the person that is being scanned is slowly rotating in place and the person who holds the iPad stands still?

Thank you.


#2

@irenac,

Could you try maybe four positions instead of continuous movement?

-Jim


#3

Thank you, Jim.
We will definitely try that right away.

Ok, tried this but unfortunately this didn’t work either. Here are the screenshots of good (going around with iPad) and bad (holding iPad still and turning the table with the head) result models just to illustrate what I am talking about.

Both models are scanned using Scanner sample app from the latest SDK.

Is there any setup for STTracker and STMapper that could help in getting a decent model when object being scanned is turning around instead of iPad moving around the object? The sample application is probably using all the basic functionality but maybe there are some hidden gems that are not demonstrated by the sample app but could really help us in this situation? Please help us here!

Thank you.


#4

I get the same models by turning a chair. I bought a Ladysuzan like aparatus from china able to support the weight of a person and making it move by a arduino cnc controlled. Not finished yet but the iPad would be fixed and the person could have a handstand to gab. Problem would be for the person to stay put.


#5

Hi Jean Pierre,
Thanks for giving your input to this problem. Probably I am missing something but I don’t understand how rotating a person on ladysusan is different from rotating him in a turning chair with iPad in fixed position in both cases? Thanks.


#6

I think what @jipilabont said about keeping the person still during rotation will be the main problem.

I just tried the experiment, and it’s very difficult for the subject to keep their head / neck from moving relative to their shoulders / chest. The scanning cube was probably set large enough to pick up some of the chest, because otherwise the nose tends to be cut off. Since the tracking is currently best at rigid bodies, a distortion is introduced.

You might try setting the cube at a fixed location per SDK 0.6 Fix the Cube at a certain distance from the user

This will allow the cube to be only large enough to enclose the head. Of course, the face and ears are not stone, so there will still be the possibility of movement.

-Jim


#7

I tested with seating in a chair and the problem was to get the z axis in the center of the person. My strategy is to make stand the person over th “X” on the ladysuzan(the z axis), and having a center post offset of 6 inches from that axis tto grab to with the hands.