Warsaw University try on ARSandbox

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  • #101972
    GeoKicak
    Participant

    Hello everybody 🙂

    Here, at Warsaw University (faculty of Geology) we heard about this marvelous Augmented Reality Sandbox project and have come up with a small group of admirers (3) of implementing this idea on polish ground.
    We ( Łukasz Królik, Radosław Staniszewski and other people of kind heart) have been working to set up this installation full running. Unfortunately without popper funds and materials we were not been able to acquire a PC/Laptop capable of running the program to its fullest (no nVidia card = no water simulation for us T_T ). For this problem we came up with a idea™ to fill one of the pools in our building with sand and use real water instead 😀

    Here are the results:
    Photos:
    Building a station for the projector.
    Building a station for the projector.
    Setup calibration.
    Setup calibration.
    It works 😀 Radek and his happy little helper.
    It works :D Radek and his happy little helper.


    Erosion test.
    Erosion test.
    Erosion again.
    Erosion again.
    Erosion contemplation.
    Erosion contemplation.
    Even deeper contemplation.
    Even deeper contemplation.
    Sudden enlightenment!
    Sudden enlightenment!


    River delta simulation.
    River delta simulation.
    Delta zoom.
    Delta zoom.
    Delta zoom 2.
    Delta zoom 2.
    Delta once more.
    Delta once more.
    Found the scale tool.
    Found the scale tool.

    Thees and more photos available at:
    https://www.facebook.com/media/set/?set=a.1000366133391578&type=1&l=3bf2ade087

    Video:

    Using real water instead of a simulated one enabled new possibilities to observe better such processes like the propagation of river (in a smaller scale) delta or erosion and accumulation processes.

    Results could be better if we actually bother to measure the distance between the kinect, sand and the projector and took more than one cycle of calibration. We also know that we messed up with the resolution of the projector because laptop had imposed 1920×1080 over the native 1600×1200 for our projector (we could have a wider simulation).

    However the most concerning problem we are currently facing are those level inconsistencies.
    Suspect:

    Halp


    I don’t know is this our fault (sloppy calibration and lack of any calculations for hardware mounting.
    So I ask for your help in the elimination of this problem.
    Pretty please 🙂 ?

    • This topic was modified 4 years, 8 months ago by GeoKicak.
    • This topic was modified 4 years, 8 months ago by GeoKicak.
    • This topic was modified 4 years, 8 months ago by GeoKicak.
    • This topic was modified 4 years, 8 months ago by GeoKicak.
    • This topic was modified 4 years, 8 months ago by GeoKicak.
    • This topic was modified 4 years, 8 months ago by GeoKicak.
    • This topic was modified 4 years, 8 months ago by GeoKicak.
    #102010
    matthias
    Participant

    see this thread:
    http://lakeviz.org/forums/topic/weird-pattern/

    i have the same issue, and never got an answer whether internal calibration would make a difference. but it seems like you will have to live with these inconsistencies.

    #102024
    Oliver Kreylos
    Keymaster

    Cool idea!

    Unfortunately, the stepping problem you are seeing is something some Kinects do. It’s a flaw of the device hardware itself, and it cannot be fixed via calibration. If you have access to another Kinect camera, please try that one to see if it works better.

    What makes the problem worse in your case is the long distance between the Kinect and the surface you are scanning (looks to be about 2 meters?). That’s outside the Kinect’s accurate scanning range; the ideal resolution of its elevation measurements at that distance will be > 1 centimeter, and noise will be on the order of several centimeters.

    #102042
    GeoKicak
    Participant

    Aha!

    Thank you very much for identifying what causes this stepping problem.
    The kinect is suspended at approximately 2,5 meters so yes we know, it is mounted not at the recommended height.

    After 15 minutes of TORCH searching all of the interwebz in an effort to find some solution to this behavior I have found only more information about the probable cause of the stepping problem.

    The technology was developed by PrimeSense which is now owned by Apple. Details about that technology are not publicly available and the only legal way to get some info about it is through reviewing the patent applications.

    Some time later …

    So, from these documents it seems kinekt depth map is constructed by analyzing a speckle pattern of the infrared laser light which in basic is an analyzing technique of a known pattern called structured light.

    This kindergarten method
    (http://www.handimania.com/uploads/3d-handprint-12.jpg)
    elevated by human ingenuity, machines & electronics
    (http://homes.cs.washington.edu/~curless/images/hand_first_pattern.jpg)
    (http://www.laserfocusworld.com/content/dam/etc/medialib/new-lib/laser-focus-world/online-articles/2011/01/93355.res/_jcr_content/renditions/pennwell.web.390.296.gif)
    to obey our hearts desires was further improved in kinect, which uses the aforementioned speckle pattern (http://gmv.cast.uark.edu/wp-content/uploads/2012/07/KinectIR.png).

    From my personal experience in the meaner of dots they do have a tendency to act funky and produce interference in form of moving phantom objects (eg. circles or lines at 5:03 –> https://www.youtube.com/watch?v=QAja2jp1VjE ) but these wall like interferences require 2 shifted superimposed images to be visible.

    Kinect analyzes the shift of those speckles between the IR feed and the initial pattern stored in memory, then calculates the difference in the pattern dot shift at different distances and on the basis of triangulation principle calculates the depth of an object
    (http://www.futurepicture.org/?p=97)
    (http://www.depthbiomechanics.co.uk/?p=100).

    The important part (Me thinks so) it that the fixed dot pastern is semi-random.
    (http://www.francescocastaldo.org/tutorials/kinect.pdf)

    Since silicates are known to reflect IR and other mineral grains in snad might absorb some of it
    (http://articles.adsabs.harvard.edu//full/1994MNRAS.269.1011K/0001011.000.html) maybe it is possible that the anchor’s shift

    (https://courses.engr.illinois.edu/cs498dh/fa2011/lectures/Lecture%2025%20-%20How%20the%20Kinect%20Works%20-%20CP%20Fall%202011.pdf)
    can produce a Moiré pattern appearing as moving, stepping walls derived from square IR pixels.

    Moire pattern

    some more searching …

    But then again I know nothing of optics and I am not a smart man, and so I am maybe totally wrong and this error has been reported in various places on earth for all devices that use Primesense chips (Kinect, Asus Xtion, Asus Xtion Pro, and Primesense camera) and the solution for kinect is to use libfreenect and modify SensorKinect\Data\GlobalDefaultsKinect.ini file and uncomment
    ;GMCMode=0
    so it states
    GMCMode=0
    like it is written here https://github.com/OpenNI/OpenNI2/issues/81

    I should definitely go sleep now,

    Bye, Have a nice day 😀

    • This reply was modified 4 years, 7 months ago by GeoKicak.
    • This reply was modified 4 years, 7 months ago by GeoKicak.
    • This reply was modified 4 years, 7 months ago by GeoKicak.
    • This reply was modified 4 years, 7 months ago by GeoKicak.
    #102070
    GeoKicak
    Participant

    ok, after searching the internet I found several other ways of hardware error correction by using software methods.
    One of them was published in paper in 2013 by Centre for Sports Engineering Research, Sheffield Hallam University:

    http://www.depthbiomechanics.co.uk/wp-content/uploads/downloads/2014/01/FINAL-3D-Body-Scanning-Paper-2013-checked.pdf

    The IR depth scan results after that calibration were dramatically improved.
    This makes me wonder, is it possible to integrate a similar error correcting script or daemon to work of this problem in ARSandbox?

    • This reply was modified 4 years, 7 months ago by GeoKicak.
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