No map, just scattered pixels that migrate

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    When I run the sandbox with the -uhm and -fpv command line options, I do not see a depth map projected, instead only a collection of pixels scattered around the sandbox. They do appear to be color coded by height, but they start fairly evenly scattered and then slowly appear and disappear in a way that starts to show the hills of the sand but eventually even those peaks of collected pixels disappear and I’m left with just a blank display.

    During the calibration, I did have to manually make some edits to the BoxLayout.txt file, flipping a few signs to make the green blob mimic the target movements (it was reversed left/right) and making the z’s all negative (base plane was positive).

    Do these manual updates that I had to make suggest that I should be using a different Kinect camera or that there is something awry with the camera settings that would make me only see scattered pixels and have them slowly transform (despite no changes in the sand surface) from a roughly even dispersion across the sand to a representative collection of colored pixels on the hills to completely gone?

    Any help would be greatly appreciated!

    Sean Robinson

    Some more information may help… What model Kinect (hardware)? What versions of Vrui, Kinect (software), and SARndbox?

    I suspect you are seeing the underside of the projected terrain. If you click and drag (using left mouse button) in the SARndbox window on the sand, can you flip the terrain so you are seeing solid colors and not just isolated pixels?

    If you have a Kinect V2, you probably want to upgrade per Oliver’s recent announcement. If you are using a Kinect V1 or SARndbox v2.8, keep reading.

    The green disc moving in the wrong direction means the Kinect (hardware) is mounted upside-down to what CalibrateProjector expects. CalibrateProjector starts with the numbers in BoxLayout.txt. If those values do not match your physical setup because you manually edited them, CalibrateProjector (and later, SARndbox) will be confused about directions and boundaries.

    My suggestion is to repeat Step 8 and leave the signs as they are. Repeat Step 9 and ignore the location of the projected circle, just use the color. Center the target on the white crosshairs and capture when the circle turns green (even if the projected circle is not near the target). After Step 9, the projected circle should closely follow the physical circle.

    Oliver Kreylos

    It sounds like you are using a second-generation Kinect (Kinect-for-Xbox-One). If that’s the case, you need to update to the newest software versions where I fixed some Kinect V2-related issues.

    Afterwards, you need to pass some special parameters to the SARndbox software because the Kinect V1 and V2 are quite different. Specifically, you need to loosen the frame filter parameters via -sp 10 2. The 2 value is appropriate for Kinect V1; you will have to experiment with larger values such as 5 or even 10 until you get a solid terrain model and not too much noise.


    Yes, we have a Kinect v2 (bigger, boxier, one camera lens on the left). I think I had tried 2.8 (but maybe that initial install was before the 2.8 release, time is really weird these days!) when we tried Ubuntu 20.10, but ran into issues with a TIFF library not being where the software expected it to be (and a symbolic link didn’t solve it), so I reverted to Ubuntu 18.04 and 2.7 was the install that the script put in place there. Should I update 18.04 to something more recent (20.04 LTS?) and then update to 2.8 or can I leave 18.04 in place and just do the 2.8 update? And, as far as running that update to 2.8, is it as easy as running the script or do I need to do anything special to force 2.8 over our current 2.7?


    Our sandbox is in a middle school science classroom and the post that holds the projector and camera make it too wide to fit through the doorway, so I’m only able to work on the sandbox on Wednesdays when, because of our hybrid teaching model due to covid, there aren’t any kids in the classroom. Just ran the build script to update to Vrui 8, Kinect 3.10, and SARndbox 2.8. Have a few parent conferences to do today, but will finish off the rest of the recalibration/etc this afternoon and hopefully we’ll be good to go! Will update later today, thanks for the help so far!


    We’re golden! The update to all three pieces of software did the trick and the Kinect produced appropriate depth plane equation and corner locations, so calibrating was a breeze. I did include -sp 10 10 in my RunSARndbox script which definitely helped smooth out the topo lines and made for smoother redraws as features of the surface were updated. I also adapted the Desktop shortcut to make a second shortcut for CalibrateProjector, just in case the projector gets bumped (middle schoolers) or when/if the pole is removed and replaced to get it through the doorway. This should make it easier for the classroom teacher to run that calibration without having to do anything in the terminal.

    Thanks for all the help!

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