I’d worked on a project a few years back that had a built in photogrammetry rig consisting of 29 Ras-Pi’s set up in a photobooth. For that project, we needed to make a calibration object that could be placed inside of the booth at a fixed point should the cameras move over time and need to be re-registered.
One of the tricky things about this setup though is that each camera needed to see something unique within the frame that the software could register the overlapping unique areas within the booth to start registering where certain cameras were in relation to one another. Problem was that the booth had been designed for humans and as such was smooth white, featureless, and futuristic. Not too many unique visual identifiers in a space that looks like a surgical arena.
As such, we had to make a skin for the calibration object itself that would be bright to be definitely seen by all the cameras and non-repeating. At first we tried busy fabrics, which were a promising lead but ultimately didn’t work. The nature of mass produced fabrics is that they use a pattern for their designs, which ended up causing areas of repetition across the surface of the cloth as the pattern repeated. Next up we tried adorning an object covered in a busy fabric with distinguishing visual items, such as tape and folds in certain areas. This worked better but our calibration was still miss registering areas of fabric to similar areas. In the end we decided to make our own print.
This proved to be more difficult then imagined, and ended up taking 3 tries.
1st pass was me trying to make a program that would export a grid of randomly shaded cells, which again ended up confusing our calibration software. I ended up slapping on a few letters to serve as randomized decals which ended up looking like so…
But, it didn’t take.
Next up was going in and manually randomizing it using oddball strokes and a semi-random background. that option promising…
But ended up not working that well either. My guess was the lack of contrast between the background and the randomized strokes, so I decided to go all out with it…
This was the version that ended up doing it. Not a square inch on it that was repeating, super high contrast, and pleasant on the eyes to boot.
Anyways, have fun with it, I know I did making it.
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