TL;DR at the end
So I’ve mostly been testing the Pop2 since I got it a couple months ago, and I’m working on something I can post to the showcase thread. My main interest in the scanner was using it to scan figurine sized objects, so generally not over 15in/38cm. I’ve been able to extract some very good details out of the one I plan on posting eventually, but it is a difficult scan. Its a mostly PVC figurine that was painted using dark shades of red, blue and black, and has some highlights of canvas tan. Needless to say IR does not play nice with dark colors when scanning, so it has posed some difficulty with tracking or even scanning in general.
I’ve just started playing with an idea today that has shown some promise. Using marker tracking mode works great for the hard to scan objects, but the problem is getting enough markers in the frame around certain parts of a figurine without putting stickers directly onto the figure, which for some features just doesn’t work well. Like trying to scan under an overhanging feature where there is only enough room to fit maybe 3/4 of one sticker, and the angle of the scanner is such that it will miss most other markers in the area. That got me to thinking about how the markers are tracked. Now without looking into the program logic RevoPoint uses I cannot confirm how it is programmed, but for the fastest and most reliable processing it needs to look for a static shape and the ease of detecting that shape is determined by contrast. At least in the machine vision systems I’ve worked with. The stickers provide a white dot inside of a black circle, a high contrast target, but the camera is only looking for the white circle, not the black ring. That train of thought lead me down a rabbit hole and I emerged from the other side with an almost perfect solution.
To be specific, ball head sewing needles, the ones with a colored ball on the end.
I got my sewing supplies and grabbed a tin of these needles with white balls. I stuck some of the Blu Tack that came with the scanner onto various spots of the figurine I’ve got set up, poked a bunch of needles through it so the white balls are all around the target area.
Sure enough the scanner tracks the needles like the marker stickers. The ones I’ve got on hand only have a 3-3.5mm ball on them, the tracking has the same issue you can get when at an angle to the stickers and they don’t reflect well (even though the balls reflect very well), I’m hoping it can be made better with larger balls. I’ve ordered some pins with a 6.5mm ball to test if they work better and should be able to update you before long.
One of the great things about this is that the scanner does not pick up reflective metal hardly at all, so the needle part isn’t visible to the scanner. Keep in mind that while the needle portion does not get picked up by the scanner, it will still block the projected light used to scan your object, so placement will effect how well it scans. Lots of needles in front of the object mean lots obstruction in the scan path. You can see the shadows they cause in the black and white image, so be mindful of placement.
I did also test changing the background and noticed that when putting white paper behind my target it had more issues with detecting the pin heads.
Two more great points in favor of this, ball head needles can be picked up for relatively cheap (100 pack of 6.5mm ball with 65mm shaft for 5 USD) and can be reused indefinitely.
White, and possibly pearlized ball head needles can be used under the marker tracking mode instead of the stickers.
Use some tack, putty, or whatever you have on hand to stick the needles around the target so there are plenty visible at every angle/side you are going to scan.
The metal of the needle is not picked up by the POP2, but still blocks light used to scan, be mindful of placement.
May not work well against white backgrounds.
If anyone has the supplies on hand, please go ahead and try it and let us know how it works for you.
P.S. Anytime you’re pushing needles through something, please be careful not to stab yourself.