Nice and very unusual project. I like your setup with the branch fixed to the rotation table, I wonder how many “what are you doing in there” you got so far!
My experience is with very low quality data and really not optimum conditions, so I guess it can be easily improved.
Tiny branches (lavender)
I used a low quality USB microscope, one angle to the base and 40-50 images. The “setup” picture is in the commentary section. The light was very bad (from USB LED) and no background control expect for a piece of paper (lot of reflective stuff behind that paper…). The scanning is less than a minute and processing less than 10. The image are like 2MP so it goes fast. The quality or even the focus did not impact much the result, it does impact the texture. But there are enough feature at the end to get camera positions.
Video of penzai
This other test of small tree was recorded in a garden in Suzhou, China. It was in summer so very sunny weather. The “white dot” on top of the point cloud are actually saturation of the sensor due to the light, not snow. Shot in 1080p while walking around the object (20-30s). Position of the branch came out ok but way too much saturation and lot of leaves “hide” the trunk. Again very low resolution image, very fast processing and it works “on site”.
In terms of “personal opinion on expensive technique that I don’t have”. I think handling scanner or LIDAR might not be practical as you will have to “reach out” to get all the details, looking all side of the branch. These are good instrument, but not meant for such small things. Plus once you get out of the lab, if that’s a consideration, you will be stuck.
Depending the level of accuracy you need, you might consider a customize setup that fit well “branches”, like a circle of cameras or something. SFM is indeed slower, but the cameras give you more flexibility in the setup.
Also you can record other data from simple camera. There are package for structured light (at least for research) if you want to try.
You can also use “linear laser”. It’s closer to “structured light” than “lidar” as it records how the laser beam in your image moves according to the distance between camera and object. Hence resolution depend greatly on camera accuracy. But it costs nothing.