Having trouble aligning cameras properly in RC and Photoscan

(Abby Crawford) #1

A couple of weeks ago I photographed a book cart for the local museum. Each side of the cart has different books on it, and the handles of the cart each have all sorts of different yarn around them making them unique. The problem that I am running into is that the photos from one end of the cart aren’t aligning properly, perhaps because there’s the same infographic on both ends of the cart (see image below). So the photos from one end align with the photos from the other end. I would think that the books and yarn would be enough to help the photos align, but I guess not.

Anyway, I’ve tried adding control points to the cart and the items on the cart, but that didn’t make much difference. I’ve tried running the photo set in Reality Capture and Photoscan, with similar alignment results in both. I’ve gotten the mesh to turn out semi-ok, but the alignment problems are creating texture issues.

Does anybody have any clever suggestions for how to get everything to align correctly?

(Nebulousflynn) #2

hey @abbyec - did you try aligning the two ends as separate chunks in PhotoScan then merging?

Did you use any image masking? Just thinking that the BG might also be causing an issue with misalignment. Perhaps re photographing (if possible) with unique targets on the ground around the trolley might help?

(Arc 3 D) #3

Yes, sometimes masking will help and definitely re-shooting with unique off-subject targets can help. However, alignment problems are hard to solve with multiple chunks and I’ve found staying with one chunk often works better. You said you get a “semi-ok” mesh. Thus you must have an initial alignment solution for a significant fraction of the photos. If you look at the pattern of the aligned cameras, sometimes you can see some that are obviously in the wrong place (based on your knowledge of how you shot things). You should “reset alignment” (using photoscan terminology) for all those photos and then “realign” those photos. This will often shake those photos into the right positions. Sometimes it requires a few “reset-realign” cycles to get things to come out right. Also try a “realign” for the photos that didn’t initially align; sometimes this also works. Finally don’t forget to “optimize cameras” to tweak the last bit of accuracy into the alignment.

(Michal Zurawski) #4

Too big “base” distance or poorly focused photos. You should take more photos at the corner of the shelf. Background usually is not the issue if you have good quality imput. Think about using smaller apperture for better DOF. Situation when you have two or three photos that are destroying your aligment is also possible. Basically it is about imput data. If you can’t retake photos you can do something else. Separate photos in series, and then try to align. If you are satisfied with mesh you can always turn off some cameras in texture generation process. when you will identifie causing problems cameras, just delete them and realign whole set.