Photoscan non-pro, alignment of cloud methods?

[Mr Whippy]

I was certain in testing that if I aligned my initial camera image (first one in the imported images, or number 1) to be flat that I could then use that as a guide for rotations or corrections of the cloud to be completely accurate.

Ie, in 3DS Max just use the point cloud and rotate the point cloud object say 90deg or whatever to get it aligned properly.

I'm certain I did this with about 3 test reconstructions and assumed it was a good working feature.




But now I'm really struggling to get this behaviour. Quite often it's just one of the random cameras in the set that the scene seems to be aligned with, and it's not easy to get the numerical transformation of that camera from the know camera in the scene.

Using the manual scene rotation feature is just not very useful at all as it's not accurate enough.


Is it possible, or worth adding as a feature, so you can just choose a camera in the list and align the cloud to that camera? You could then easily adjust as necessary with simple transforms (90deg) rather than arbitrary adjustments.


I'll keep having a test as I'm certain this was working before, with camera 1 always being square to the reconstruction.... hmmmmm.


Thanks for any help/advice/thoughts!


Dave

[bigben]

While I don't know the exact method used in Photoscan but it's possible that it's similar to the optimisation of camera positions in panoramic image stitching. Without a fixed reference image, the algorithm can effectively chase it's own tail so to speak because the ony measure of success is the overall closeness of the positions of the matched points. Since you can't actually specify reference points of know positions or the position/orientation of one or more cameras in the standard version then there isn't any information available to orientate the resulting object.  The first thing I do with my sparse point cloud is rotate it to the desired orientation using the standard views.

Most of the objects I've produced end up on their side and I thought that this may have been an optimisation assuming that the primary use was for photogrammetry so that the largest surface was aligned horizontally... but that would just be wild speculation.

[Marcel]

Most of my scans end up upside down, no idea why but it is pretty consistent XD

[chadfx]

Same here, usually upside down. Happy there is the rotate object tool to at least get things oriented better before exporting.

[Mr Whippy]

Well currently I'm loading in Max with Clouds2Max, correcting the alignment, copying the scale/transform/rotation matrix data to CloudCompare, then exporting again.

At least that way I can do things by the numbers, draw rules and levels and double check everything measures up flat/right dimensions etc.


I'll keep having a play with the alignment. I was finding everything was upside down too, and then it struck me it was upside down opposite the last camera reconstructed from... perhaps?!

I'll let you know if I find a consistent way to get alignment squared off to at least one camera... which I'm certain should be possible.


Doing it manually is 'ok', but I still need to fine tune to a level that is really tough without rotation spinners and guides.