Imported mesh gets wrong alignment/coordinates

[Opparg]

I keep running into a bug where I work with the mesh in an external program, and even though nothing has changed as far as the other program goes (Wings3d, Blender, 3Dcoat etc), when I reimport, it sometimes appears out of alignment with the pointcloud.. The only way to fix it, is to reload the last save where it was in alignment, export it again, and continue working.

It -seems- to happen most often when I have just saved the Photoscan file or done an operation in Photoscan and then saved.

Is this a known issue anyone is aware of, and any workarounds? It seems almost completely random.

Thanks!

[Alexey Pasumansky]

Hello Opparg,

If you are using PhotoScan Professional, is the any coordinates applied to the model (any data in the Reference pane)?

[Opparg]

I am using the Standard edition. Is there any way to see it there?

[Alexey Pasumansky]

Hello Opparg,

In Standard edition the coordinates cannot be applied, so it shouldn't be the case.

Can you reproduce the issue with the unmodified model exported from PhotoScan and imported back? Also have you tried to open both modified and original (exported from PhotoScan) models in the model editing applications that you are using - do they align properly?

[Opparg]

I have tried but can't reproduce it with an unmodified version of the mesh so far. It only happens 1/30 or so with a modified mesh, and even with different kinds of software.

I export the model for cleanup, steps of retopology etc. When I import it, most of the time it aligns correctly. But sometimes it comes out of alignment, how much, seems completely random. Rotation and location can be slightly, or completely off, but scaling is always the same.

Sometimes, when I reload the project file and try importing again, it aligns correctly, sometimes it doesn't. Then all I can do is to export the mesh I currently have in the project and continue working (which is a reason I save often)  Sometimes, I can reimport an older version of the exported mesh, but at other times, they are -all- out of alignment, except for the one already in the project file.

[Alexey Pasumansky]

Hello Opparg,

Is it possible that you are using Rotate Object tool in PhotoScan after exporting mesh and before importing it back?

Another likely reason is orientation modification in the external application, for example, if the  external application is using other coordinate system convention for import/export (for example, Y-up instead of Z-up).

[Opparg]

Hmm... Ok, I tried exporting, rotating and importing, and -sometimes- it comes back out of alignment, but not always.  How does this tool actually work?  The manual only says it rotates the object but it looks like it just rotates the camera, since I don't have any reference to compare it with.  Is it possible to just rotate the camera and not the actual object?

[Alexey Pasumansky]

Hello Opparg,

When Rotate Object tool is turned on the orientation of the coordinate system axis (in the bottom right corner of the Model view) is fixed, so it allows to change the orientation of the model in the coordinate system space. Whereas using regular rotation - changes the viewpoint orientation, while the orientation of the model in the coordinate system space is not affected.

[Opparg]

Ok now I can see it clearly! What I thought was a bug was my confusion between the navigation tool and the object rotation tool. 

Thank you so much for the help, and sorry for the inconvenience!