Meshing Very Thin Objects

[KBL]

Hello. I've been running into trouble creating an accurate mesh of an airplane as portions of the subject are extremely thin sheet metal. It appears that when the outside and the inside are sufficiently close, a hole is rendered where there should be some small thickness. I've tried a few methods to minimize this issue:

- Generated the mesh based on depth maps as well as the dense cloud (depth maps is more successful)
- Ran the model in 1.71 in addition to several versions of 1.6
- Varied quality and face count settings
- Captured new higher quality data of the problematic area
    - Reprocessed the problematic area with only the new data
    - Reprocessed the problematic area with a combination of new and old data
Reduced the region to enclose only the problematic area and reprocessed using a variety of settings and versions

The best results have been generated on 1.61 or so. Attached are images of the area I'm having trouble with. Any suggestions?

[Alexey Pasumansky]

Hello KBL,

If you have cameras from the both sides of the surface of interest, then the problem could be related to the alignment issues - if the cameras from each side are not positioned (estimated) accurately, the depth data from these two subsets may intersect and form the holes.

In case the image data can be shared with support@agisoft.com, please send the original imagery and the project with the alignment results that you are using, so that we could investigate the problem and try to find the approach to get better result.

[Dano]

Hi, KBL,

try to use this tweak and generate mesh from depth maps one more time:
main/mesh_tvl1

Set it to false.

This tweak is usefull for scanning thin objects.

[KBL]

@Alexey -- I've shared a image set of the problematic area to support@agisoft.com. The area does align fairly well. The full image set is impractically large to share. It's uploading now, but will likely be ready before morning your time.

@Dano -- I haven't heard of that tweak before. I tried to apply it in 1.7.1, but it wasn't recognized. Is this something you're using on the latest version, or old versions only?

[Dano]

You are right. In version 1.7.1 it does not work anymore.
Try to use 1.6.5. It should work.

[RHenriques]

It would be great to have a list off all the available Metashape tweaks and te respective effect.

Best Regards

[Alexey Pasumansky]

try to use this tweak and generate mesh from depth maps one more time:
main/mesh_tvl1

Set it to false.

This tweak is usefull for scanning thin objects.

In the version 1.7.1 it should be BuildModel/tvl1_mesh

[Mak11]

Alexey,

What is the purpose of this tweak?

Mak

[Alexey Pasumansky]

Hello Mak,

This tweak enables the experimental meshing method from 1.4 version, where the depth maps reconstruction has been introduced for the first time.

The method is not optimal and has not been improved since 1.4.x versions, however, it may give good results for very thin surfaces in relatively small projects (for example, wings of the butterfly for marco shooting project).

[KBL]

I've since tried BuildModel/tvl1_mesh, but it was painfully slow and potentially stuck: I waited on 43% complete for 24 hours with no movement. I was worried it was an issue with this dataset in particular, but I've been able to reproduce this issue on other datasets with very thin objects -- they collapse on themselves, despite good texture and lighting on the subjects.

The only thing I've been able to do so far is to mesh again using higher settings. This reduces but does not eliminate the issue. Any further advice would be most welcome. I'm happy to share additional datasets Alexey, if it would be helpful.