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bulges on 3D Mesh

Once in while when I don’t have sufficient number of images covering a surface the surface gets an ugly bulge in 3d Mesh. No matter how many manual tie points I set on this surface, I cant fix the problem. Often I don’t have a chance to reshoot the scene. Is it a familiar problem? Any workaround?

I wrote in a wrong place.
Please move this topic to the Processing troubleshooting.

Hi Dennis,

The 3D mesh is generated from the densified point cloud, if you have some noise in the densified point cloud it explains why you obtain these bulges.

When you have this effect, you can improve the 3D mesh by editing the point cloud by deleting the points that are noise in the point cloud and that produce this effect. You can do this either by editing manually the densified point cloud:
https://support.pix4d.com/hc/en-us/articles/202560499

Or using the image annotation, this can be especially useful to remove the sky:
https://support.pix4d.com/hc/en-us/articles/202560549

However, it is true that it can be very difficult to remove completely this effect. We keep on working on the algorithms of the 3D mesh to improve it.

Regards,

Big thanks for the answer.
The only solution I found is to shoot more images at the place in question. (this happens only in the places that are not shoot well).
If there was a chance to post a screenshot here, it would help.
I feel that it happens when there is not enough points on the surface and the software doesnt know that it needs to turn the corner. It just trying to guess how to stich the surface. Without clear intersection of surfaces (because one surface has few points) the software softly transfers the dominating surface. That creates bulges.
If there was an algorithm that would find edges (sort of an edge cloud or vector cloud), then these found edges can take priority when the mesh is formed. That will tell software where to turn the corner. I assume finding edges on photos and matching them together is not a science fiction.
Anyway - big thanks for answering.

That will most deffinately add processing time.
Althou that might involve rewriting the core logic of the software -witch migh not be feasible for pix4d.

If after strep 1 or after reoptimizing, you do rematch and optimize, then you will get more automatic tie points and then the model has more points, but if you have for example a lake in the middle of the project, if there are not many automatic tie points, the model will not be able to create more points in the densification, and then the mesh will have big triangles in that area.

You can try as well changing in the processing options, the maximum number of triangles, but this may not have an impact in the affected area.

Hope this help…

but anyway, the mesh creates triangles form the points found, and always place the texture, so it should be completed.

So my I ask what is the correct procedure with the manual tie point?
I’m still not too clear what reoptimize means and what rematch means and when to use it.
So far I was just setting manual tie points and reprocessing the whole step 2.
All I need is a good mesh.
Perhaps I’m missing something.