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Author Topic: Top-Bottom Merge  (Read 257 times)

temetofi

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Top-Bottom Merge
« on: May 16, 2022, 07:44:46 AM »
As part of a project, we want to create a 3D model from images.

We took pictures of the top of an object, imported them in a chunk, created masks and aligned them. The same procedure was used for the bottom of the object. Then at least 3 identical points were searched for in both chunks (identical points were given the same name in both chunks). Then we set scale bars in both chunks. In the next step we wanted to merge the two chunks (+ markers). Unfortunately, merging the top and bottom does not always work. Can you help us with this?

Thanks in advance!

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« Last Edit: May 18, 2022, 02:23:14 PM by temetofi »

Alexey Pasumansky

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Re: Top-Bottom Merge
« Reply #1 on: May 16, 2022, 02:12:34 PM »
Hello temetofi,

I would suggest to check the following tutorials related to complete model reconstruction:
https://agisoft.freshdesk.com/support/solutions/articles/31000163388-automatic-masking-from-the-model
https://agisoft.freshdesk.com/support/solutions/articles/31000163268-turntable-capturing-scenario-and-processing-workflow

You should provide sufficient overlap, however, between the image sub-sets for more accurate processing results (for higher accuracy it is suggested to align all the images in the single chunk).
Best regards,
Alexey Pasumansky,
Agisoft LLC

nik_ska

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Re: Top-Bottom Merge
« Reply #2 on: May 18, 2022, 10:44:48 AM »
In my experience of scanning small figurines (https://sketchfab.com/nikska/collections/sailor-figurines), the top and bottom chunks may not correctly merge or be aligned do to the optics used and possible focus breathing.
I found it ideal to try and keep the constant distance from the object center for both chunks and avoid smaller focus distances for macro lens.
Another issue is the lighting mismatch for both chunks, but this results mostly in an uneven texture rather than incorrect model.

So, as a rule of thumb, after an incorrect merge, I was making a full new run with the fixed focus trying to reposition camera rather than changing the focus. Also make sure you are using prime lens, this eliminates even the slightest probability of changing optics geometry.