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Author Topic: butterfly Mesh Full Of Holes  (Read 3184 times)

underthesun

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butterfly Mesh Full Of Holes
« on: December 13, 2021, 05:58:08 AM »
Hello, 

I am working on a personal project and I am new to photogrammetry.
 
I am trying to create a 3d mesh from a butterfly, I am using the item on a turn table and masking a “background” photo from each viewing angle. Photo alignment is working great.
 
I am using a nikon D90 with a fixed 50mm lens on a tripod with a remote, subject has a large white background behind it and is well lit. I am using a low ISO and a high fstop. I have shot in RAW and jpeg with very little difference in the result.
 
I have been digging through the manual and forums trying to come up with an answer as to why my mesh is absolutely filled with holes. 

I came across a forum post that suggesting “buildMode/tvl_mesh”  for thin objects, This looks like a command prompt command or something but I am not finding a reference to a command line input in the user manual. 

I also came across this article https://www.agisoft.com/index.php?id=48 that does exactly what I would like to do but the same options / setting don’t appear anymore in agisoft. I guess I am on a different software version. 
 
the manual says that shiny or thin subjects are problematic for metashape and this defiantly falls under the thin category. 
 
I have also tried filling the holes after the fact with options in the “tools – mesh” menus but that does not seem to do much.
 
I have sunk more time into this then I really have time to do and need some help.

I would be happy to share my data set and file if anyone is interested in taking a look.

Thanks

Corensia

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Re: butterfly Mesh Full Of Holes
« Reply #1 on: December 13, 2021, 07:18:47 AM »
I'd like to take a shot at it if you would be willing to share the data.

Also if you haven't tried it yet, I would try generating the mesh from depth maps.

underthesun

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Re: butterfly Mesh Full Of Holes
« Reply #2 on: December 14, 2021, 05:21:31 AM »
OK thanks!

yes I have tried generating the mesh from depth maps ultra high quality with no filtering and various stages of other options aswell.

I will PM you a link to the files they are to large to u[load here.

James

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Re: butterfly Mesh Full Of Holes
« Reply #3 on: December 15, 2021, 03:30:24 PM »
I would suggest to duplicate your chunk, and disable photos of the 'top' surface in one chunk, and bottom surface in the other chunk, then build mesh in each chunk (you shouldn't get any holes that way) and then enable the 'show aligned chunks' button to overlay the two meshes and check for any intersections between top and bottom, which could be the result of slight misalignment of images or to do with translucency of the wings (i.e. maybe you are actually reconstructing the subsurface!?). Any intersections would cause Metashape to decide a hole was preferable to an inside out intersecting mesh (I guess).

I'm not sure if 'show aligned chunks' will work if the chunks are only duplicated and not explicitly 'aligned', but you can align them without causing any change in their actual alignments by using the align chunks tool, and aligning 'by cameras' which will be identical since you duplicated the chunk.

Feel free to send me a link too as I do enjoy playing!

underthesun

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Re: butterfly Mesh Full Of Holes
« Reply #4 on: December 15, 2021, 03:49:00 PM »
James,

link incoming!

thanks for the suggestion, Ill give it a try when I can free up my pc for some processing time.


Alexey Pasumansky

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Re: butterfly Mesh Full Of Holes
« Reply #5 on: January 28, 2022, 07:26:21 PM »
Hello,

We have just published the article that may be helpful, when working with such thin surfaces:
https://agisoft.freshdesk.com/a/solutions/articles/31000163220

The approach assumes adding two tweaks via Advanced Preferences tab prior to the mesh from the depth maps generation:
Code: [Select]
BuildModel/ooc_surface_blow_up = 0.95
BuildModel/ooc_surface_blow_off = 0.95

After using these tweaks do not forget to disable them (set to zero value) or remove from the tweaks list, in order to not have further projects affected, when it wasn't necessary.
Best regards,
Alexey Pasumansky,
Agisoft LLC

jenkinsm

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Re: butterfly Mesh Full Of Holes
« Reply #6 on: March 30, 2022, 12:35:22 AM »
Hi Alexey,

I captured an object that is quite fat in some areas but very thin in others. The normal depth maps method results in a hole in the thin area and some missing mesh around the thin edges, but enabling this tweak dramatically affects the mesh quality overall so it's not a viable solution for me.

Do you have any tips on how to handle a situation like this?

Thanks!

Hello,

We have just published the article that may be helpful, when working with such thin surfaces:
https://agisoft.freshdesk.com/a/solutions/articles/31000163220

The approach assumes adding two tweaks via Advanced Preferences tab prior to the mesh from the depth maps generation:
Code: [Select]
BuildModel/ooc_surface_blow_up = 0.95
BuildModel/ooc_surface_blow_off = 0.95

After using these tweaks do not forget to disable them (set to zero value) or remove from the tweaks list, in order to not have further projects affected, when it wasn't necessary.