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Author Topic: Point cloud/mesh only covering small area of aligned photos  (Read 1341 times)

ashalota

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Point cloud/mesh only covering small area of aligned photos
« on: March 29, 2021, 08:17:57 PM »
I'm using Metashape 1.6.5

I have 18 photos in a line, partially over water. 14 were aligned (2 at each end did not align).

What's unusual now is that despite all the photos aligning quite well, the output mesh and point clouds seem to only exist under about 5 of the photos.

Here is a screenshot of the situation: https://glihtdata.gsfc.nasa.gov/misc/custom_requests/l0s2_screenshot.png

And the full dataset (500mb) is available here: https://glihtdata.gsfc.nasa.gov/misc/custom_requests/20210329_fl_mesh_too_small.tar.gz

I haven't had this happen before, although usually my data is over dense alpine forests. This seems to be a new issue that is occuring more so over these coastal scenes.

JMR

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Re: Point cloud/mesh only covering small area of aligned photos
« Reply #1 on: March 29, 2021, 08:41:02 PM »
Hi, you need to learn how to use "region". Try to reset region found under Model/transform region or in the region button dropdown.
Kind regards.

If you need some training, I suggest you to take our Agisoft endorsed course. https://accupixel.co.uk/metashape-training-courses/

Geobit & Accupixel

ashalota

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Re: Point cloud/mesh only covering small area of aligned photos
« Reply #2 on: March 29, 2021, 08:50:01 PM »
It did seem related to the region, although now my follow up would be wondering why it had automatically set itself to such a small area.
Usually the program has autodetected the proper region size.

I had to manually resize it, as "reset region" just set it to the abnormally small area.

Alexey Pasumansky

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Re: Point cloud/mesh only covering small area of aligned photos
« Reply #3 on: March 29, 2021, 08:56:06 PM »
Hello ashalota,

I agree with JMR, you should manually resize the bounding box to the area of interest before building dense cloud and completing further processing steps. When building DEM and Mesh I also suggest to use Extrapolated option in the interpolation field in order to create the model without holes extended to the sides of the bounding box.

The default size and orientation of the box depends on the tie points distribution. In your project the box contains about 90% of all tie points, while other points are spread in space without any considerable density.
Best regards,
Alexey Pasumansky,
Agisoft LLC

ashalota

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Re: Point cloud/mesh only covering small area of aligned photos
« Reply #4 on: March 29, 2021, 09:31:35 PM »
That would explain why this issue is only now occurring. My previous datasets had a much more even point distribution.

Do you have any python function you recommend that would let me automatically extend the region bounds to include all of my aligned images?

Alexey Pasumansky

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Re: Point cloud/mesh only covering small area of aligned photos
« Reply #5 on: March 29, 2021, 10:35:01 PM »
Hello ashalota,

If you are not satisfied with the automatic resizeRegion function, you need to modify the size, position and orientation of the box manually, based on your own custom criterion.

Please check the following thread for the simple example that allows to define the bounding box based on its size (width, height, depth), center and rotation angle in XY plane:
https://www.agisoft.com/forum/index.php?topic=13222.msg58670#msg58670
Best regards,
Alexey Pasumansky,
Agisoft LLC