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Author Topic: Odd stair stepping effect from export  (Read 1573 times)

ahuczekdesign

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Odd stair stepping effect from export
« on: September 17, 2020, 01:59:17 AM »
Hi everyone,

New to photogrammetry and I'm working on my first project. I am recreating a chess piece for a friend to 3d print and so far from the support pages here I've got a great mesh to work with that I'm happy with. The only problem is when I open my file in Meshmixer the model has aggressive "steps" to it. I've attached a couple screen grabs to show what I mean. You can see my mesh in Metashape and then my imported .obj in Meshmixer.  The only thing that was outside of the norm and required further research was I initially had a rough spot on my mesh from about 120 photos so I retook about 25 images from a new angle and added a new "chunk" in metashape and merged them. I recalculated and remeshed and the results are great but something isn't right when I save it out I guess.

Any help here would be great! I'm just not sure what I'm doing wrong.

Alexey Pasumansky

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Re: Odd stair stepping effect from export
« Reply #1 on: September 17, 2020, 01:33:09 PM »
Hello ahuczekdesign,

Was the model referenced in Metashape project? If so, what was the magnitude of X, Y coordinates and which coordinate system has been used?

Such behavior is usually observed, when the coordinates of the model vertices are too large (like tens of millions of meters) and the full values cannot be properly treated by the external applications, which are using float format to store the coordinate values.
In such case you can use Shift fields for X and Y coordinates on export to subtract large base values from the corresponding coordinates and leave only hundreds or thousands meters instead of millions.
Best regards,
Alexey Pasumansky,
Agisoft LLC

ahuczekdesign

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Re: Odd stair stepping effect from export
« Reply #2 on: September 17, 2020, 04:24:03 PM »
Hi Alexey. Thanks for the response.

I'm not sure what you mean when you ask if the model was referenced in Metashape? Do you mean did I resize it? I did not if that's what you're asking. I simply added my photos and then went through the workflow menu.

How would I shift the fields of X and Y coordinates?

Alexey Pasumansky

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Re: Odd stair stepping effect from export
« Reply #3 on: September 17, 2020, 05:01:13 PM »
Hello ahuczekdesign,

According to the screenshot, you are working with the Professional edition of Metashape. Can you please check, which system is selected in the Reference pane settings dialog and which coordinates are displayed in the Source values tab of the Reference pane?
Best regards,
Alexey Pasumansky,
Agisoft LLC

ahuczekdesign

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Re: Odd stair stepping effect from export
« Reply #4 on: September 18, 2020, 01:52:10 AM »
Is the attached what you are looking for?

Alexey Pasumansky

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Re: Odd stair stepping effect from export
« Reply #5 on: September 18, 2020, 05:03:45 PM »
Hello ahuczekdesign,

Yes, that is it.

It appears that all the coordinates are identical and the referencing is affected.

Please perform the following steps to fix the problem:
- uncheck all cameras in the Reference pane,
- in the Reference pane settings dialog switch the coordinate system from WGS84 to Local Coordinates (m),
- in the Workspace pane right-click on the chunk's label and choose Reset Transform option from the context menu.
Then re-export mesh model.
Best regards,
Alexey Pasumansky,
Agisoft LLC

ahuczekdesign

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Re: Odd stair stepping effect from export
« Reply #6 on: September 18, 2020, 05:54:16 PM »
Thanks! I'm going to try that now. One question: Should I perform those steps (uncheck cameras, reset coordinates, etc) for each chunk, only all chunks, or the merged chunk? Or does it make any difference?

Alexey Pasumansky

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Re: Odd stair stepping effect from export
« Reply #7 on: September 19, 2020, 12:45:50 AM »
Hello ahuczekdesign,

You should do that for the the chunk which is used for the data export.

If you notice similar coordinate issues in the new projects, you can do that prior to the data processing.
Best regards,
Alexey Pasumansky,
Agisoft LLC