selecting and measuring

[fbungartz]

Hello,
I am new to Agisoft Metashape and am taking macrophotos of minute structures. The camera that I use records GPS metadata, but since I am doing macrophotography the accuracy is not sufficient for the ruler to be calibrated correctly using these coordinate data.

I read the "PS_1.1_Tutorial (IL) - Volume measurements.pdf" and figured out how the create a scalebar and change its calibration. Good.

But I would like to measure a particular, well-defined area and the tutorial suggests to use the selection tools to remove secondary faces. Unfortunately these tools seem to be far to crude to fine-tune a selection. I tried using the masking tools instead, which allows for much finer selections, but it apparently only works on the underlying images of the model? I am not sure if a mask then can be converted to a selection?

Is that possible? If so, how?

Obviously the whole model is a composite from all the images and thus creating a mask on one image would not necessarily cover all the area that I want to measure... !?
Is there any way to use the much finer masking tools to create a selection on the whole model?

Also - it seems that masks can be loaded from an external application? Could I somehow export a projection of the model, create a selection in Photoshop and then load that mask into Metashape? Creating selections in Photoshop is relatively straightforward and extremely powerful, even being able to select very fine detail. If creating such a selection and importing it was possible I could fine-tune the selection much more accurately.

Not sure...

Thanks much for your help,
Frank

[Alexey Pasumansky]

Hello Frank,

Can you provide a few screenshots demonstrating the types of the objects that you are reconstructing?

As for the masks, you can load them to Metashape from black&white images using File Menu -> Import Masks command.

[fbungartz]

Hi Alexey,
thanks for your getting and sorry I didn't check for a response earlier.
Attached a screenshot of what I want to be able to measure. As you can see, it is a fairly complex structure and not really possible to select/mask this easily with the selection tools.
You are saying I can import a black & white image as a mask? How do I do that? The 3D model obviously is a composite of  many images. Am I supposed to take a screenshot, open it in some image editor like photoshop, select what I want to measure, invert the selection, delete what I do not want to mask, save as B&W and then somehow import back into Metashape?
I have tried playing with this, but haven't managed to figure out a way...
Thanks,
Frank

[Paulo]

Hi fbungartz,

I would mask the lichen structure you want to measure in a pair of photos and then Use Strict Volumetric masks option in generating Mesh. Then you will get a model of only the lichen structure and can use Measure Area and Volume.

As seen in attached screen, I masked a statue in 2 images of inside of a church. And Using Strict Volumetric masks in Build Mesh, I get a model restricted to said statue...

I hope this can help in your quest,

[fbungartz]

Dear Paul,
thanks much for the suggestion, but  unfortunately I don't think that will work.

I am not trying to construct and then measure the size of an isolated object like your statue. Unlike your statue the lichen covers virtually every photo of the area I have stitched together in metashape. Thus, unlike your statue it is not just one single object viewed at different angles, but it extends across most the 26 aligned images used to construct the 3D model of the relative flat surface. It is not just one isolated object viewed from different angles.
Perhaps a good analogy would be the facade of a building decorated by a relief of figurines. If you want to isolate all those figurines from their background, the flat surface of the wall, how would you mask those? You'd want not just to measure one single statue in front of the wall, but the whole structure spread across the wall...
 
Any advice is much appreciated.
Thanks,
Frank