masking the sky using background photos

[3DWinter]

Hello, Agisoft support,
I am trying to model a cliff from a collection of pictures that have some sky in the background.  I cannot figure out how to mask the sky when mosaicking a cliff.  Chapter 6 in the manual, specifies instructions. Particular how to import the masks. But is the step to import masks is also when creating them!? Step 3 in the manual,  "3. When generating masks from separate or background images, the folder selection dialog will appear.  Browse to the folder containing corresponding images and select it."

I have a few questions about step 3:
1. From the manual step 3 in the quotes, what is the difference between separate and background images? Isn't the background image, a separate image that only has sky or using one of the images with a sky as a reference to classify all other images?
The next sets of questions are regarding the Import Masks, see attached (import_mask_tool.png):
2.  In Method:  From Background,  is that from a not yet imported picture that only has a background, if yes, then one file should be applied to all images, no!?
3. Most confusing is the Filename template, I understand what it is,  if I  am importing matching mask for each image, but I am in the process of creating masks for all the cameras.

Maybe my confusion is I am trying to use the Import Mask to generate masks from a background, either picture that only has a background, or pictures that have some background and already imported.

I am so confused.

[Alexey Pasumansky]

Hello 3DWinter,

I think that the "background masking" approach wouldn't be applicable to your project. As under "background" image we mean the image taken from exactly same camera location with the same camera orientation, but that captures only background without the object of interest. So in your case it should be a picture of the same sky (it should be still) without the cliff.
Usually background masking is applied for the studio captures with the multi-camera rigs that allow to take a synchronized shot set with the object of interest and without it.


I think that using "tie point masking" may be more appropriate in your case:
http://www.agisoft.com/index.php?id=49
even though you will need to create some masks, you do not have to do that for every image.

In case the sky is more or less of the same color, you can use the masking-by-color script:
https://github.com/agisoft-llc/photoscan-scripts/blob/master/src/masking_by_color_dialog.py