3d mapping software from monocular images


I know by sure that it is possible to build a 3d model of an open area just by taking some pictures of it; I know because I did it:

This is “Barbagallo crater” of Etna volcano, in Italy; I shot ~50 pictures from above, walking around the rim, and the I processed it by Autodesk Remake (now no more free, but ther are also 3d Zephyr and Regard3D still free).

I also know that it is possible to build 3d model of the interior of a room by just a dozen of 360° pictures (I read a paper about this), but I couldn’t find an off-the-shelf SW to do this: I should split by hand each 360 image into 6-10 flat images before making them processing by 3d SW…

The question is:
does it already exist a SW which automatically gets 360° images and turns them into a 3d model?

Second question:
Does it exist a SLAM (Simulteaneous Location And Mapping) SW which can work in realtime on a standalone underwater drone? The algorithm is quite processor-intensive, but it can also be tuned to give coarse results, so maybe somebody implemented it on a Raspberry or something like that?

What I’d like to do is create a 3d model of an underwater cave.

Thanks for your help.