How to calculate such cross sections?

Question

infographics

There is a course project on the topic "3D modeling and visualization". The plans are to do the following:
build one of the figures (cube, cone, parallelepiped, pyramid, sphere), select arbitrary points on it and connect them. Calculate the cross-sectional area.
Question: in what environment it is better to make it? (I thought to use unity).
Are there any recommendations on how to do this?
The picture should look like the one shown.

Answer 1

You can build one at www.geogebra.org. This is not a software solution, of course, but suddenly it will come in handy as an auxiliary tool.