easy 3D graphics for rendering geometry?

[gsal]

What would be the easiest way to go about offering 3D graphics for the
purpose of rendering geometry?

Suppose engineers (my co-workes) have to design some enclosure,
nozzle, bracket, or whatever physical part/component, I would like to
write a program where they can at least see the resulting geometry and
navigate it, i.e., zoon-in/out, rotate, pan.  On the side, I could
have data entry fields with the input parameters and when something is
changed, the graphics can be updated "immediately" (after the
necessary calculations have been done).

I know I need to learn something, and I am willing, I just need help
choosing what to learn.

I don't have any experience on this matter, don't know OpenGL, Mesa,
VTK, VRS, Maya...and all seem to have a steep learning curve. I don't
know any of the "other" graphics packages more oriented for game/
scenery/movie development (Panda, etc.), either.

I do know my trig and build my FEA parts parametrically from points,
to line, to surfaces, to volumes or from volume boolean algebra.

I would like the choice to be some kind of module/API that works
equally well on Linux as in Windows.

So:
What would be the easiest way?
and would it be worth learning?
or
is it better to shoot for something not so easy but worth learning?

thanks in advance for any pointers.

gsal