On the ipad? Impossible.
It's tricky enough trying to do it on a pc. You need a shed load of skill, not just an app that needs 2 or 3 button presses. I appreciate the word 'realistic' can be most subjective, but heck, even so.
I dont even know of an app that does crappy ones come to think of it. Walkthroughs and flybys require rendered frames, either pre or real time. This is not what ipad can (yet) do.
Ipad can certainly display pre-made animation and real time visuals, but even then, you need to have the source material to display in the first place.