I worked on this earlier this year. I was going to keep doing it, but I eventually scrapped the project as it got too hard & I had other stuff to do. Someone might be able to use this code & keep working on it though. The next step would be collision detection and rotation (and proper polygon filling order). It needs to be more efficient as well, but that may be beyond my abilities.
I think it didn’t turn out that bad anyway. Its based on the 3D tutorials here at kirupa and the platform based game tutorials by TONYPA at http://www.tonypa.pri.ee
Anyway, I hope someone can use this to make a proper 3D engine with actionscript.
PS
Its not a proper 3D engine at the moment, I guess its more fitting to call it psuedo 3D. It only has forwards/back side-side movement, no up & down - but that wouldn’t be too hard to add.