I’m not sure what you mean by “3D sprites”? If you’re referring to something like particle systems, or perhaps pseudo-3D like Space Harrier (SEGA GENESIS), yeah definitely. If you’re thinking textured polygons, then you can fake it… kinda… very slowly.

Flash is a 100% 2D engine. It uses no hardware acceleration (though it has very fast 2D operations written in native assembly). If you want to do 3D (polygons, textures, etc.), it has to be done like it would have been done in the pre-hardware-3D days, which means a very limited number of polygons and an even more limited amount of texturing on those polygons.

There’s still a lot of tricks, though. Flash can do scaling very fast, so you can do a lot of pseudo-3D effects with very simple math (scaling based on distance), including full particle systems. Combined with Flash’s bitmap filters (blurs, drop shadows, glows) you can do some very nice effects.

As far as 2D physics goes… I’d recommend checking out the guys who did ‘N’. Their homepage has a link to the a presentation they gave on doing high quality physics in Flash (it’s what they used in ‘N’). The good news is that it should be even faster in the Flash 8 and Flash 9 players as ActionScript has been significantly optimized (I believe they were targetting Flash 7).

So, yeah, 2D physics isn’t too much of a problem, as long as you’re reasonable.

Is it reasonable to try and implement 2D physics with 3D sprites in Flash?