[Algorithms] Ellipsoid Engine used in game "Ecstatica": how its done?

[Andre K. <po...@an...>]

hello,

i recently re-discovered the game ecstatica from andrew spencer productions:

http://www.gamespot.com/pc/action/ecstatica2/images.html

my question is - how did he draw those ellipsoids that fast ? (ecstatica 
1 was from 1994 and was quite impressive as compared with those low-poly 
non-textured models in for example alone in the dark)

i can somehow imagine how to render fast, axis-aligned ellipsoids 
including some z-buffer,
but i cant imagine how those ellipsoids could be rendered with a free 
long axis. wouldn't this require a full matrix multiplication per pixel? 
even with lookup tables for sin/cos i can imagine it would have been too 
slow on 1994 hardware.

another question: how is collision detection done int alone-in-the-dark 
style games with pre-rendered 3d-backgrounds?  ok, visibilty check is 
easy - just store a z-buffer. but how is collision with the pre-rendered 
background done? did they store some kind 3d-z-buffer ? maybe with 
voxels twice or 4 times the size of the pixel resolution? or did they 
just define a bunch of bounding boxes?

third question/idea: would it be cool to make some pixelshader on modern 
graphics card, implementing those ellipsoids and making a modern variant 
of ecstatica? this would give some nice organic look. and with todays 
hardware, one could maybe literally spit out millions of those ellipsoids..