3D isn't amazingly hard, and you don't need lots of maths like the facebook discussion states you do. Im working on a
Map Editor simmiler to Valves Hammer and i suck at maths as well as algarithums. If you needed maths to render 3D objects then i wouldn't be able to do anything.
I also have tried making Game Engines, The main reason i stopped was because i could never find anyone to make models, etc. So i didn't see any point in continuing. The
Unity Engine is proberly the most developed engine i created, it could load Quake 3 BSP's (Meaning nearly every game based on the Q3 Engines's Maps would load). I mainly focused on Emulating Return To Castle Wolfenstine, i even got the scripts mainly working (For example on the first level of RTCW you got the same camera scene as in the real game... just without any NPC's around etc). Screenshot section of its website shows what it was like.