can someone please eloborate on the techniques used to implement the quake/quake2 etc engines. I know wolfenstein and doom used ray tracing for the walls, floors and ceiling and 2d sprites for eveything else. I have already implemented a basic wolfenstein type engine but i would really like to know how quake2 with its 3d objects, slopping floors/walls etc was implemented. Any help appreciated.

actuarly it's not raytracing it's raycasting, they are slightly simmilar but then again not.
Basicly what it does is that it casts a ray for every pixel in the x axis, it then tests if it hits a sector wall, finaly it rendes the texture there with some kind of scale trick to it based on the distance to the sector wall.
So it's sort of like an 1D raytracer with a neat texture hack.

Quake, Quake 2 and so on use a totaly different method, it uses polygons instead of sectors and that texture hack.

Infact, every other 3D game use the same basic principle.

wolfenstein 3d and doom would have been better off if it would have used polygons, but at that period in time speed was a real issue.

Raytracing is slowly starting to return to the world of gaming(not that it was ever used in all it's full glory) and with the addition of raytracing hardware we might start to see applications that use some kind of raytracing augmentation instead of the regular effects/methods to enhance lighting and reflections.