About engines. I am not sure about RTCW, and I think you are right that no modifications to the engine was made. Raven hacked it up pretty good for SoF2 and other products, and there are some very handy improvements for outdoor levels. I am quite sure that CoD also uses an extensively modified engine.
The real change, however, is that the map compiler is being constantly improved (Now at 2.5.12 or so, new one about every two months) So you can make a lot of really pretty things in Q3 now that you could not do in the first place.
I think that it is not so much about what engine is 'better', but what it is good at. UT draws all polygons visible, and takes a lot of time to find out which polys that are so. Quake-based technology, however, splits the map into a lot of areas, and precalculate from each area what other areas can be seen. If you stand in an area, Q3 draws all polys in all areas that you can see part of from your entire area. It means it draws a lot of unescessary (sp?) polys, but is real fast about finding out what to draw.
This difference has important aspects for level designing. Quake requires that you break lines of visibility between major areas of you map, because if you can see a small part of it, all will be drawn. This is what makes it almost impossible to make a map like Ruins or Stalingrad, as almost all areas can be partly seen from all other areas. The same goes for any forest style map. The alternative is to use fog. It is then possible to cut off all polys at a certain distance, but the original Q3 engine is horrible slow at making fog (This is an area where the SoF2 engine mod really shines).
It also make it difficult to make smooth-running terrain, as most types of terrain does not have the all-important visblockers that you need to cut down on excess polys. It can be done, but requires a lot of time and skill on the mappers part.
However, If you make fairly enclosed spaces, you can make sure that almost all drawn polygons are drawn where you can see them. And each polygon is drawn much faster, because the engine does not have to spend a lot of time figuring out if the poly should be drawn or not. Thus Q3 handles better for maps with welldefined areas with only little contact between each other, and most passages will not be straight in order to block of visibility. In realism terms, this convert to urban areas with inaccessible rooftops, rather than open country. A competent mapper could do a far more detailed version of A City Block for Q3, but not a Ruins.
DS-Trainingground could be done even on both engines, as their structure dictates that you are able to see most of the map from most of the map. However, if a map like DS-Trainingground was ported poly for poly to TC, most players would think it looked to "blocky", as some of the polys used are quite big. An equivalent Q3 map would have raised the cliffs, so that you would have narrow passages up to the plateau. You would still have as many access points, but they would be more enclosed. Further, the half-raised cliff between the spawns would be fully raised, and a bit broader. Thus, you would be able to make some vis-blocking of the map, and be able to raise the number of polys in each area (I have given this some thought with a conversion in mind, but I have no time to start another mapping project right now). I am not saying that open land cannot be done, just that there is a price to pay for it.
-Freshmeat (Ok, I write to much and work to little)
