GPL Track Creating - Traces
Authored by the GPLEA
Traces are a bunch of lines, parallel to the centre-line of each section that define the positions where the altitudes are defined. You can have between 2 and 16 traces on a track. Parallel may sound a strange word to use, but because the track is essentially a 2 dimensional construction (longitude and latitude), you can pretend that corner sections are straight - then everything makes sense!
A typical track will have traces defined where the interesting elevations are - the edges of the track, where kerbs are, where spectator banking exists etc. When designing your track, you should make sure that the traces are well-used - a pair of traces for the extremities of the track are normal; a pair of traces for one piece of banking for one short trk section is not acceptable.
Never use a trace near the track centre (latitude = 0). Ttrk23dow will not like you, you run the risk of getting all sorts of weirdness (mostly to do with the racing groove), and it's really not necessary to have one there.
It is much better to have one trace for the edge of the track, one for where the kerbs are, a couple for slopes and an extremity trace. That's 5 per side, or 10 total, which is a good number.
If you don't bother with the unk4 flags, you will find that as you add more traces, your <trackname>.3DO file will get much larger, and the FPS will decrease due to the number of polygons created by all those traces.
Here are two examples from the Nurburgring:
Right hand trace shown above is the same as the middle trace below - good re-use of traces by Papyrus!
See how noticeable the location of the traces above is. Now look at the TRK below (showing the second screenshot) and spot which traces are which:
Here is a pic showing exactly where all the 16 traces for the Nurburgring are located. See how there are a few used for the extremities, far from the driving line, and more where most of the action takes place (the run-off !). One trace is used near the middle of the track for the Karussell etc.
Transfered to the wiki: 15.04.2009