hi
now the long answer, I hope its not too long, and I hope there are no typos:
the core sentence is "the prefix has to be the very same everywhere". its called prefix in CMagic-4 and GPxPatch. in gp4builder the same thing is labeled "Wad Name".
I explain along an example, where I take original "monza2001", rename it to "monza" and load it in slot 16 where normally indy sits.
1) I start with the .dat. in my installation in the circuits-directory, I make a copy of the original-monza-file s1ct15.dat, rename it to monza.dat, and open the latter in the gp4builder.
there in the physics-tab, in track sectors I select the "initial sector", and in the track properties window I hit the "Show GP4 Infos Data". here I insert my prefix "monza" in the field "Wad Name", close the window and save the .dat.
2) I start GPxPatch, make sure "GPxTrack" is checked in the first tab, and select the "GPxTrack"-tab, hit the edit-button and edit the line in field 16 to circuits/monza.dat (or load it via file open dialog), start GPx, select "indianapolis / united states", and hit "drive" ... and watch gp4.exe crashing at "the middle of the bar". the .wad is missing.
3) so I make a copy of monza2001.wad and rename it to monza.wad and again start GPxPatch and gp4, select the track and try to drive it. this time gp4 loads a little bit longer, and crashes again. the proper maps-name in the .wad is missing.
4) I open monza.wad with easywad, open "maps" and there I rename "monza2001" to "monza", and again try to load a session in gp4. it again loads longer than before, the bar almost is at the end when it crashes. the .gp4- and .col-files in the .wad are missing.
5) I again open monza.wad with easywad, open "maps" and "monza" and there, in the "meshes"-section I rename "monza2001.gp4" to "monza.gp4", and in the "other files"-section I rename "monza2001.col" to "monza.col". then I give it another try loading a session in gp4. its still crashing, now at the very end of the bar. the .anm file is missing.
6) I open anim.wad with easywad, open "animationdata", drag "monza2001.anm" to the desktop, rename it to "monza.anm" and drop the latter back into anim.wad, and give it another try, and yep, monza loads !
but soon I notice, something is missing: the tarmac, on the track and in the pit lane.
7) I again open monza.wad with easywad, open "maps" and "monza" and there, in the "other files"-section I also rename "monza2001_track.bin" to "monza_track.bin", "monza2001_pitlane.bin" to "monza_pitlane.bin" and "monza2001_pitverge.bin" to "monza_pitverge.bin". now its OK.
there are some more files you could rename in the .wad in the same way in "other files" and in .\maps\ressources but whether they make a difference or not I dont know too well. at least its not a big difference. most of all, the track loads and works without it also.
but do NOT rename the texture files ! else you get white areas in the game where those textures normally would show up. if you want to rename the textures you also have to do so with gp4builder in the .gp4-file.
and at last, whats missing yet is a few things in the gp4-menus, the trackname in the track selection window, the trackmap and the loading-image. but they are unfortunately not covered by GPxPatch.
as a summary, here a list of the steps above, with TRACKNAME as prefix
1) rename .dat (optionally) and include the new prefix in the "GP4 Infos Data"
2) insert the .dat in the wanted slot in GPxPatch / GPxTrack
3) rename TRACKNAME.wad
4) rename .wad\maps\TRACKNAME
5) rename .wad\maps\TRACKNAME\TRACKNAME.gp4 and .wad\maps\TRACKNAME\TRACKNAME.col
6) make anim.wad\animationdata\TRACKNAME.anm
7) rename .wad\maps\TRACKNAME\TRACKNAME_track.bin
rename .wad\maps\TRACKNAME\TRACKNAME_pitlane.bin
rename .wad\maps\TRACKNAME\TRACKNAME_pitverge.bin
and be aware, as soon as there is a prefix in the .dat, and you use GPxTrack, the prefix IS used and the correspondig filenames are needed. but you can disable GPxTrack anytime again of course.
regards, addie