So I spent the past months going down a rabbit hole. When the game loads a track it doesn’t just inflate all the parts and dump them into RAM, as it does, it modifies some of them, and even calculates some things and inserts them between the parts.
“Well”, I thought, “if the game does it, then I must too!” And that’s how I spent the past few months decompiling the track loading functions by hand. Only to realise, as I got deeper and deeper, that to do the job properly I would more or less have to write an N64 cpu emulator to emulate the whole game.

At that point I gave up. That point was yesterday.
When I thought about it, the data I want to replace is what’s in the ROM, not the RAM, so really I don’t care what the game does with the data once it’s in the RAM, so long as the data I put into the ROM is compatible.

Moving on then, I’ve now parsed the basics of the track models, bringing me back to where I was last time I tried this years ago. Onwards!

One of the Hawaii track variations