ROM Hack Question ACNH - Way to modify collision files (PCB)?


New Member
Aug 8, 2021
United States
Hi all - sorry if this isn't the right place to ask, I can't find any info on this anywhere!

I've been working on model mods for Animal Crossing, I've figured out import/export of the main models, but the collision files are kind of a black box it seems. At least I'm almost certain the PCB files stored with the model files are collision files; there's no clear information stored in them that you can read in Switch Toolbox, just hex values, but I haven't found any other files that could be collision instead (such as KCL, which is used by other switch games).

I was hoping to get some vertex coordinate data from the extracted PCB file in a hex editor, but as far as I can tell, they're either stored in a way I can't read or they're stored somewhere else. One model I tested was the FldUnit model (a square of grass on the island), which has only 2 tris / 4 verts. The corresponding PCB file has very few hex values, seemingly proportional to the simplicity of the model (compared to other PCB files I've checked), but none of them outright matched the coordinates of the base model (all y0, x and z all -5 or 5). If I could find vertex coordinates, it would be simple enough to turn that information into an OBJ file and make changes in Maya, but I can't make sense of it.

As far as I've seen, there haven't really been mods for ACNH that have collision edits, so my guess is no one has figured it out, or at least hasn't posted info anywhere I can find. If you have any idea about the collision in the game, or resources to check out, it would be very helpful! It's not that big of a deal all things considered, as most of my model edit plans will work with existing collision, but if I could change the collision it would really open up some great possibilities. Animal Crossing is a blast to work with!

In any case, thanks for reading!
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