This has been a thing for a while now, and I'm finally giving it a try. Since I'm fairly certain no one else here cares has done this kind of thing, I'll keep this fairly short. Basically, you need a certain plugin for either PJ64, or 1964, which allows you to rip models, and textures that are currently loaded into the N64's memory in that given frame. This "scene" then must be opened with a program like Blender, or Milkshape3D (both of which have the file format plugins for the .wrl format). You'll need to manipulate the model slightly, as for some reason, the N64 stores models with mirrored X/Y axis, and sometimes generates junk material/ texture files. From these programs, you can export the model as pretty much any 3D format you want (.obj, and .3ds are the most common). You can select, or delete stuff you don't want, and isolate a certain enemy, or character model, or rip entire stages.
I haven't ripped anything note worthy, or anything that hasn't been seen before, but I will likely post some of the more complex stuff I plan to rip, if I ever do. Even though the steps sound easy, you still have to play through the levels, and loading zones to get everything. This will take quite some time for a game Like Rayman 2, and especially for either of the N64 Zeldas. I'm pretty much obsessed with 3D models, and I plan on ripping the entire maps from the N64 Zeldas. A few of them have been ripped already, but to my knowledge, no one has ripped all the maps, and put them in one package.
There's really no reason to do this other than boredom, and curiosity. Plus, I guess someone around here has to get an asset package ready for that 3DZC, you know, whenever.