Looks like an interesting project you've got there :-)
Tharg wrote:
However I need to make a custom surfaceExtractor but I don't know where to start. E.g. can I just start by copying and renaming a few files such as MarchingCubesSurfaceExtractor.h somewhere and then changing certain values in them to my names?
Yes, this is fine, but whether it is the bet approach depends on your goals and whether you need the original surface extractor. If you only need minor changes and don't need the original, you could just fork the repository and apply your tweaks directly. Or if your vision is completely different then you might want to start from scratch. But yes, in general the approach you describe is fine if you don't mind copying and renaming all the files.