(2020-01-22, 23:31)Gerald Lasser Wrote: How is e.g. LDView (or LDPE) deciding what to put on top of a stud? Are they only looking for a "stud.dat"?
When primitive substitution is enabled, LDView looks for "stud.dat" (or "stu2.dat" when running in low-res mode), and uses a disc with a LEGO texture on it in that case instead of an unadorned disc. (It also keeps track of mirroring to ensure that the logo itself is never mirrored.) There could be other primitives that deserve a LEGO logo, but LDView doesn't support doing so with them. If you have a Scala part, and that contains a stud that is identical to a LEGO stud in every way except for the logo on top, I personally think it would still be best not to use stud.dat on that part.