Alicornutopia

A combination of Effulgence and the various things on Alicornutopia (the RP hub, not the forum) have awoken my latent interest in sandbox roleplaying. I don't trust myself to work with characters from other people's canons, though, or even AU versions of them; there are very few characters other people have written who I'd feel confident in my ability to play in a non-OOC fashion, and while the AU tag helps a bit, I still don't trust myself with it at the moment, because of the slippery slope from "mildly OOC relative to canon but justified by the AU" to "pretty much an OC wearing a canon character's name and face". However, I still want to do some roleplaying at some point, so I've started working on developing a world which has been sitting on my hard drive for a few months.

I've currently got a bunch of loose details which I haven't quite put into a complete package yet, but I know the basic shape I want the package to take, and I get the impression that the RP format allows for a lot more impromptu filling of cracks in the world than I'd be able to pull off if I were trying to write a novel. So my basic question is: how much background knowledge of the world should I build up before I start actually dropping characters from it into sandboxes?

That depends! If you're doing structured sandboxing with a specific partner, then the question is how comfortable your partner is with the available level of detail; if you're just flinging characters into the void of e.g. panfandomsandbox and seeing what they hit, then the question is how much background you need in order to be able to play the character consistently, and that can vary from "not much" to "lots and lots" depending on your personal style and comfort levels.

I'd say a good ballpark for either might be, can you describe the character's background and cultural context to somebody in high-level overview and have the person understand what you're talking about? And when the person asks you questions, can you answer them on the spot, either from material you've already come up with or by inventing more details as you go along? If "yes" to both, you're good to go.

I'd like to point out that if you like Luminosity, it doesn't make that much sense to disapprove of OCs wearing canon characters' names and faces.

Kappa: Thanks for the advice! Yeah, I was planning to just drop into a void of that sort, once I was satisfied with my worldbuilding. Using your ballpark, I guess I've got a bit more to go; I could possibly pull off the high-level overview, but I doubt I'd be able to answer questions on the spot with my current knowledge of the world.

Alicorn: I don't have a fully categorical problem with it, but I've found it to be one of the rarest fanfic-things for people to get right, to the point where I find it safe to assume that I'd get it wrong if I went down that path, and typically assume the same of other people. Sometimes it's done well enough to not bother me, as in the case of Luminosity, but that doesn't prevent me from holding a strong distrust towards the pattern as a whole.