D&D 5E Determining Visibility [RAW]

[GMMichael]

By asking specifically for a RAW interpretation, the OP was certainly not looking for common sense. . .It would be more interesting to see specific examples and how different DMs would rule (if it even mattered) about whether or not a character can see another or not.

And unfortunately, @LordEntrails didn't give us a specific example. That would also be interesting to see.

My favorite source doesn't mention grid squares, which fits well with D&D 5's (non) branding as D&D Lite:

Cover :: 5e.d20srd.org

 

[LordEntrails]

I didn't have a specific case. I was wondering because there was some discussion of the modified LOS behavior on FGU. Folks were arguing what was RAW. Since I couldn't find it, I knew folks here would know exactly what page/section it would be in the rulebook(s).

Appreciate everyone who jumped in with RAW answers. And even with other comments.