I noticed these patterns in the condensation on the inner surface of my car's windshield when I turned on the defroster. Usually when I see lines like these on condensation I assume it's because of snails/slugs altering the surface chemistry of the glass, but in this case 1) the lines seem too straight to be from a snail, 2) the angles are too sharp/consistent, and 3) there aren't any snails in my car. They also don't seem to be ordered enough to be artefacts from the manufacturing process (it's a new car). Anyone have any ideas?
Condensation patterns like this are commonly caused by tiny amounts of dirt or chemical residues on the glass surface that locally alter the condensation kinetics. I do not know what caused this particular pattern but try cleaning the window off with Windex/ammonia cleaner and a clean paper towel and see if the pattern persists.
By the way, people who work in cleanrooms with silicon wafers used to exhale on a wafer to see if it was properly cleaned. If it wasn't, swirly patterns of condensation would show up indicating contamination from the previous processing step.