It looks much like it does in a car. The drops smear upwards and distort the image through the smear. Maybe I can get a pic today. It's raining here.
It has to rain pretty hard for the wipers to be needed. I only use them 2 or 3 times per year. Usually the air flow stretches the smears and dissipates them fast enough.
On a fighter - type canopy the smears stretch and dissipate rapidly.
Thanks - that's helpful already.
Frosted windows in a C172 like the "snowline based on metar temperature" would be fun, then once you start the engine, start defrosting first near the vents and then further until in like 5 mins the whole cockpit is cleaned Could do the same with fogged windows during humid weather.
The idea is to have basically all these effects modeled aircraft side.
For instance, the shader can't know under what angle the airflow will go over a window as a function of airspeed (and hence predict the splash angle for drops) - but a human can usually make a reasonable guess just by looking at the aircraft. So the modeler will have to provide the splash vector as function of airspeed. Likewise, the modeler will have to decide under what conditions frost appears, when glass would fog, what to do to remove fog and frost,... the shader will just accept flags which affect the visuals and do the light scattering physics of these (ice flowers and fog are strong Mie scatterers, they are way more pronounced if the sun falls through them, and that I can model easily).
I guess similar with a scratch/dirt model - the shader can draw the overlay texture, but the modeler has to decide when this happens.