Comment Re:What? Wait ... (Score 5, Informative) 125
The bit you're apparently not grasping is something called a spatial light modulator.
You've probably encountered one as a digital cinema projector, or possibly even own one for PowerPoint presentations.
Couple it with a microwave radar or ultrasound sonar, and you can track individual raindrops and then cast shadows on them.
Sounds unnecessarily expensive for consumer automotive, but might be nice for buses/locomotives, emergency vehicles or passenger aircraft.