He can't really do that with the present approach. :)

Each 'drop' of rain is really a circle painted using the reflection scaled to the size of the drop. This approach is very fast, but won't scale well with odd-shaped drops and larger drops. With a small enough spherical drop, it's a good enough approximation for refraction.

With larger drops, you'd start to notice that the reflection isn't a refraction (i.e. the reflection is cutout in the shape of a circle, rather than truly refracted as in a drop of water).

Other approaches could be adding more expensive texture transforms, or WebGL + a refraction shader for bigger and/or non-spherical drops.

Obviously at this point we should begin ray-tracing.

I'll call John Carmack.

I would add that its not realistic as raindrops combine because of surface tension when they touch each other :(

One thing I noticed in the second demo is that the rain drops move too perfectly in the diagonal. I'm assuming the effect is to represent wind, which doesn't typically blow at a constant angle and speed.

Overall a wonderful demo.

Not if you wax/RainX the surface :)

Come on dude lets not get picky this is beautiful.

It's feedback, why else would he post on HN - great start.

Sometimes you show people things to show people things.