Rain Effect Part 1

In creating the rain effect I used a scene I already had lying around that already had a water material within it.
First off I set up the lighting for the scene using an IBL, I usually use IBL's as standard in scenes anyway, however, given the reflective/refractive nature of water It was important to have something in the scene that can provide reflections/refractions from every direction.

The scene I was using as a base just has a standard piece of "island" geometry surrounded by water.

The material being used for the water. The most important part is the Fresnel reflections/refractions and the IOR. As the IOR of water is 1.33, it is important that this matched to create as physically accurate a material as possible.

This is what the water material looks like when applied to droplets of water that I modelled.

A basic rain-type effect being emitted from the surface above, there is a gravity force acting on it aswell so that it falls realistically.

I experimented with instancing physical geometry to get the right look for the raindrops, however this proved impractical as the poly-count always made the simulation run very slow. The geometry I was using at this point did not look like rain either.

 Using just points I was able to create a much better effect, aswell as making use of the "strand" system in ICE to create particle tails that mimic streaks of rain.

This is the node setup for the effect, the effect also has a "wind" force acting on it to create a bit of turbulence and to produce a more realistic effect.

This image just shows me experimenting with how to light the effect, in the end I tweaked the IBL to look more like a stormy overcast day, I also had a front light to mimic a weak sun shining through the clouds.

This is a very simple composite of a few things in Photoshop. The Raw render, a blurred version of that render and a blue-ish colour grade. I could achieve similar results in 3D with Motion blur and a grade added within the compositing software.

However before I do that I want to add the "misty" effect that you often see with heavy rain storms, I also want to change the wind so that it blow the rain more violently.