Building Up The Effect

After a failed attempt to get the scene rendering in vRay (its being funny about rendering nParticles), I rebuilt the scene from scratch in Maya 2014 (it was in 2015 previously). I also went out and shot an IBL to illuminate the scene and provide the rain something to refract.
I managed to create the "streaking" effect by using instanced geometry over the particle system, I had previously tried to create the effect using motion blue, but the result was not as good and it increased the render times too much.
Currently the scene is also using Maya's simple fog environment shader to provide a bit of atmospheric perspective.
I have here a play-blast of the effect as it is currently, as well as the IBL I used.

Fog and Lighting

The way the rain is lit is going to be very important. Rain is hard to pick out a lot of the time because of its transparent nature, especially when situated against a grey sky. Although the size of the rain plays an important factor - its far easier to see bigger drops - the way its lit is still the most important factor in creating a good effect.

I've also been out gathering a bit of reference pertaining to the environment fog. Now, its been quite bright here today and so the fog is a lot lighter here than it will probably end up being in the scene itself. It still serves as good reference for me however.

I am also currently reworking the scene in order to render with V-Ray, this will hopefully lead to a further improvement in render times.

A More Efficient Way

Spending a bit of time within the options in Maya, I found a more efficient way to create the rain effect. That is through the use of Motion blur.
Using an nParticle system to generate the droplets, and using a Sphere as the particle geometry with an Mia material applied (With settings in place to match that of water).
The streak like effect comes from the Motion blur which is applied to the render.

More Bifrost

Trying a more complex Bifrost simulation, mainly to see what my system can handle aswell as how to do some basic things like collisions with geometry. It is an impressive tool, and I want to see if it can be used to create rain, or if it can be used to enhance the rain effect in anyway. I'm thinking that it may be a good solution for creating the more "fog-like" aspects of a storm.

Rain VFX

I've found a lot of references to After Effects being used to create rain in post for certain shorter films. A lot of the references I've found for larger budget films involve the use of a special effect, rather than a visual effect. Such as in the Noah post I made earlier.

I did however find a very interesting video a while back (I forgot to post it) on how they created some of the water effects in "Battleship". Its a very interesting video, and I feel that a lot of this could be applied to some rain effects. I have also been spending a bit of time in the new Bifrost system within Maya 2015, figuring out a little bit about the system. Within a few minutes I managed to put together this very basic simulation.
Taking this further, I would like to try and work something like this into my rain scene.

Rain Issues

This effect is proving somewhat impractical to render. Mainly due to the heavy use of Refractions in the materials. I think that with some tweaks to the lighting, the actual effect will look allright though.
I have attempted to render it in realtime using a CGFX shader, but this did not work either.

I am going to try reducing the fog effect to see if that is an acceptable solution.
Oh, and I do want to try some water effects within Maya 2015's new Bifrost system.

https://www.fxguide.com/featured/bifrost-exclusive-first-in-depth-look/

More research

So, while looking up some VFX videos I came across this one. Its got some advice in it that i shall be working into my setup. Such as back lighting the rain more. I will either crank up the sun or add in another light for such purposes.