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How would one render a scene to look like it's raining...(without using photoshop)?

I can think of a couple of methods off the top of my head.

First, if your software supports it, you could use a particle system. You may need to convert the particle system to polys, and manually animate for motion blur. I've used this in the past, and although gives the most realistic result, it also increases your rendering time considerably. Best for close-up shots where you don't need to see a huge amount of rain.

Another option, which I haven't tried yet, would be to use a series of planes with a rain 'streak' texture applied. You would need to use the ghost layer transparency effect (two bsdf layers with a blend map). It may require much more tweaking to make it look right, but theoretically would render faster.

I'll try to do some experiments on this method tomorrow to see if it's a viable option.

Well, I tried two different methods for creating rain using multiple planes. One method utilizes a dot type bump map that requires Motion Blur to be activated. The other uses a streaked bump map that does not need Motion Blur. (all test images were rendered to SL9)

These are the two maps I used. I'll upload the MXM in a bit.



Here's a screenshot of me scene setup. It's pretty much self explanitory.




These first two shots show the dot based material with motion blur. I changed the amount of roughness to make the streaks appear more or less.




These following shots used the streaked bump/weight map with no motion blur applied. You will note that with the one set to roughness 50, the streaks are much brighter and cleaner that the 50 roughness dot version.
However, when I lowered the roughness to 10 (in order to dampen down the brightness of the streaks), you can see that those drops below the camera are only showing highlights at the very top of the 'tube."




Since I used a setting that put the sun near the horizon, we were able to get some decent, faked blur streaking using the second method. However, the method would definaly not work well if the sun were higher in the sky.

The dot blurred method gives the most realistic results - even though it is slower clearing up. However, the streaked map method could be used, depending on your lighting and camera position.

Here's another quick-and-dirty test. Scene was only rendered to SL 6, using a cityscape model by Stonemason (stefen morel). I'm re-rendering it now for longer just to see how it comes out with a higher SL.


Raw rendering



With post work in PS CS2


I used the dot/motion blurred method here. Rather than populate the entire scene with rain planes, I grouped smaller groups of planes around each light source (facing towards the camera) In addition, I placed another directly in front of the camera, with an independent light source behind the camera that would illuminate these 'drops.' I used Multilight to adjust the intensity of the rain streaks in the foreground. There's also some lighting from a night-time HDRI sky, but I dampened that down quite a bit with the ML.

What also helps out to create the illusion of rain is to make the ground "wet." In this case, I just took the existing ground textures, and added a second BSDF layer, set the ND to 1.33, roughness to 10, Transmittance to near white, and gave it a weight setting of 50, leaving the original layer as-is (basically the same way you would make a glossy plastic material). You could take this even further by putting a ripple bump map on this glossy layer.



Hope this gives you some ideas on how do do rain. As I mentioned before, if you want to do close-up shots with rain, I'd suggest using actual geometry (tiny spheres with motion blur). That will give you a more realistic image. However, for large shots like this, the planar cheat seems to work ok.

Good luck!

That confirms it! I declare Micheal Logue as the King of Maxwell Atmospheric effects!!!

Because that's f--king sick!

Luis

LOL!

Thanks Luis!

Fabulous technique! ...predicting a move to the Tutorials section in 5...4...3...

feck me mate

tutorial material michael! the effect is amazing.