Rain effect

[zammbi]

Just wondering what everyone else has done for their rain effect? I don't want to reinvent the wheel when I don't have too.
Or any suggestions on creating ok looking rain which is quick enough for the software renderer?

[paulscode]

The cheapest way is as a 2D overlay using a texture with alpha.  If you are using Photoshop, use a process similar to the one described in this video to create the texture.  Of course, you would ignore the animation and scene set-up stuff in the video (you are just after the tileable rain mask).  You want to use the mask to generate a texture with degrees of alpha, rather than applying it to a photo (similar to the way I made the glow and smoke textures, which I've described in other threads here -- I can give you a step-by-step if you are not super familiar with the Photoshop menus).  Once you have the tileable texture, the cheapest way to animate it is to incrementally change the u/v coordinates to make the rain fall downward.  Another option is to animate it with a texture effect (slower in my experience).

If this isn't realistic enough for your project, I am working on a method that incorporates the rain as either particles or planes into the 3D scene, but I haven't yet found a way that is both cheap and looks believable.  I'll be sure to post an update if I can figure out a good method.