Well, the topic title says it all  

I've got that document ad I've read it already, but it doesn't really tell me how to place the rain effect in-game, it only tells me how it works and it's command lines.
I've saw an explanation on this forum that says that I've got to place an brush with the "outside" texture on the area that I want it to rain and an "worldeffect_command" to make the actual rain, but my doubt is what "key" and consequent "value" do I have to put?
I've tried using the commands on the document, but I don't know which goes for the key part and which goes for value.
Thanks  

O.K. this is how I got my rain working in a sample level that i was just learning on.

1. In my skybox I placed an "OUTSIDE" brush the size of the area that I wanted it to rain in.

2. Place a worldeffect_command inside of  the outside brush.

3. I made a trigger_multiple (only once) and targeted it at a script_runner (key: script value: rainscript). That way when the player hits the trigger in the level, the script will run.

4. BSP your level.

5 open BeHaved and write the following script:

set ( /*@SET_TYPES*/ "SET_CONSOLE_COMMAND", "r_we rain init 500" );
set ( /*@SET_TYPES*/ "SET_CONSOLE_COMMAND", "r_we rain height 0.5" );

6. Save your script as rainscript and compile.

7. I compile mine by dragging the rainscript.txt on top of the IBIze.exe in windows. That way the IBI file is in the same directory.

8. Make a folder in your C:\Programfiles\SOF II Double Helix\base\scripts directory with the name of your level for the name of the folder.

9. Place your rainscript.ibi file in the folder you made above.

10. Presto! when you run your level and walk over to where the trigger should be in the map and touch it it should start to rain inside of your OUTSIDE brush.

Hope that helps!!
 

It helps, thanks.
Sounds a bit complicated  

Yeah, but you just can't use scripts for everything, otherwise you'll just get an unholy mess on your mod

O.K. I figured it out... it seems so obvious now... DOH!

All you have to do is make an outside brush, put a worldeffect_command inside of it. The key and values work like this:

Key: "c0" (without quotes)
Value: "rain init 500" (without quotes)

Key: "c1" (without quotes)
Value: "rain height 0.5" (without quotes)

...and so on

Is that easy?
Thanks

Your welcome!