Moving precipitations when camera's moving

Hi,

I want to know how to move precipitations when camera's moving, like in CaelumLab (when you move camera when it's raining for example, you can see the rain moving to you instead of just falling straight).

EDIT : I found it, but the rain is moving too fast ! How to slow it down ?

Thanks by advance

Currently the only way to do that is to set manual camera speed and divide it by a constant of your choosing. Camera speed for precipitation is not measures in any meaningful unit (like m/s or such). Just tweak it until it works for you.