I am aware that rFactor doesn't have rain, but I have a theory that might work and I'd like to ask the pros if they think it's worth pursuing. Although,,, it might be too late seeing as rF2 is just around the corner. Krunch's skybox follows you around the track and is not static, so we could add to the skybox and put a cylinder in the centre close to the car with a few layers of animated rain texture. This way where ever the camera is it will see the rain. I don't know how it would work on the winshield yet, I have to think about that one, cause cameras are in all different spots and cars are different shapes. Here is an example.