the bit you've marked as "unknown" is the world position node scale. because if you just used the world position node raw your "faked" UVs will be the same size as the world - so they have that node to control the tiling. In this case the 'rain' bitmap will be 64 units wide in the world.
Open up the example night and day transition map in UDK. It has examples of this exact thing. You should just be able to use a world position node as UVs to make water run downwards.
I'm trying to created a material that can be applied to any object and have a panning rain normal wash down its surface. Basically, I'm trying to make it look like water is running over the object. A simple solution would be to simply have an additional UV map. However, in this case, I don't want to rely on that for two…
Aha! Thanks sprung, that's exactly the kind of thing that I was looking for! I've managed to isolate the chunk of the material tree that creates this effect: Panning Orientation Masks Normals Blending Unknown It seems that the approach here is to create three planar UVW 'projections' and then blend them all together. I've…