UDK Fog Volume Falloff

cozzbp

I am working on making a very large forest for an environment, and I can't seem to find a way to make fog volumes have a falloff. Inside the fog, I really like the effect, but outside the fog, there are very clear borders. I can't do an exponential height fog, because I only want the thick green fog inside the forest itself. Any ideas on how I can get a fog volume to fade slowly? Thanks.

Visceral

Why fog volumes? Use exponential heighfog instead.

cozzbp

Well, exponential heightfog would be nice if I could limit it to a certain area. I only want that thick fog in that region of my map (and my map is huge). So is there a way to limit the range of exp. heightfog and have multiple of those? Thanks.

mcbrightside

If the fog volume's material uses a DepthBiasedAlpha property you should be able to adjust the curve the texture fades at when it intersects another object (which in this case would be the ground). Maybe see if you can tweak the material.

Hourences

That probably would not work because that only fades out where it intersects geometry so you would still have a sudden cut off in the open air as in that screenshot.

Your best bet is a custom UV'ed fog volume staticmesh, that has a gradient texture applied so it fades out in open air, or perhaps "easier" would be to use Exp Heightfog and then change the density of that client sided via a Trigger - Matinee. You can animate fog values via Matinee, so you could have when in trigger -> smoothly transition to denser fog values, when step out -> reverse animation.
Coupled to that would be a fogplane, large single camera facing sprite particle, or some kind of box mesh that only fades in when at a distance, to ensure that when viewed from a distance you'd still see fog in that area. That material would basically just be a Pixeldepth to control fade over distance + DepthbiasedAlpha to ensure fade on intersect + fog color + a nice gradient texture to ensure smooth fade out on its edges.

Something in that direction is what I would try.