DEADSKINS: Bat Particle
I created a mask from footage of bats in Adobe After Effects in order to have bats that would actually look like they were flying as opposed to using static images. Using Bink Video I then made an animated texture that could be imported into UDK, and then made into an animated material/shader.
After studying videos of bat colonies, I got a rough idea for the acceleration and velocity settings in the particle editor. Most of the other settings/modules here were set to personal preference (they do not affect the end result to much). The most important modules in this particle are the point attractors. (SEE BELOW)
Point attractors act like centers of gravity, and by setting two next to each other the sprites gravitate between both causing the "swirl" effect.