I have a simple dust particle playing and spawning at 20 and under the shader complexity it’s white.
When I place it in my test level it looks like the level is culling the particle (reducing it) to maintain frame rate.
The material on the particle is very basic, a simple SubUV texture that is additive.
On UDK 3 the performance was WAY better as I could generally spawn 30 to 50 on this type of particle with no real performance hit.
I’ve tried reducing the spawn count to 5 which takes care of the issue, but of course the effect looks horrible at that rate.