I have a volume emitter set to cloud s/w for the particle type. I have an opacityPP attribute set to use a ramp for the opacity which is using a value of 0 at birth, 1 somewhere in the middle, and 0 at death. When playing my simulation in the timeline, the opacity appears to be working properly in a shaded viewport.

I have a fluid texture applied to the particles.

When I render in mental ray, the opacityPP seems to be ignored and the texture is rendering from birth even though the particle opacity is at 0 at that point.

Can anyone shed some light on this problem?

Thanks!