Hi,
I'm exporting a fluid simulation from Houdini using a tracked camera from a match moved scene in Nuke.
The end result is a water fountain that is going to sit in a street scene in a Nuke comp.

I'm wondering though, how do I deal with water transparency? I've exported fluid sims from Houdini before, and I've always ended up with the water retaining a black background. Anything that's not behind the water is always fine and transparent where needed, but the water never seems to retain it's alpha properties.

Is there a way I can carry through this information in the render? I'm currently rendering through to Image Viewer, from then on does it make a difference which format I choose? I tend to go for Open EXR, TIFF or PNG.

Fingers crossed this makes sense.

Any help and advice would be fantastic, and greatly appreciated.
Thanks in advance guys.
Chaz