Shadow casting invisible objects?

[cybernoid]

Hello,

We are using proxy meshes with a subsurface scattering specular material derived from Karba's clouds example. We position them in roughly the same place as a FumeFX render that we will composite on top.

However we need to turn off the rendering of the clouds surface but still keep their scattering/shadowing effects on the scene to composite correctly. Setting the cloud proxy objects in 3dsmax to be non-visible and still cast shadows etc doesn't work.

Is there anyway to do this currently? If not we definitely need the ability to do this for lots of stuff in the future also.