Waldo,

I don't have ZBrush so I can't really say how many polygons it would generate with its alpha. If you're using the suggested technique for rendering ZBrush objects, the level of subdivision in the VM controls the number of polygons. Grooves won't add any polygons, but might add vertices depending on your smoothing level.

I have thought about doing a rendertime displacement plug-in (like ZBrush), but currently don't have any solid plans to pursue it.

Regards,
Eric Winemiller
Digital Carvers Guild
3D plug-ins for Carrara
http://digitalcarversguild.com

Eric Winemiller
Digital Carvers Guild
Carrara and LightWave plug-ins