[R-sig-Geo] transforming a 3d SpatialGridDataFrame into a mesh of some kind

[Mark Connolly]

I have a 3d SpatialGridDataFrame I created using krige (IDW).  I am 
using rgl facilities to create an interactive plot of the points, but 
I'd really like to have something more volumetric than points.  My copy 
of the truly wonderful Applied Spatial Data Analysis with R (shameless 
pander) is pretty mute on 3d.  Any hints on where I might find something 
on transforming the points into a mesh?  Something I need to code for 
myself?