vray rendering of sandbox topography

[winata]

Hi all,

I've been trying to apply material to the lofted topography surface from contour lines using the "from contour" sandbox tool. It doesn't seem to want to show the vray material once I render. The lofted surface comes as a group, and even though I've applied material to the group and within the group, it does nothing. Why does this happen and how can the material show up?

Thanks!!