Building Footprint Extrusion

[GarySchells]

Hello there,
I am now trying to create a rule to extrude my building footprints based on an attribute in the table.  My rule is as follows

/**
* File:    BldgHeight.cga
* Created: 18 Oct 2013 19:30:10 GMT
* Author:  gschells
*/

version "2012.1"

# this attribute will be sourced to the object attribute
attr RoofElevat = 0

@StartRule
Lot -->
extrude(RoofElevat)



I have assigned this rule file to my building footprints and set the Start Rule value to "Lot", but my buildings remain flat polygons.  I would appreciate any feedback.  My hope is that as I get through my project via baby steps I'll be qualified to actually answer some questions.       


Thanks

[GarySchells]

Thanks again Matt.  I re-imported and I think the buildings are extruding to correct height.