diff --git a/EGkVolZmap.h b/EGkVolZmap.h
index cf3a679..f03796c 100644
--- a/EGkVolZmap.h
+++ b/EGkVolZmap.h
@@ -90,6 +90,7 @@ class __declspec( novtable) IVolZmap : public IGeoObj
       virtual IVolZmap* ClonePart( int nPart) const = 0 ;
       virtual bool RemovePart( int nPart) = 0 ;
       virtual int  GetPartMinDistFromPoint( const Point3d& ptP) const = 0 ;
+      virtual bool ChangeResolution( int nDexvoxRatio) = 0 ;
 } ;
 
 //-----------------------------------------------------------------------------