diff --git a/EGkSurfTriMesh.h b/EGkSurfTriMesh.h
index d7f4f68..8fdbe3d 100644
--- a/EGkSurfTriMesh.h
+++ b/EGkSurfTriMesh.h
@@ -75,6 +75,7 @@ class __declspec( novtable) ISurfTriMesh : public ISurf
       virtual bool GetFacetNearestMidPoint( int nF, const Point3d& ptNear, Point3d& ptMid, Vector3d& vtN) const = 0 ;
       virtual bool GetFacetCenter( int nF, Point3d& ptCen, Vector3d& vtN) const = 0 ;
       virtual bool GetFacetNormal( int nF, Vector3d& vtN) const = 0 ;
+      virtual bool GetFacetArea( int nF, double& dArea) const = 0 ;
       virtual ISurfTriMesh* CloneFacet( int nF) const = 0 ;
 } ;