After BuildGeometry is run, the ResultEdgeGeometry and ResultJunction geometries are set. These are the geometries that are drawn to the screen in the AfterDraw event. Note that the same geoemtry is used for both the edge results and the "buffer" which is not actually a buffer at all, but rather just a fat line.

'Declaration
 
Public Property ResultEdgeGeometry As ESRI.ArcGIS.Geometry.IPolyline

'Usage
 
Dim instance As TraceResultsRendererExt
Dim value As ESRI.ArcGIS.Geometry.IPolyline
 
instance.ResultEdgeGeometry = value
 
value = instance.ResultEdgeGeometry

public ESRI.ArcGIS.Geometry.IPolyline ResultEdgeGeometry {get; set;}