In order to combine rugged terrain and abuttals efficiently and accurately in current GIS, an improved method is
presented which realized abuttals rendering on rugged terrain by the way of combining buffer object and ZP+ algorithm
which comes from Z-pass. We create the shadow volume via extruding abuttal data, then play real-time
rendering ,determine the width of shadow volume dynamically using screen-space error metric, as a result, the volume
could fit the scene closely. For improving the render rate we store the volume vertex arrays using buffer object.
Experiments indicate that the method advances the program performance, combines abuttals and terrain closely and
meets the demand of display.