Reduce Contour Vertices

Contouring and smoothing often creates an explosion in file size due to the many vertices it adds to the individual contour polylines. Fortunately, many of these vertices are very close together, some of which can be removed with no visible effect on the contour polylines themselves. Reduce Contours Vertices can reduce the total number of vertices up to 90%. This has the benefits of a smaller drawing file, faster drawing loading, and faster regens.

This command removes vertices in a polyline that are within a user specified offset cutoff. The algorithm looks at three vertices at a time, and calculates the distance between the second point and the line from the first to the third point. If this distance is less than the user specified cutoff, the second point is removed. In theory, reducing the polyline vertices should not shift the polyline more than the user's cutoff distance. The default for this cutoff is one tenth of a foot. Increasing the cutoff will remove more vertices while decreasing it will more closely preserve the original contour line. When combining vertex reduction with smoothing, it is suggested to smooth before reducing, although it can be done the other way around.

Prompts

Enter the offset cutoff <0.1>: .3
Select polylines to reduce. select polylines
Select objects: press Enterto conclude selection
Processed polylines: 1
Total number of vertices: 1125
Number of vertices removed: 939

Before Vertex Reduction

After Vertex Reduction

Pulldown Menu Location: Surface >> Modify Contours
Keyboard Command: reduce
Prerequisite: Polylines (contours) with vertices to reduce