I have a polyline element and I want to reduce the number of points (vertices?) that make up the line. I know it will make the curved sections jagged and that is fine. I just want to control (perhaps by a percentage of the total?) how many points are decimated. I looked at the ITopologicalOperator.Simplify method but this does not seem to be what I need.
Take a look at IPolycurve.Generalize or IPolycurve.Weed methods. Both use a specified maximum offset tolerance. If, however, you need to specify how many points are decimated, you can make several passes over your geometry, using Generalize/Weed to reduce the vertex count, keeping track of this count until you are happy with the results.