public double PointsPerInch {get; set;}

//Must be called on the MCT
//var pcsl = ...;
var def = pcsl.GetDefinition() as CIMPointCloudLayer;
//PointsBudget - corresponds to Display Limit on the UI
// - the absolute maximum # of points to display
def.PointsBudget = 1000000;

//PointsPerInch - corresponds to Density Min --- Max on the UI
// - the max number of points per display inch to renderer
def.PointsPerInch = 15;
//Commit changes back to the CIM
pcsl.SetDefinition(def);