Please use the setSegmentation call, note it is now a call that is model dependent. The circleSegments(circles, smallCircles) can be replaced with

    double  segmentationLength = 0.;
    getSegmentation(model, nullptr, &segmentationLength);
    setSegmentation(model, circles, segmentationLength);


public const string ifcenginedll = @"ifcengine.dll";

[DllImport(IFCEngineDLL, EntryPoint = "circleSegments")]
public static extern void circleSegments(int_t circles, int_t smallCircles);    

Property circles

Size: 64 bit / 8 byte (value)

Property smallCircles

Size: 64 bit / 8 byte (value)