How to get length of curve in OpenCASCADE

OCCUtils provides a convenience function to get the length of a curve in OpenCASCADE:

#include <occutils/Curve.hxx>

using namespace OCCUtils;

GeomAdaptor_Curve curve = /* ... */;

double length = Curve::Length(curve);

You can call it with GeomAdaptor_Curve or Geom_TrimmedCurve. While you can also call it with Handle(Geom_Curve), this is usually not what you want to do, since Geom_Curve typically describes an infinite curve (like an infinitely long line) and doesn’t know about which section of the curve is actually use (GeomAdaptor_Curve and Geom_TrimmedCurve both have the required Umin/Umax information stored).

In case you need to do it manually (without OCCUtils), use this snippet:

#include <GCPnts_AbscissaPoint.hxx>

GeomAdaptor_Curve curve = /* ... */;

GCPnts_AbscissaPoint::Length(curve);

For a Geom_TrimmedCurve, you need to convert it to a GeomAdaptor_Curve first. See How to convert Geom_TrimmedCurve to GeomAdaptor_Curve in OpenCASCADE for details on how to do that.