Tangent to Bezier curve

I have drawn a Bezier Curve or BSpline curve.
How can i draw a tangent to Bezier curve or BSpline curve?

For BSpline Curve : I have used method GeomAPI_Interpolate::Load(initialTangent,finalTangent); method but nothing happens.

For Bezier Curve : I have used LProp_CLProps::Tangent(gp_Dir) but I get compiler error as - 'LProp_CLProps' : undeclared identifier

Thanks in advance.

-Komal Patil

Marco Matt's picture

The tangent in the startpoint of a bsplinecurve is the line between the startpoint and the first pole, the tangent in the endpoint is the line between the endpoint and the (last pole)-1. You can get the point of the pole by using "gp_Pnt polePointNumberX = bspline->Pole(x);"
If you want a tangent not in the start or endpoint you can create a Geom_TrimmedCurve out of the original curve form the start/endpoint to the desired tangentpoint. The trimmed curve you can convert back to a bspline curve (GeomConvert_CompCurveToBSplineCurve). So you can again create the tangent by using start/endpoint and the related pole.