Длина и угол Spline

1)

virtual Acad::ErrorStatus
getDistAtParam(
    double param,
    double& dist) const;

param    Input parameter specifying a point on curve
dist    Returns the length of the curve?s segment from the curve?s beginning to the point specified by param
Calculates the length of the curve?s segment from the curve?s start point to the point specified by param.
Returns Acad::eOk if successful, or Acad::eInvalidInput if param is out of range. For other errors, the implementor must decide what return value to use. See the acdb.h header file for possible ErrorStatus values.
In the default implementation, the function returns Acad::eNotImplemented.
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2)

Acad::ErrorStatus
getFitPointAt(
    int index,
    AcGePoint3d& point) const;

index    Input index (0 based) value
point    Returns fit point (in WCS coordinates) at index
Returns with point set to the value of the fit point at position index.
Returns Acad::eOk if successful, otherwise Acad::eGeneralModelingFailure is returned (for example, if the spline doesn't have fit data or index is greater than the number of fit points in the spline).
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Acad::ErrorStatus
getFitTangents(
    AcGeVector3d& startTangent,
    AcGeVector3d& endTangent) const;

startTangent    Returns start point tangent vector (in WCS coordinates) of spline
endTangent    Returns end point tangent vector (in WCS coordinates) of spline
Returns with startTangent and endTangent set to the start point and end point tangent vectors in WCS coordinates.
Returns Acad::eOk is successful, otherwise Acad::eGeneralModelingFailure is returned (for example, if the spline has no fit data).
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