Thanks I’ll check that out 
Looking through source, found this in InterpCurvePoint.h:
/** Computes Tangent for a curve segment */
template< class T, class U >
inline void AutoCalcTangent( const T& PrevP, const T& P, const T& NextP, const U& Tension, T& OutTan )
{
OutTan = (1.f - Tension) * ( (P - PrevP) + (NextP - P) );
}
Looks like that’s the way to do it!