This global floating-point constant is an approximation of Pi.
See Also:
IlcArcCos, IlcArcSin, IlcArcTan, IlcCos, IlcDegToRad, IlcHalfPi, IlcQuarterPi, IlcRadToDeg, IlcSin, IlcTan, IlcThreeHalfPi, IlcTwoPi