isFinite(x) provides a reliable way to determine if x is a "normal" floating point number, meaning not a NaN or +/- Infinity.

This routine is specialized for all SimTK scalar types: float, double, std::complex<P>, SimTK::conjugate<P>, and SimTK::negator<T>, where T is any of the above. For complex and conjugate types, isFinite() returns true if the real and imaginary parts are both finite.