message: Use Eigen's definition of pi for cross-platform compat
diff: @@ -102,7 +102,7 @@ namespace util {
  /// Computing the alpha value for a step in the one euro filter
  /// for any scalar type.
  template <typename T> inline T computeAlpha(T dt, T cutoff) {
  - auto tau = T(1) / (T(2) * M_PI * cutoff);
  + auto tau = T(1) / (T(2) * EIGEN_PI * cutoff);
  return T(1) / (T(1) + tau / dt);
  }
  