Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: YuriCastroDev

rocketpy/mathutils/function.py

@@ -830,7 +830,7 @@ def __get_value_opt_nd(self, *args):
         min_domain = self._domain.T.min(axis=1)
         max_domain = self._domain.T.max(axis=1)
 
-        if hasattr(self, "_nd_triangulation"):
+        if self.__interpolation__ == "linear" and hasattr(self, "_nd_triangulation"):
             extrap = self._nd_triangulation.find_simplex(args) < 0
         else:
             lower, upper = args < min_domain, args > max_domain