Some of users might encounter an issue, the character walks on a uneven surface with Motion Director, seems that the character will not snap to the surface automatically, or the result is not good, especially using a custom imported surface. Here below is the solution.

If the surface is not very bumpy, you can achieve this easily with Motion Director. Here is the tutorial:
https://courses.reallusion.com/home/iclone/motion-director?v=iclone-8-tutorial-getting-started-with-motion-director

Motion Director can response to the surface, 
https://courses.reallusion.com/home/iclone/motion-director?v=iclone-8-tutorial-reacting-to-surface-and-terrain-with-motion-director

You may go to MD Controls panel > Character Settings > Simulation > Click the gear icon beside [Snap to Surface] to open Surface Sensor Setting:
(Please note that in this video at 1:33, some UI layout of the panel has been changed in the current version iClone)

For your information, if the surface is too uneven, you may also try to adjust this option [Hip Elevation Smoothness] lower or higher, see if the result becomes better.