That means, that you have moved the vertices in all axis (x, y, z) while modeling. Convert to hmp only work if every vertice only moved up or down.
HMP is like MDL. But hmp "models" are only sculpt in z axis. If you make a plane and pick one vertice, than you must move it up or down. But not to the right or left. Then after export it should be work.
Hope this helps. Otherwise you can youse the model as terrain too.
Last edited by Schmerzmittel; 07/10/09 00:00.