3d mesh generation

Could you tell me why this happened always when I tried to make 3D mesh from 2D mesh?
I just use DEM and set the identical pixel size between mesh and the dem.
please just let me know the reason and how to solve it. ASAP

Hi Peter,

which command (i.e. exact command-line) did you use for the conversion?
Or did you use the Data Explorer?

Without seeing your input data it might be hard to judge what went wrong.

In your screenshot it looks like the elevation does not even point in the z direction, which is pretty strange.