How do you create a heightmap files from a terrain that you''ve made using 3d modelling tools? I''ve tried to render my terrain (MAX) from the top view into a greyscale BMP, but the result is not satisfying as it doesn''t reflect the heightmap. How do you guys do it ??

Thou shalt not crosspost.

It should work fine that way ! (well it worked for me at least)
ANywayz you might want to consider creatin BMP-s with photoshop or something.
I myself like to use Paint Shop PRO 7 for heightmaps.
Just use a few gardients and some colors, convert to greyscale and there ya are

You need to get the depth-map of the top view. This can be roughly simulated by having a light where the camera is, but I''d still use a proper editor.