Making sand dunes

[NuttyMonk]

Hi all,

i've been mucking about with one of the tutorials which describes how to make terrains using only functions and i'm enjoying the one about the sand dunes.

I was wondering if anyone knew a way to make sand dunes (not the ripples in the sand) like you can see in the following pictures...

http://www.tissotfamily.com/Craig/dunes.jpg
http://www.mrdowling.com/611sahara.jpg
http://www.desertvoice.org/Desert/Image/Desert10.jpg

I have been trying to make some using the perlin ridges or perlin billows power fractals but am not having much luck.  I especially like the first and second pics and the way the dunes look in them.

If anyone has any ideas, i'd love to hear them.

Cheers

[RealUser]

Hi,
if you own WorldMachine this file could be helpful: http://www.ashundar.com/datas/users/1941-dunes.zip
Another good start is the tutorial about pyramids, dunes and stuff here: http://forums.planetside.co.uk/index.php?board=6.0