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monovich
02-08-2008, 04:25 PM
Howdy,

I'm trying to make flowing sand dunes with nodes. I'm aware of using the DP node for the small surface ripples, but I'm trying to procedurally make the large flowing wind-blown hills. I'm trying to get the sharp wind lips where the side in the wind shadow has a steep falloff and the side towards the wind has a smooth falloff, somewhat like this image:

http://upload.wikimedia.org/wikipedia/commons/3/35/Dunes.jpg

I was trying to use a light incidence gradient thinking that everything in the wind shadow could be simulated by light shadow. I was hoping to plug that into the contrast of the procedural texture in order to make everything at a certain angle have a steeper falloff.

this seems in my head to be a somewhat sound Idea, but I can't figure out how to get it to work.

Does anyone have any ideas?

thanks.

-sf

grn
02-10-2008, 06:47 PM
It is extremely hard to make realistic dunes, especially barchan dunes.

If you want a fully computed solution, I suggest stretched diamond dot perlin noise. You wont get close to realism with procedurals, though. If you want realism, you need a very experienced texture artist for displacement maps.

You could also get some DEM data and convert that to a mesh with Marvin Landis' tools.

monovich
02-11-2008, 11:47 AM
grn - thanks for the reply. Sometimes just getting a reply around here can be tough.

I've made some progress on the nodal dunes. What I've got are completely procedural and pretty tweakable, they just need some work.

I didn't end up using the techniques I thought, though. I've had the most success with the FBM procedural, of all things.

Here are a few screen grabs if anyone else tries this down the road.

My challenge now is to add enough detail to just the tops of the ridges and less to the valleys, which I could do with APS if I could isolate just the tops of the ridges. The surface undulates so much it isn't easy to isolate either the slope or elevation.

Does anyone know how to generate a normalized baked displacement map from the displacement node tree? With that I could make an APS weight map I think.

I've also got to work on particles for the sand blowing over the dunes.

thanks,

-sf

GregMalick
02-11-2008, 02:18 PM
Interesting.

Could you post a screen-grab of the sand-object before the displacement?

monovich
02-11-2008, 03:09 PM
the sand object is just a 1km flat plane subdivided until most of the jaggies are gone. I got successful renders @ HD with fPrime at about four million polys, but it could be a lot lower res if I could figure out how to use APS to get detail just where I want it.

The higher the res of the mesh the sharper the peaks of the dunes will be, as it is they are limited by poly size and if the displacement gets too sharp they distort because of the resolution of the mesh.

GregMalick
02-11-2008, 07:05 PM
Now it sounds amazing.

I'm going to have to study that node setup.

monovich
02-11-2008, 07:15 PM
forgot to add that the little ripples are from Dennis' plugin and are only a bump. They are displaced along the contours of the larger dunes by plugging the large displacement info into the scale, position, rotation of the ripples procedural.