Realistic maximum slope and fuzzy zone

[MF_Erwan]

I'm looking for realistic values of maximum slope and fuzzy zone for:
-Sand (probably low max slope, but how?)
-Soil
-Grass

Erwan

[Henry Blewer]

For sands, i go by the environment I am trying to model. I use 40 to 45 degrees. I don't often use altitude constraints.
Soil tends to be flatter, it also washes down the hillside more uniformly. I think 20 to 25 degrees. Altitude is up to what your are trying for.
Grass can really be anything as far as slope. It depends on the species. It does look better with an appropriate altitude constraint.

The fuzzy zone. Sand can have a quite large one. Soil tends to be tight. Grass; it is what looks best to you.

The sands and soils look better if a compute normal is connected to the input. Use intersect underlaying, favoring depressions. A child surface layer helps give it displacement (bumpiness). The displacement should be small. Intersect underlaying is under the effects tab in the surface layer.

[Volker Harun]

This is a complex physical phenomen depending on different factors:

Fill a glas with sand ... turn it to some degree until the first bits move.
Turn it further until the sand is beginning to flow.

Repeat the same with wet sand, dry powdered clay, mud, and so on.

If you have a humid scenery your values will be different from a desert.

Volker

[cyphyr]

"Realistic" is up to you the artist, but that said the subject your asking about is (I think) the Maximum Angel of Repose, a highly complex subject I know nothing about I found quite a few complex graphs and equations that were also beyond me but I then stumbled across a list of angles. If you after an"accurate" answer  this might help.

Richard

[Henry Blewer]

Volker's suggestion is a very good one, as usual It would make guessing much easier.