Sand-like properties

[josemendez]

I want to simulate sand. Kind of stylized. Think on Gaara sand visuals or the sand-falls from Journey game.

I'm thinking for the effect I want I should not use a granular blueprint.

Hi!

Technically, sand is a granular material: an aggregate of many very small rigidbodies. However this makes it extremely costly to simulate very fine granulars like sand. To maximize the amount of particles used to represent a granular, your best bet is to use an hybrid lagrangian-eulerian approach like MPM or PIC/FLIP, but even then it will be a prohibitively costly simulation.

How should I set the properties of a fluid blueprint to achieve the closest feel and texture.

Fluid simulation is not really suitable for granulars: you would need to have very small neighborhoods and better incompressibility guarantees, which makes it extremely costly to solve. At this point you're better off using actual granular simulation, but as stated above even then it's too costly to simulate sand. You can use it for gravel, pebbles, but not sand.

Is it possible to control the angle of repose of a fluid with obi?

No, this concept is exclusively used when dealing with granulars. Fluids do not have an angle of repose, since they're not solids and have no "rest shape".
https://en.wikipedia.org/wiki/Powder#Com...substances

A liquid flows differently than a powder, because a liquid cannot resist any shear stress and therefore it cannot reside at a tilted angle without flowing (that is, it has zero angle of repose.) A powder on the other hand is a solid, not a liquid, because it may support shear stresses and therefore may display an angle of repose.

Wrapping up: you cannot use Obi to accurately simulate a large amount of sand. If you want accurate sand, your best bet are hybrid cell/particle methods, which are still too costly unless all you have in your game is sand.

Alternatively, you could use cellular-automata. This technique is rather old, not really physically based, but extremely simple and cheap. You can see it used in most "powder-toy" like apps and some games like Noita.