Hi!
Im trying to create sand/grains similar to pixars sand in piper:

The tech of PIXAR part 1: Piper – daring to be different [www.fxguide.com]

I started off with vellum grain, and simulating it falling onto a displaced surface. I just want to render a singe frame, so i dont need any animations.
Now i would like to instance grain like geometry to the particles instead of rendering it as particles in Redshift. Im new to RS, and never used instancing before.
Do i somehow have to instance my geometry before caching the simulation? If i do it afterwards, i wouldnt have the right collisions for the geometry, right?

Is there a better solution then using the Grains? I think im making a misstake here. Some help would be really appreciated! Thanks.

If the geometry you're going to instance to those sand grains is roughly spherical in shape, you can just use Copy to Points to copy whatever you want directly onto the cached vellum grains. Vellum grains have f@pscale and p@orient attributes that the Copy to Points SOP reads automatically and applies to the transform of each copy. Just make sure you pack the geometry or you're going to be waiting a while. Redshift supports packed primitives so you don't have to do much else to get it to work.

If you need super-accurate collisions at the macro level, you might need to do your “hero” sand grains using the Packed RBD solver, and then use the Vellum grains for the background elements.