Read a very insipring article on how Pixar managed to create the realistic sand in Piper. Decided to have a go in Houdini and see what results i could achive with packed geometry.
Very pleased how it turned out. 3 milion is about the maximum i could achive with my current computer. This takes about 13gb of ram at render time so decided to not push it much further on my current 16gb setup, 

Rendered in Mantra using custom attributes to drive roughness, IOR, and color. Three separate materials for diffuse/glossiness, SSS and refractive rocks were used in order to create some randomness. I used three separate rock models at about 500 polygons each as well.

Instaning only happens within the camera frustum and I used the same method to drive density based on distance to camera. This way the area I wanted to focus on had a higher density than the background rocks.


Color represents the area where instancing happens and how density is higher the closer the rocks are to the camera.