Can I use an material texture to represent a surface of spheres? I can cover a ball object in particle spheres but this is very processor and memory intensive. 



I was wondering if I can use the new voronoi textures in Blender 2.82 to make pseudo spheres around the surface? Obviously it won't achieve the depth effect shown balls image attached.

I'm not sure if I can fake a surface displacement with Dot-product to an emission shader or use displacement in Cycles? I would be keen to try an Eevee normal displacement if its good enough.

Currently I cannot get Voronoi texture to represent moving balls very well.
Use a texture to drive a bump node. Plug Bump's "normal" output into the normal input of the Principled BSDF node. I can make a voronoi texture small enough to represent closely packed balls or bubbles. Then I can colour them as a group with a noisy texture. This hides the fact that each ball is not really coloured. Finally I use a 4D texture to animate the bubbles motion over time.



Here are the nodes :