How to generate different instances of actors in a specific volume , not be a regular cubical or conical manner but rather than a spline-based volumetric space ; using Perlin-noise or what ever mechanism; where probability of spawning different instances changes based on the distance of player.. For example , there is an indie game " A game about digging a Hole " on steam, where Different types of rocks, gems and minerals are spawned within the dirt and changes based on the distance of the player.. Any tips for balanced and performance friendly suggestion is accepted..