title: Proper density functions for Voxel-based terrains?
body: <p>I've managed to implement the Marching Cubes algorithm in C#. Up to now I've tried the algorithm to render a sphere. That's an easy one because the density function is not very complex to code.</p>
  
  <p>But now I want to get the algorithm to go further and render some interesting terrains for games. So I would need proper density functions for this task.
  First thing that comes to my head is a Volumetric Perlin Noise. That's ok but I am looking for a terrain without convex shapes, I mean, no caves and similar geometries by the moment.</p>
  
  <p>Ok, I know that for that a simple height map can do the job, but I want a voxel-generated terrain. What type of density function o pseudocode would I need to implement them?</p>