Procedural Cracked Hole Material

I want a way to generate procedural cracks like in the pictures below: (more in imgur album)

I’ve been trying to do it with Voronoi textures, but have so far been unsuccessful:

Does anyone have ideas for how to do this?

I cannot offer a full solution but maybe a step in the right direction:

voronoi_fissures_1_v01.blend (122.7 KB)

  1. I used a 2D voronoi map set to “distance from edge”
  2. a radial gradient (the “length” node) to control the mapping of the voronoi distance output to black and white values, creating the hole in the middle and the tapering of the fissures towards the outside. The last mapping node just fades everything to white outside of some radius
  3. I distorted the texture coordinate input with a noise node

I used a radial gradient map to co