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Top Tip: Houdini Fracturing

19 December 2017
This week’s Top Tip comes from one of our Lead Artists, Graham Collier!Here are a few methods that we use for pre-fracturing geometry before a rigid body simulation. I have included the Houdini scene file to help you get started, and you can also download the latest non-commercial edition of Houdini from here.

  1. The simplest method of fracturing geometry is to scatter points on the surface of your geometry and then plug these points into a Voronoi fracture node.
  2. A better method, if you want nicer internal fracturing, is to use an ISOoffset node to convert your geometry into a volume and then you can scatter your points into this volume. You can then plug these points into your Voronoi fracture node.
  3. If you want to create long fragments like wood splinters you can do this by simply adding a scale node before the fracture and then shrink the geometry along one axis. Then you invert this transformation afterwards.
  4. If you want more interesting fractures then use the Voronoi fracture points node. This lets you create controlled areas of detailed fractures. Each point going into the node will create multiple points within a fracture radius. Switch on Visualise Points to see the point clusters before you fracture the geometry.
  5. Adding displacement to your geometry before fracturing will help break up the straight lines that Voronoi makes. You can use a rest node to save the original point positions and then add noise with a pointvop or mountain node. After the fracturing you can move the points back to their original non displaced positions by binding the rest Attribute back to the position in a pointVOP.
  6. Use interior detail on the Voronio fracture node to create more interesting internal detail to your fractured geometry.

And here’s a video showing you the fracturing in action: