A friend of mine is pretty much obsessed with papercraft. Over the years he has built many beautiful models and I really like the aesthetic of this white, minimalistic and precisely folded paper geometries. He always starts by modeling them first in Blender and when he’s satisfied with the shape he uses Pepakura to unfold it to a plane so that he can actually build it out of paper. Pepakura is a simple yet powerful small program and can unfold pretty much everything into a foldable pattern. I found it quite fascinating and so I thought it might be a good idea trying to implement something like this in Houdini. Not that I’m building much paper models but nevertheless it’s sometimes useful to unfold meshes. After some research and several tests it turned out to be actually quite easy. And after some more test I finally implemented a simple version of an unfolding algorithm in VEX. Basically it works as follows:

  • Build the dual graph of the mesh
  • Calculate a spanning tree to minimize cuts and prevent faces from overlapping
  • Cut the spanning tree
  • Unfold mesh