Finally a Water-Tight Mesh!

Holy cow, this was harder than it should be! Shapeways keeps responding to numerous attempts to upload pieces of my model with an error stating that I have inverted normals. Yes, I understand why that might be a problem, but in a model with some 2000 faces (on one side of the car alone), some of which are extremely small, figuring out which ones are inverted is like looking for a needle in a haystack. In fact, if you look at the model with normals displayed in meshlab, it looks a little bit like a haystack!

It was time for a new free tool. So I downloaded AccuTrans 3D, which, while not free, is only $20 CAD for us Canadians, while the rest of you have to pay $20 USD (thank-you mouse guy from Regina!). We’re still in the virtually free world, but time is getting expensive. I still have inverted normals, but Accutrans enabled me to get a water-tight mesh, which I happen to know was going to be a problem at some time. Tracking down the holes in my mesh turned into the following little dance:

  • Export the model as a 3D model Google Earth (.kmz) file from SketchUp!
  • Rename the .kmz file to .zip and extract the .dae file inside
  • Open this .dae file in MeshLab and save it as .stl
  • Open the .stl in AccuTrans and choose “Tools/Check for Water-tight Meshes”
  • Now, the first hole I found was big enough that I could find it immediately. The others were tiny (but I guess still big enough to let water drip out), and the way to find them was to turn off the VCG layer, so I could see the holes, zoom in and turn on the VCG layer again so I could relate them to the model.

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