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Repairing Solid Models

Posted in 3dprinting, revit by Josh Goldstein 6 months ago

FormIt is a powerful solid modeling tool, but it can also be used to create or import geometry that is not solid. These models may look fine, but they have geometric fidelity deficiencies that will cause issues when converting the data to systems that require solid models, like Insight Energy Analysis, Revit, 3D printing apps, video game apps, and others.

In general, it's best to work with solid geometry in FormIt for a number of reasons:

  • Solids best represent real-world 3D materials and assemblies and help organize the model
  • Other applications like Revit and 3D printer apps require solid geometry
    • Non-solid objects are more prone to failure and more difficult to work with in Revit - so we generally recommend ensuring geometry is solid
  • Tools like Extrude work best with solid geometry
  • Advanced tools like Shell Solid only work with solid geometry

In FormIt, you can use the Display Watertight visual style (shortcut DW) to display watertight issues in the file. Try using it with Monotone Mode (shortcut DM) to make the lines more clear.

You'll see red lines drawn that indicate where the shape is not watertight. These edges can be addressed in a variety of ways, depending on the situation:

  • Freestanding edges not attached to anything should be deleted
  • Edges that overlap other edges should be deleted
  • Standalone faces that are 2D should be extruded into 3D solids
  • Faces inside of solids that do not contribute to the solid walls should be deleted
  • Solid-looking geometry may be missing a face or two, and once those faces are drawn, the shape is considered properly solid/watertight
    • Try using FormIt's Cover tool (shortcut CV) to try and automatically draw the face that is missing. You may need to employ a mix of Cover and manually drawing lines to get faces to appear. 

Also check the Display Back Faces diagnostic (shortcut DB), which will highlight the backsides of faces in red. Again, this is most useful with Monotone Mode (shortcut DM). These back faces should always face towards the inside of a solid, so a proper model should have no red faces visible from the outside. Some applications like Unity will ignore flipped faces like this, so they won't display at all. 

When drawing solid models, FormIt will automatically flip the faces, but you can also flip them yourself by selecting them and using shortcut FF. You can also invoke Flip Face from the context menu. 

See why solid modeling is advantageous, and how to use Visual Styles to identify and fix solid modeling issues:

Happy solid modeling!

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