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Using FormIt to get SketchUp data into Revit

Posted in revit, education by Tom Vollaro 4 months ago

ormIt's SketchUp importer supports the latest SKP file format including layers, groups/components and materials. Because of this, FormIt can be used as a "pre-flight" tool for preparing SketchUp data to become something more BIM-like in Revit. Be warned, as the old adage goes: "Garbage in, garbage out." SketchUp models need a certain level of fidelity and cleanliness to successfully get the geometry into Revit.

In part one of our new FormIt Workflow series, I walk through an example to see how FormIt can be used to inspect and prepare a SKP file to enter the world of BIM. If you would like to follow along, download this house from the Warehouse.  The rest of the datasets can be found here.

Here are a few rules to remember when working with SketchUp data:

Beware of Huge Files

Rule of thumb: Anything larger than 100 MB, you should consider breaking up into mulitple models BEFORE importing into FormIt. In some cases, even files of smaller size are more complex and may need to be split into smaller pieces.

 

Faces May Not Be Flat

You may notice a message in FormIt when importing SKP files that tells you some faces in the model may have been unexpectedly faceted. This is simply because FormIt has a much higher dimensional accuracy than SketchUp, so some faces that look flat in SketchUp are actually not mathematically flat. This message is just for your information. If you don't intend to edit the faces, they probably look correct and may not need to be modified. But as you work through your model, if you discover facted faces you want to extrude or otherwise modify, you can use our handy Flatten tool to make them actually flat. See this video for more detail

 

FormIt Groups = SKP Groups and Components

Components and Groups from SketchUp convert into FormIt as just "Groups" - which act like SketchUp Components, with nesting and instancing abilities. Remember to use the H key when editing Groups, to hide the rest of the context geometry so you can see only what is inside the current Group.

When preparing to import into Revit, you can re-categorize Groups as Mass, Furniture, Generic and a number of other Revit Categories.

 

SketchUp Model Watertight Cleanup

It is best to work with solid geometry in FormIt for a number of reasons:

  • Tools like Extrude work best with solid geometry
  • Advanced tools like Shell Solid only work with solid geometry
  • 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
  • Solids best represent real-world 3D materials and assemblies and help organize the model

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
  • Geometry that is nearly solid may just be missing a face or two, and once those faces are drawn, the shape is considered properly solid
    • 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 covering solid models, FormIt should automatically flip the faces, but you can flip them yourself by selecting them and using shortcut FF. You can also invoke Flip Face from the context menu. 

See this Screencast showing how to use Monotone Mode, Display Watertight Issues, and Display Back Faces diagnostics in conjunction to correct a simple SketchUp model that exhibits all of these issues. 

 

SketchUp Texture Overrides

SketchUp allows material textures to be manually scaled, skewed, rotated, or moved on a per-face basis. FormIt respects these overrides when importing SketchUp models, but unfortunately, Revit will discard them, so it's best to avoid them when sending models to Revit.

If you notice materials losing their scale in Revit when compared to FormIt or SketchUp, you can check for per-face overrides in SketchUp by right-clicking the face, hovering over "Texture" and seeing if the "Reset Position" option is available. If so, this face has overrides which won't transfer to Revit.

Instead of overriding the texture per-face, it's best to adjust the texture definition itself to match the desired scale, rotation, or position. This might mean making multiple texture definitions if the material texture was previously overridden in multiple places in the SketchUp model.

 

Export Only What You Need

Finally, and most importantly, use Export Visible or Selected to save your model into multiple smaller FormIt (AXM) files before importing into Revit. Alternately, you can select geometry from inside a Group, launch a new window of FormIt, and Paste in Place (Ctrl + Shift + V) to get the geometry to appear in the exact location, but in a clean file. Then you can export geometry from the clean file - this ensures the origin point is maintained (especially when exporting nested geometry whose parent group might have a different origin than the world origin), and also allows you to do operations like ungrouping or joining shapes without affecting the original geometry. This will save a lot of time in the end, and allow you to narrow down problem areas when you get errors on import.

 

 

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