Tips for Modeling on Top of Imported CAD Data in SketchUp

By Aidan Chopra, Rebecca Huehls

So you’ve successfully imported a CAD drawing into SketchUp and stripped down its style and visible layers to make it more manageable. Kudos — it’s time to start having some fun. Building a 3D model based on underlying (literally) CAD linework can be a surprisingly Zen experience if you follow one simple rule:

Keep the imported CAD data isolated inside of its own component and build your model on top of it. Don’t be tempted to use the imported edges to create faces directly.

Here are three reasons why:

  • CAD data is almost always full of gaps. Lines that should extend all the way to their neighbors are sometimes short by tiny, invisible amounts, meaning you’ll spend hours drawing edges and trying to figure out why faces won’t appear where you want them to.
  • CAD lines that should be parallel to one of the colored axes often aren’t. Think that edge is parallel to the red axis just because it looks like it might be? Not necessarily. Blithely turning imported edges into faces and then pushing/pulling them into 3D geometry is like building a house on quicksand; things get wonky quick.
  • Imported CAD drawings aren’t always flat. Sometimes different parts of your imported linework are located at slightly, maddeningly different heights. We’re talking thousandths of an inch — not enough to notice initially but certainly enough to mess up your work.

Instead of trying to use the imported edges as part of your 3D model, use them as references for new geometry that you draw on top of them. Tracing the imported geometry doesn’t take as much time as you’d think, and the result is a model whose geometry is far more accurate and predictable.