SketchUp has a relatively little-known feature that often helps when it comes to making roofs with lots of pitches: Intersect Faces. Here’s what you need to know about this terrific little tool:
Intersect Faces makes new geometry from existing geometry. It takes faces you’ve selected and creates edges wherever they intersect. Perhaps you want to make a model that’s a cube with a cylinder-shaped chunk taken out of it. You’d model the cube and model the cylinder.
After positioning them carefully, you can then use Intersect Faces to create edges where the two shapes’ faces come together. After that, you’d use the Eraser to get rid of the edges you didn’t want — the rest of the cylinder, in this case.
Intersect Faces and the Eraser tool go hand in hand. Anytime you use Intersect Faces, you need to follow up by deleting the geometry you don’t want. This isn’t a bad thing, but it does mean that you need to be good at orbiting, zooming, and panning around your model. You also need to be handy with the Eraser.
Most of the time, choose Intersect Faces with Model. This tool has three modes, but the majority of the time, you use the basic one. Here’s what all three modes do:
Intersect Faces with Model: Creates edges everywhere your selected faces intersect with other faces in your model — whether the other faces are selected or not.
Intersect Faces with Selection: Only creates edges where selected faces intersect with other selected faces. This is handy if you’re trying to be a little bit more precise.
Intersect Faces with Context: This one’s a little trickier: Choosing this option creates edges where faces within the same group or component intersect; that’s why it’s available only when you edit a group or component.
Intersect Faces doesn’t have a button. To use it, you have to either
Right-click and choose Intersect Faces.
Choose Edit→Intersect Faces.
