When you’re building a model of something, not everything will have squared edges… the top of a table for instance might be rounded off edges, or a picture frame would have a fancier curve to its edges. (For anyone familiar with woodworking tools, think routed edges. For web developers, border-radius!)
To accomplish this in SketchUp, you will need a tool called “Follow Me” and a little out-of-the-box thinking. The process is simple once you know it, but might seem a little strange at first. To begin, you would simply create the original shape, complete with 90 degree sharp edges. In our example, we’ll make a box with a rounded top. Here’s what we’re going to aim for:
To get there, lets build the box with normal square edges. (If you need a refresher on the basics, see Trimble SketchUp 101.) Draw a square, then push/pull it into a cube.
Now we want to round off the edges. Start by selecting the Draw > Arcs > 2 Point Arc tool. Begin the curve mid-way down an edge, end it in the middle of the top, and round it out towards the corner (making sure not to extend past the edges)
Now select Tools > Follow Me and point to the outside of the arc you just drew. Click in that area, and drag it along the edge. This will delete any material along that edge, making it the same curve as the arc.
Now change back to the Select tool, click on the arc and its neighboring line segments, and delete those.
Repeat the same process with the other side of the box lid, to make a rounded lid on your box.