As a kid, I was obsessed with Lego. Being able to take simple blocks and make them into complex structures which were just what I had in mind was a very powerful feeling. As a grown-up, I still sometimes have ideas and designs that I want to communicate, or see for myself if they might work. When that happens, I reach for Google's SketchUp.

I first heard of SketchUp six years ago, in Kevin Kelly's excellent Cool Tools newsletter (which has since evolved into a blog). It was described as "the opposite of CAD," meaning, a very quick way to sketch out an idea and work out the details later. Back then, it was a commercial product costing $495. But then Google bought SketchUp--and its maker, @Last Software--and released a free version, and kept on making it even better.

Today, Google uses SketchUp as an important element of Google Earth: The 3D buildings you see all over the globe were made by Google Earth users working as volunteers and using SketchUp to create models of their favorite landmarks--crowd-sourcing at its best. The work of these volunteers is very much needed, as can be evidenced by these surreal bridges rendered on Google Earth.

Working with SketchUp often feels like drawing on the back of a napkin, aided by a powerful computer. Want to make a platform? Just make a rectangle and "pull" it out--voilà, it goes 3D. Need it to be in a particular height? No problem, just tap in the exact measurement on your number pad and hit Enter. Making a hole in a shape is as simple as drawing another square on its surface and "pushing" it in.

When you first start using SketchUp, an Instructor window pops up with animated guidance and quick tips for every tool you select. This is a very lightweight form of documentation: Not a lengthy dissertation on each button, but just a few quick words along with a basic animation showing what it does. This makes getting started with SketchUp even easier. Once the animation gets distracting, you can simply close the Instructor window.

SketchUp makes heavy use of inference and artificial intelligence. If you make a circle (to pull into a pole shape, for example) and then wish to make another circle around the same center point, SketchUp will just snap to the center-point of your existing circle as soon as you bring your mouse close to it. There are lots of other points the cursor could snap to--this is a complex computational task made to look simple by SketchUp's intuitive interface. SketchUp documentation even goes so far as to say that the inference engine "can get distracted" and offers tips to get it to snap to center points.

It is very likely that whatever you're trying to draw has already been drawn before--or at least something similar to it. SketchUp's 3D Warehouse is a public collection of thousands of free models ranging from a toothbrush to the Colosseum of Rome. All of these models are instantly available (and searchable) from within the SketchUp interface, so if your design calls for a chair, you can quickly pull one in from the Web rather than make it from scratch. This makes working with SketchUp even more similar to playing with Lego.

All in all, SketchUp is a phenomenal application, and a great way to bring your ideas to life or recreate your favorite landmarks and share them with the world.

Note: The Download button takes you to the vendor's site, where you can download the latest version of the software. On June 1, 2012, Trimble announced the acquisition of this software from Google.

--Erez Zukerman