You can't usually spin, stretch and otherwise manipulate virtual objects all that easily. You're often relegated to clicking and dragging on a mouse, and even exotic approaches like HoloLens or VR headsets introduce issues like lag. However, North Carolina State University has developed a simple solution that only requires a webcam and a little geometry. Their Captive technology revolves around a color-coded cube that sends visual cues to video recognition software -- all you have to do is rotate the cube to examine a virtual object, resize it or change textures.
It's intuitive, as you can see in the clip below, but it's also extremely quick. There's no significant latency to make you second-guess your moves. And since Captive works with any device that has both a camera and a decent amount of computing power, you could use it on everything from your laptop to your smartphone.
A practical implementation of Captive is likely some ways off, since that would require both a mass-produced cube (the existing object is 3D-printed) and integrating support into apps. However, this is one of those why-didn't-we-think-of-this-sooner discoveries that could easily find its way into 3D modeling tools, games (there's a whiff of PlayStation Move to it) and other software that could benefit from quick and easy 3D control.