How will the newly-announced Nintendo 3DS show 3D graphics without requiring 3D glasses? One solid theory involves cameras (but wouldn't require a new machine). Another, here, involves a motion sensor in a portable, a trick the iPhone already does.

As you can see in the video, iPhone game WordFu, which we wrote about a year ago, simulates 3D with the help of the iPhone/iPod Touch's motion sensor. 3D graphics. No glasses. Exactly the effect Nintendo is now promising with the 3DS. Could a motion sensor be Nintendo's means to pull this off?

Since 2004 at least, Nintendo has been on-record about wanting a motion sensor in its portable game systems. In the past few months it's been trying to explain how its CEO was quoted in a leading Japanese newspaper about a new handheld needing to have a way to detect motion. And now, even though there is already a method — using the DSi's cameras — to show 3D graphics to players without requiring the use of glasses, it is announcing that a new DS successor, new hardware, will be the thing to bring us no-glasses 3D to portable gaming.

The motion-sensor approach would also answer many of the good questions people are now bringing up about how to do touch-screen DS gaming with graphics that appear to have 3D depth.

Nintendo has not said how the 3DS will provide glasses-free 3D. You see the theory above. It could be motion. According to Nintendo, we'll find out more by mid-June at E3.