Nexus One has a major multitouch problem

Android and Me has posted an interesting tidbit of information regarding the Nexus One's touch screen. Apparently, the phone seems to have a problem with following multiple touches moving across the same axis. The problem was pointed out by game developer Robert Green, who was having issues with the screen when developing for Battery Powered Games. To illustrate the issue, he made an application called Multitouch Visible Test (available in the Android Market). Here's how he describes the problem:

"This app shows how your phone's hardware handles multitouch. The event data is not processed in any way. The two dots are drawn exactly where the phone reports you are touching. For many current Android phones, there will be lots of bad data including axis flipping and near-axis influence."

Pinch-to-zoom does not seem to be affected. However, the problem does rear its ugly head in some multitouch applications, like ToonWarz. This could turn off many developers from making quality games for Android. A lot of these gestures could affect how a game that has one virtual joystick on the right, and another on the left, would operate. It would be impossible for it to work.

Google engineer, Dianna Hackborn, has responded to the issue in the Android Developer group, and it doesn't sound too good. She explains how the Droid (which doesn't have the problem) and Nexus One have different hardware sensors, causing them to react to touch differently. It's unclear if a software update would be able to rectify the issue. But, from what Hackborn says, it seems unlikely.

"Sorry I meant exactly what I said: this is how the touch screen hardware on the Nexus One works (which is essentially the same screen as on the G1 and myTouch).  The Droid has a sensor from a different manufacturer, with different behavior.  Other phones will likewise have different sensors."

Hackborn links to an explanation by Luke Hutchison, who explained the issue in depth on the G1. He discussed how the issue primarily shows up with rotation based gestures. Since most gestures that people do on phones don't require rotation, this isn't really such a big problem. He also notes that the screen gives an advantage to two-fingered, axis aligned gestures, such as sliding two fingers up and down the screen, since it locks them into alignment. Hutchison discusses a possible solution to the overall "point snapping" issue. However, according to Robert Green, the solution only works for basic gestures, and does not solve the two independent point probem.

"The system could be made more natural to use by building in motion estimation (inertia and damping) in the vincinity of the discontinuities where touch points cross over each others’ axes, so that if the user is in fact doing a rotation gesture by moving strongly towards the axis crossing point, events will continue to be generated that smoothly cross that point. Of course there is still the potential for error here though if the user stops or reverses direction."

It will be interesting to see if Google issues an official response. This "glitch" has the potential to turn away many potential Nexus One customers. Many Android phones use cheaper screens, most of which probably have the same issue. Perhaps this is the reason Google held off on multitouch gestures for so long.  This video demonstrates the problem:

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