So sorry we left you hanging with our last post, but it took us longer to get packed than we anticipated. So thanks for waiting patiently. But with coffee in hand, we are now ready to hit the road to the Land of 3D Air Mice. Our first stop along the way is the venerable PC mouse since computer mouse dynamics provide the underpinning for today’s 3D air mice.
Believe it or not, the first mouse prototype was developed way back in 1963 by U.S. inventor Douglas Engelbart working at SRI International. It was wooden and had two metal wheels. Engelbart first called it an X-Y position indicator for a display system. Then he and his team had the better sense to call it a mouse because, well, it looked like a mouse.
The first public demonstration of the PC mouse was held in December 1968 at what is now known as the Mother of All Demos. The SRI team showcased videoconferencing, hyperlinks, text editing, networked collaboration and of course the mouse. (There is no truth to the rumor that Engelbart also demonstrated Facemash which is a lie propagated by the Winklevoss twins. Ok, we just made that up.) If you have a historical interest, you can find videos of the public demonstration here.
So that’s great to know, but what does this have to do with our 3D air mice? Well we are glad you asked. There are two really important aspects to computer mouse dynamics that we are certain you haven’t given much thought. It’s because they work so well, you probably don’t even realize it.
First, the computer mouse provides a relative pointer. By this we mean it provides a cursor that is bound to the screen. A bounded cursor always remains visible on the screen no matter how far in any direction you move the mouse. The distinct advantage of this approach is that the cursor is always visible on the screen and never disappears, so the user doesn’t need to “find the cursor”. This approach is in stark contrast to absolute pointing systems with a fixed frame of reference. For example, try navigating the menus on the Wii. Unless you maintain pointing the remote control directly at the sensor bar, the cursor goes off the screen and now you must go hunting for it. We really love playing games but we really hate cursor hunting.
Now the challenge of a relative pointer is that you may need to re-center the mouse to use it comfortably which can be hard for novice users. For example, try this for an experiment. With your PC mouse to the right hand side of your PC keyboard, slide your mouse to the right by 12 inches. Now you can continue using the mouse over at this long distance away, but it would become cumbersome to use after a while unless you are an NBA basketball player and have arms that are like 5 feet long. So if you want to use the mouse more comfortably you now have two choices. You can pick the mouse off the table and set it down closer to the keyboard. Or you can just move the mouse back 12 inches to the left and basically use the left edge of the screen to bound the cursor on the way back. Either way will work.
As we said, children and other new users of the PC mouse often take a little time to get accustomed to this. But we are all quick learners and eventually re-centering the cursor becomes second nature. Or we become so good at it, that we rarely need to do it. But either way, the key thing is that no thought is required.
The second important mouse dynamic is non-linear ballistics. This is a fancy way of saying that the mouse velocity is not constant. When the user moves the mouse, the system measures its speed and then applies a gain to it – a multiplier. The multiplier varies depending on the speed. The gain curves are configured to apply acceleration as you move the mouse quickly (gain > 1) and deceleration as you move the mouse slowly (gain < 1). This helps in two ways. The acceleration means less effort is required to move the cursor long distances across the screen. The deceleration enables the user to more effectively hit smaller targets on the screen. The effect of this behavior is that the cursor will not always appear in the same position as the mouse moves around.
If you don’t believe us, try this experiment. Position your cursor on the left side of the screen. Move your mouse quickly to the right by 3-4 inches. (Try not to hit the right edge of your screen with the cursor.) Then move your mouse back very slowly to the left again until the cursor reaches the left edge of the screen again. We’ll bet that the mouse isn’t in the same position as when you started.
It’s the combination of a bounded cursor and nonlinear gain which makes the PC mouse both efficient and easy to use. And it’s this relative pointing feature which will form the basis for highly usable 3D air mice.
So that’s our quick trip for today! Now let’s get on the road again. We’re going to pick up some fast food and eat on the bus to save time. Next stop, we’ll learn more about the living room and important considerations for 3D air mice.