Newbe Dev Stack

Answer : I have tried this before, using an Avago sensor harvested from an optical mouse. It doesn't work. The resolution is excellent but the accuracy is terrible. And the calibration varies with distance from material to the sensor. I arranged a test with a 3" diameter wheel and the sensor reading the outside "tread" of the wheel. I also put a flag on the wheel, passing through an optical interrupter sensor. The number of counts read per revolution varied by a few tenths of a percent, nowhere near good enough repeatability for machining. I guess you could use the optical mouse sensor in combination with an accurate but low-resolution sensor to fill in the in-between points. But really, I think other sensor technologies are more appropriate for this. Neat idea. I considered using a hacked Livescribe pen with special dot rails for the same purpose, then an absolute location would be provided, rather than the relative location a basic optical mouse wou...

Answer : The others have already provided good explanations, but since it sounded like an interesting question and I already sketched up a diagram, I thought I would show it, too. As already mentioned, if you have an object that is to be shown as the exact same distance as the distance between you and the screen, it's very easy to represent that: It's just a single object on the screen that looks the same to both eyes. If, on the other hand, you want to show an object which is far away, then you need to 'trick' your eyes by showing two separate images on the screen, one for the left eye and another for the right eye. That's indicated by the two hollow green dots on the screen on the diagram below. And if you want to show an object which is closer to you than the actual screen distance, then to trick your eyes two images at the locations of the hollow blue dots need to be presented on screen. Note that for objects that are to appear closer than the screen distance...