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Class : Apprenti
Posts : 3
Registered on : 26/02/2010
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Resolution
In most cases a resolution of 320x240 is sufficient, this is capable of producing a much higher sub-pixel resolution, enough to allow accurate cursor control on a high resolution monitor. Resolutions 640x480 and above have diminishing returns and correspond with an exponential increase in CPU usage when not pre-processed before reaching the computer. Higher resolutions become more important at greater distances from the camera.
Sensor
For the same resolution, monochrome sensors can resolve finer detail much better than color sensors due to the lack of a color filter array.
Frame rate
FreeTrack uses interpolation with low frame rate video devices to improve panning smoothness. However, responsiveness is fundamentally limited to the frame rate; a 30frame/s webcam has a maximum response delay of 33.3 milliseconds compared with 8.33 milliseconds for a 120frame/s camera. To put this into perspective, a human’s reaction time to visual stimulus (finger reflex) is typically around 200ms, 30ms can be regarded as a competitive ping in online reflex-based games and an LCD monitor refresh rate is typically 17ms.
Higher responsiveness gives a greater feeling of control but since virtual head motion is amplified it can also cause it to move unrealistically fast. For this reason, some programs limit head movement speed, wasting some of the responsiveness of higher frame-rate cameras.
Angle
A wider viewing angle allows a larger tracking region when in close proximity to the camera. At further distances a wide angle is not desirable, more of the frame is unused and the effective resolution drops more rapidly. More peripheral light can also be seen which can interfere with tracking. Viewing angle can be reduced by using digital zoom at the cost of resolution.
CPU usage
The Nintendo Wii Remote effectively uses no CPU, NaturalPoint cameras use a small amount and general video devices can use a significant amount depending on the brand and the specific camera settings in use. A Playstation Eye running at the same resolution and frame rate as a TrackIR 4 would be very demanding on a single-core CPU. However, modern multi-core CPUs are making this less of an issue. Resolution and frame rate can always be reduced to conserve CPU resources.
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