TouchTool.SetFilterParameters Method
Sets parameters on the filter that Carmenta Engine uses to reduce jitter on touch input.
SetFilterParameters(System.Double minCutoff, System.Double beta)
Sets parameters on the filter that Carmenta Engine uses to reduce jitter on touch input.Syntax
public void SetFilterParameters (
System.Double minCutoff,
System.Double beta
)Parameters
Minimum cutoff frequency for the filter, in Hz. Determines the amount of slow speed jitter.
Beta constant. Determines the amount of high speed lag.
Remarks
The position of a touch point is not as exact as the position of a mouse pointer. Its accuracy depends on both the hardware itself and the pressure of the finger in contact with the touch surface and this means that the position usually contains a lot of noise/jitter.
Each touch tool in Carmenta Engine filters touch input to get rid of most of the noise but it is possible that the default filter does not work well with every multi-touch input device. If this is the case then an application can call SetFilterParameters on a built-in touch tool to modify the filter parameters.
The following procedure shows how suitable parameter values for the built-in StandardTool can be found:
Set minCutoff to 1 and beta to 0.
Pan at a very slow speed and observe the amount of jitter. Decrease minCutoff until the jitter is acceptable.
Next, pan quickly in different directions and observe the amount of high speed lag. Increase beta until the lag is acceptable.
Note that the minCutoff and beta parameters have an easy to understand relationship to how the filter works, decreasing minCutoff decreases the amount of slow speed jitter and increasing beta removes high speed lag.
To give you an idea of the magnitude of each parameter, the default values which have been tested on both desktop multi-touch screens and high DPI Android devices are: minCutoff = 0.0001 and beta = 0.025.
Platforms
Windows, Linux, Android