event thresh
VRModules				                      event thresh (6)


NAME
	event thresh - a thresholding module which applies a "notch filter"
	to the input data.  This is useful for zero-ing out events which
	have rotational or translational values that fall above or
	below a certain threshold, especially in the context of working
	with noisy input devices such as magnetic trackers.


SUMMARY
     Name	   event thresh

     Type	   filter

     Inputs	   field float 1D 1-space uniform
		   (VR device event field)

     Outputs	   field float 1D 1-space uniform
		   (VR device event field)


     Parameters	   _N_a_m_e		   _T_y_p_e		  _D_e_f_a_u_l_t	 _M_i_n	   _M_a_x
		   Angular min	   float	  0.5		 0.0	   5.0
		   Angular max	   float	  5.0		 0.1	   10.0

		   Trans min	   float	  1.0		 0.0	   5.0
		   Trans max	   float	  5.0		 0.1	   10.0


DESCRIPTION
	The event thresh module applies a "notch filter" to the input
	field.  The filtered data is sent to the output port.

	For rotations, rotational values which fall below "Angular min"
	or above "angular max" are set to zero, while those values
	which are between "Angular min" and "Angular max" are not
	changed. 

	The same scheme is used for translation events.

	This module is useful for filtering out small "noise" values
	produced by noisy input devices, such as magnetic trackers.
	
INPUTS
     	field float 1D 1-space uniform - VR device event field.  A set
	of C-language macros is used internal to the code for this 
	module to encode the device event information into an AVS
	field.  This field is not readily processible (unfortunately)
	by "normal" AVS modules.  This is the case because both
	floating point and boolean values are encoded into the field data.


PARAMETERS
	Angular min, Angular max - the min and max values which define
	the width of the notch filter applied to the rotational component
	of the input VR event field.

	Translational min, Translational max - the min and max values which 
	define the width of the notch filter applied to the translational 
	component of the input VR event field.

OUTPUT
	see INPUT.

EXAMPLE
	division ipu
	    |
	event thresh
	    |
	vr xform obj
	    |
	geometry viewer

RELATED	MODULES
	event scale, button acc


VRModules					  Lawrence Berkeley Laboratory
April 1996