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       anim_turn - make	animation table	for vehicle with front-wheel steering.

       anim_turn -l length [-a angle] [-r radius] [-f factor] [-p integer] _
		 in.table _ out.table

       The motion of a front wheel steered vehicle is not simple - the
       instantaneous velocity of the front wheels is in	the direction they are
       pointed,	while the instantaneous	velocity of the	back wheels is the
       direction the vehicle is	pointed. The purpose of	anim_turn is to
       produce a complete animation table for such a vehicle, given a table
       specifying the desired position of the front axle at each relevant time
       step. The input table should contain four columns, specifying the time
       and 3D position of the center of	the front axle.	Actually, the path is
       assumed to be confined to an x-y	plane, but the three columns are
       included	for consistency	with other animation routines.

       The output is normally a	seven-column table which is a copy of the
       input table with	three extra columns specifying the yaw,	pitch, and
       roll of the truck at each time. The pitch and roll are always zero,
       since the motion	is assumed be in an x-y	plane.

       The -l# option is not optional, and is used to specify the length of
       the wheelbase (from the front axle to the rear axle).

	   Track assumes that the truck	should initially be oriented along the
	   line	defined	by the first two positions in the input	table.
	   Otherwise, the desired initial yaw of the truck can be specified
	   with	the -a#	option.

	   Specify the radii of	the front wheels. If this option is selected,
	   track will create an	animation script to animate the	front wheels.
	   The output table would contain four columns:	time, swivel-angle,
	   roll, and a zero channel. These represent the orientation of	the
	   front wheels, in terms of yaw, pitch, and roll, and the table can
	   be piped directly to	anim_script.

	   Specify a factor to be used to animate a steering wheel. If this
	   option is selected, the output table	will contain four columns:
	   time, swivel, and two zero columns. This table can be used directly
	   by anim_script to make an animation script for a steering wheel.
	   The argument	to the option should be	the factor by which to
	   exaggerate the swiveling of the wheels. For example,	on a typical
	   truck, you may need to turn the steering wheel 360 degrees in order
	   for the wheels to swivel 20 degrees.	To model this effect, a	factor
	   of 18 would be used.

	   Specify the ratio of	input rows to output rows, which must be an
	   integer. The	default, of course, is one. The	accuracy of the	output
	   depends on having a large number of input lines, which is not
	   usually a problem in	animations, which require a large number of
	   frames per second. However, if a test animation with	a small	number
	   of frames per second	is being created, the user should give an
	   input table with a high number of input rows	and reduce the output
	   with	the -p#	option.	For example, if	in.table contains 30 rows for
	   each	second of the animation, then the command

	   anim_turn -l	3000 -p10 < in.table > out.table

	   would produce an animation table containing 3 rows for each second
	   of the animation.

       The algorithm used only works for motion	in an x-y plane.

       Carl J. Nuzman

       This software is	Copyright (c) 1994-2013	by the United States
       Government as represented by U.S. Army Research Laboratory.

       Reports of bugs or problems should be submitted via electronic mail to

BRL-CAD				  07/08/2017			  ANIM_TURN(1)


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