Class v LinearAttraction v

Класс v_LinearAttraction_v

/**
 * Generates a vector towards a goal location
 * that varies with distance from the goal.  The attraction is
 * increased linearly at greater distances.  
 * (c)1997, 1998 Tucker Balch
 */

package EDU.gatech.cc.is.clay;

import java.lang.*;
import EDU.gatech.cc.is.util.Vec2;
import EDU.gatech.cc.is.util.Units;

public class v_LinearAttraction_v extends NodeVec2
{
	/**
	Turns debug printing on or off.
	*/
	public static final boolean DEBUG = /*true;*/ Node.DEBUG;
	private NodeVec2	embedded1;
	private double		controlled_zone = 1.0;
	private double	        dead_zone = 0.0;

	/**
	Instantiate a v_LinearAttraction_v schema.
	@param czr double, controlled zone radius.
	@param dzr double, dead zone radius.
	@param im1 double, the node that generates an
		egocentric vector to the goal.
	*/
	public v_LinearAttraction_v(double czr, double dzr, NodeVec2 im1)
	{
		if (DEBUG) System.out.println("v_LinearAttraction_v: instantiated.");
		embedded1 = im1;
		if ((czr < dzr) || (czr<0) || (dzr<0))
		{
			System.out.println("v_LinearAttraction_v: illegal parameters");
			return;
		}
		controlled_zone = czr;
		dead_zone = dzr;
	}


	Vec2	last_val = new Vec2();
	long	lasttime = 0;
	/**
	Return a Vec2 representing the direction to go towards the
	goal.  Magnitude varies with distance.
	@param timestamp long, only get new information if timestamp > than last call
                or timestamp == -1.
	@return the movement vector.
	*/
	public Vec2 Value(long timestamp)
	{
		double	mag;
		Vec2 goal = new Vec2();

		if ((timestamp > lasttime)||(timestamp == -1))
		{
			if (DEBUG) System.out.println("v_LinearAttraction_v:");

			/*--- reset the timestamp ---*/
			if (timestamp > 0) lasttime = timestamp;

			/*--- get the goal ---*/
			goal = embedded1.Value(timestamp);

			/*--- consider the magnitude ---*/
			// inside dead zone?
			if (goal.r < dead_zone)
			{
				mag = 0;
			}
			// inside control zone?
			else if (goal.r < controlled_zone)
				mag = (goal.r - dead_zone)/
					(controlled_zone - dead_zone);
			// outside control zone
			else mag = 1.0;
			if (DEBUG) System.out.println(mag+" "+goal.r);
				
			/*--- set the vector ---*/
			goal.setr(mag);
			last_val = goal;
		}
		if (DEBUG) System.out.println(last_val.r+" "+goal.r);
		return (new Vec2(last_val.x, last_val.y));
	}
}