Class v Noise

Класс v_Noise_

/**
 * Генерирует вектор случайным образом на определенное время
 * Generates a vector in a random direction for a specified time.
 * (c)1997 Georgia Tech Research Corporation
 * @author Tucker Balch
 */

package EDU.gatech.cc.is.clay;

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


public class v_Noise_ extends NodeVec2
{
	/**
	 * Turns debug printing on or off.
	 */
	public static final boolean DEBUG = Node.DEBUG;
	private double TIMEOUT = 5.0;
	private	double accum = Math.random()*TIMEOUT;
	private Random r = new Random(0); // constant seed

	/**
	 * Instantiate an v_Noise_ schema.
	 *
	 * @param t double, how long the random direction 
	 *	should persist in seconds.
	 */
	public v_Noise_(double t)
	{
		if (DEBUG) System.out.println("v_Noise_: instantiated.");
		last_val.sett(Math.random()*2*Math.PI);
		TIMEOUT = t;
		r.setSeed(System.currentTimeMillis());
	}


	/**
	 * Instantiate an v_Noise_ schema.
	 *
	 * @param t double, how long the random direction 
	 *	should persist in seconds.
	 * @param s long, the random number seed.
	 */
	public v_Noise_(double t, long s)
	{
		if (DEBUG) System.out.println("v_Noise_: instantiated.");
		last_val.sett(Math.random()*2*Math.PI);
		TIMEOUT = t;
		r.setSeed(s);
	}


	Vec2	last_val = new Vec2();
	long	lasttime = 0;
	/**
	Return a Vec2 representing a random direction to go
	for a period of time.
	@param timestamp only get new information if timestamp > than last call
                or timestamp == -1.
	@return the movement vector.
	*/
	public Vec2 Value(long timestamp)
	{
		double	tempmag;

		if ((timestamp > lasttime)||(timestamp == -1))
		{
			/*--- reset the timestamp ---*/
			double time_incd = (double)(timestamp-lasttime)/1000;
			if (timestamp > 0) lasttime = timestamp;
			else
				timestamp = lasttime + 1;
			accum += time_incd;

			/*--- reset output ---*/
			if (accum > TIMEOUT)
			{
				accum = 0;
				last_val.sett(r.nextDouble()*2*Math.PI);
			}
		}
		return (new Vec2(last_val.x, last_val.y));
	}
}