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package visualiser.model;
import shared.model.GPSCoordinate;
/**
* A TrackPoint is a point plotted to display the track a
* {@link VisualiserBoat Boat} has travelled in a race. <br>
* TrackPoints are displayed on a
* {@link ResizableRaceCanvas}, via the
* {@link visualiser.Controllers.RaceController}. <br>
* Track points can be made visible or hidden via the RaceController's
* {@link Annotations}.
*/
public class TrackPoint {
/**
* The {@link GPSCoordinate} this {@link TrackPoint} corresponds to.
*/
private final GPSCoordinate coordinate;
/**
* The time the track point was created at, in milliseconds since unix epoch.
*/
private final long timeAdded;
/**
* The period of time, in milliseconds, over which the track point's alpha should diminish to a floor value of {@link #minAlpha}.
*/
private final long expiry;
/**
* The minimum alpha to draw the track point with.
*/
private final double minAlpha;
/**
* The diameter to draw the track point with.
*/
private final double diameter;
/**
* Creates a new track point with fixed GPS coordinates and time, to reach minimum opacity on expiry.
*
* @param coordinate position of point on physical race map
* @param timeAdded system clock at time of addition
* @param expiry time to minimum opacity after added
*/
public TrackPoint(GPSCoordinate coordinate, long timeAdded, long expiry) {
this.coordinate = coordinate;
this.timeAdded = timeAdded;
this.expiry = expiry;
this.minAlpha = 0.1;
this.diameter = 5d;
}
/**
* Gets the position of the point on physical race map.
*
* @return GPS coordinate of point
*/
public GPSCoordinate getCoordinate() {
return coordinate;
}
/**
* Gets opacity of point scaled by age in proportion to expiry, between 1 and minimum opacity inclusive.
*
* @return Greater of minimum opacity and scaled opacity.
*/
public double getAlpha() {
//Calculate how much the alpha should be attenuated by elapsed time.
//Elapsed time.
long elapsedTime = System.currentTimeMillis() - this.timeAdded;
//Proportion of expiry period that has elapsed. (E.g., 2.5 means that 5 times the period has elapsed.)
double elapsedProportion = ((double) elapsedTime) / this.expiry;
//As the alpha diminishes from 1 down to a floor, we take the complement of this value. This may be negative.
double calculatedAlpha = 1.0 - elapsedProportion;
//We then take the max of the minAlpha and calculatedAlpha so that it doesn't go past our floor value.
return Double.max(this.minAlpha, calculatedAlpha);
}
/**
* Gets time point was added to track.
*
* @return system clock at time of addition
*/
public long getTimeAdded() {
return timeAdded;
}
/**
* Returns the diameter to draw the track point with.
* @return The diameter to draw the track point with.
*/
public double getDiameter() {
return diameter;
}
}