VisibilityCalculatorImpl.java

/*******************************************************************************
 * Copyright 2012 Geoscience Australia
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/
package au.gov.ga.earthsci.worldwind.common.layers.geonames;

import gov.nasa.worldwind.geom.LatLon;
import gov.nasa.worldwind.geom.Position;
import gov.nasa.worldwind.geom.Sector;

/**
 * Implementation of the {@link VisibilityCalculator} interface.
 * 
 * @author Michael de Hoog (michael.dehoog@ga.gov.au)
 */
public class VisibilityCalculatorImpl implements VisibilityCalculator
{
	private Sector sector = Sector.FULL_SPHERE;
	private int levels = 0;
	private Position eye = Position.ZERO;
	private Object lock = new Object();

	private Sector[] levelSectors;
	private boolean dirty = true;

	public VisibilityCalculatorImpl()
	{
	}

	@Override
	public boolean isVisible(GeoName geoname)
	{
		synchronized (lock)
		{
			if (dirty || levelSectors.length < levels)
			{
				calculateLevelSectors();
			}

			if (geoname.level >= levels)
				return false;

			if (geoname.level <= 1) //levels 0 and 1 are always visible
				return true;
			if (levelSectors[geoname.level].contains(geoname.latlon))
				return true;
			if (sector == null)
				return true;

			return sector.contains(geoname.latlon);
		}
	}

	private void calculateLevelSectors()
	{
		levelSectors = new Sector[levels];
		double width = 360 / 2;
		double height = 180 / 2;
		for (int i = 0; i < levels; i++)
		{
			width /= 2d;
			height /= 2d;
			double lat = eye.getLatitude().degrees; //-90 to 90
			double lon = eye.getLongitude().degrees; //-180 to 180
			levelSectors[i] = Sector.fromDegrees(lat - height, lat + height, lon - width, lon + width);
		}

		dirty = false;
	}

	public Sector getSector()
	{
		return sector;
	}

	public void setSector(Sector sector)
	{
		synchronized (lock)
		{
			this.sector = sector;
		}
	}

	public int getLevels()
	{
		return levels;
	}

	public void setLevels(int levels)
	{
		synchronized (lock)
		{
			this.levels = levels;
			dirty = true;
		}
	}

	public Position getEye()
	{
		return eye;
	}

	public void setEye(Position eye)
	{
		synchronized (lock)
		{
			this.eye = eye;
			dirty = true;
		}
	}

	public double distanceSquaredFromEye(GeoName geoname)
	{
		return latlonDistanceSquared(eye, geoname.latlon);
	}

	public static double latlonDistanceSquared(LatLon ll1, LatLon ll2)
	{
		double latDelta = ll1.getLatitude().degrees - ll2.getLatitude().degrees;
		double lonDelta = ll1.getLongitude().degrees - ll2.getLongitude().degrees;
		return (latDelta * latDelta) + (lonDelta * lonDelta);
	}
}