/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2010, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.grid.hexagon;
import org.geotools.geometry.jts.ReferencedEnvelope;
import org.geotools.grid.PolygonBuilder;
import org.geotools.grid.PolygonElement;
import org.geotools.grid.Neighbor;
/**
* Used by {@code Hexagons} class to build grids.
*
* @author mbedward
* @since 2.7
*
*
* @source $URL: http://svn.osgeo.org/geotools/trunk/modules/unsupported/grid/src/main/java/org/geotools/grid/hexagon/HexagonBuilder.java $
* @version $Id: Hexagon.java 35637 2010-06-01 09:24:43Z mbedward $
*/
public class HexagonBuilder extends PolygonBuilder {
private final double sideLen;
private final HexagonOrientation orientation;
private final Neighbor[] nextX = new Neighbor[2];
private final Neighbor[] nextY = new Neighbor[2];
private int xIndex = 0;
private int yIndex = 0;
public HexagonBuilder(ReferencedEnvelope gridBounds, double sideLen, HexagonOrientation orientation) {
super(gridBounds);
this.sideLen = sideLen;
this.orientation = orientation;
if (orientation == HexagonOrientation.ANGLED) {
nextX[0] = nextX[1] = Neighbor.RIGHT;
nextY[0] = Neighbor.UPPER_RIGHT;
nextY[1] = Neighbor.UPPER_LEFT;
} else { // FLAT
nextX[0] = Neighbor.LOWER_RIGHT;
nextX[1] = Neighbor.UPPER_RIGHT;
nextY[0] = nextY[1] = Neighbor.UPPER;
}
}
/**
* Tests whether a neighbor position is valid for a given orientation.
* Since the {@code Hexagon} class is intended to work within a grid
* (ie. a perfect tesselation) some combinations of neighbour position
* and hexagon orientation are invalid. For example, a {@code FLAT}
* hexagon does not have a {@code LEFT}, rather it has {@code UPPER_LEFT}
* and {@code LOWER_LEFT}.
*
* @param orientation hexagon orientation
*
* @param neighbor neighbor position
*
* @return {@code true} if the combination is valid; {@code false} otherwise
*/
@Override
public boolean isValidNeighbor(Neighbor neighbor) {
switch (neighbor) {
case LEFT:
case RIGHT:
return orientation == HexagonOrientation.ANGLED;
case LOWER:
case UPPER:
return orientation == HexagonOrientation.FLAT;
case LOWER_LEFT:
case LOWER_RIGHT:
case UPPER_LEFT:
case UPPER_RIGHT:
return true;
default:
throw new IllegalArgumentException("Invalid value for neighbor");
}
}
/**
* Creates a new {@code Hexagon} positioned at the given neighbor position
* relative to the reference element.
*
* @param el the reference hexagon
*
* @param neighbor a valid neighbour position given the reference hexagon's
* orientation
*
* @return a new {@code Hexagon} object
*
* @throws IllegalArgumentException if either argument is {@code null} or
* if {@code el} is not an instance of {@code Hexagon} or
* if the neighbor position is not valid for the reference hexagon's
* orientation
*
* @see #isValidNeighbor(Hexagon.Orientation, Hexagon.Neighbor)
*/
@Override
public Hexagon createNeighbor(PolygonElement el, Neighbor neighbor) {
if (el == null || neighbor == null) {
throw new IllegalArgumentException(
"el and neighbour position must both be non-null");
}
if (!(el instanceof Hexagon)) {
throw new IllegalArgumentException("el must be an instance of Hexagon");
}
Hexagon hexagon = (Hexagon) el;
if (!isValidNeighbor(neighbor)) {
throw new IllegalArgumentException(
neighbor + " is not a valid neighbour position for orientation " +
hexagon.getOrientation());
}
ReferencedEnvelope bounds = hexagon.getBounds();
double dx, dy;
switch (neighbor) {
case LEFT:
dx = -bounds.getWidth();
dy = 0.0;
break;
case LOWER:
dx = 0.0;
dy = -bounds.getHeight();
break;
case LOWER_LEFT:
if (hexagon.getOrientation() == HexagonOrientation.FLAT) {
dx = -0.75 * bounds.getWidth();
dy = -0.5 * bounds.getHeight();
} else { // ANGLED
dx = -0.5 * bounds.getWidth();
dy = -0.75 * bounds.getHeight();
}
break;
case LOWER_RIGHT:
if (hexagon.getOrientation() == HexagonOrientation.FLAT) {
dx = 0.75 * bounds.getWidth();
dy = -0.5 * bounds.getHeight();
} else { // ANGLED
dx = 0.5 * bounds.getWidth();
dy = -0.75 * bounds.getHeight();
}
break;
case RIGHT:
dx = bounds.getWidth();
dy = 0.0;
break;
case UPPER:
dx = 0.0;
dy = bounds.getHeight();
break;
case UPPER_LEFT:
if (hexagon.getOrientation() == HexagonOrientation.FLAT) {
dx = -0.75 * bounds.getWidth();
dy = 0.5 * bounds.getHeight();
} else { // ANGLED
dx = -0.5 * bounds.getWidth();
dy = 0.75 * bounds.getHeight();
}
break;
case UPPER_RIGHT:
if (hexagon.getOrientation() == HexagonOrientation.FLAT) {
dx = 0.75 * bounds.getWidth();
dy = 0.5 * bounds.getHeight();
} else { // ANGLED
dx = 0.5 * bounds.getWidth();
dy = 0.75 * bounds.getHeight();
}
break;
default:
throw new IllegalArgumentException("Unrecognized value for neighbor");
}
return Hexagons.create(bounds.getMinX() + dx, bounds.getMinY() + dy,
hexagon.getSideLength(), hexagon.getOrientation(),
bounds.getCoordinateReferenceSystem());
}
@Override
public PolygonElement getFirstElement() {
return Hexagons.create(
gridBounds.getMinX(), gridBounds.getMinY(),
sideLen, orientation, gridBounds.getCoordinateReferenceSystem());
}
@Override
public PolygonElement getNextXElement(PolygonElement el) {
Hexagon h = createNeighbor(el, nextX[xIndex]);
xIndex = (xIndex + 1) % 2;
return h;
}
@Override
public PolygonElement getNextYElement(PolygonElement el) {
Hexagon h = createNeighbor(el, nextY[yIndex]);
yIndex = (yIndex + 1) % 2;
xIndex = 0;
return h;
}
@Override
public boolean isValidDenseVertexSpacing(double v) {
return v > 0 && v < sideLen / 2.0;
}
}