Polygon2d.java

/*-
 *  Copyright 2020 Beuth Hochschule für Technik Berlin, Hochschule für Technik Stuttgart
 * 
 *  This file is part of CityDoctor2.
 *
 *  CityDoctor2 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, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  CityDoctor2 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.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with CityDoctor2.  If not, see <https://www.gnu.org/licenses/>.
 */
package de.hft.stuttgart.citydoctor2.math;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import de.hft.stuttgart.citydoctor2.datastructure.LinearRing;
import de.hft.stuttgart.citydoctor2.datastructure.Polygon;
import de.hft.stuttgart.citydoctor2.datastructure.Vertex;

/**
 * A two dimensional polygon. Has an 2d exterior ring and interior rings
 * 
 * @author Matthias Betz
 *
 */
public class Polygon2d {

	private Ring2d exterior;
	private List<Ring2d> innerRings;

	public static Polygon2d withProjection(Polygon poly) {
		Vector3d normal = poly.calculateNormalNormalized();
		int[] axis = getProjectionAxis(normal);
		return projectTo2D(poly, axis);
	}

	public static Polygon2d withProjection(MovedPolygon poly, int[] projectionAxis) {
		return projectTo2D(poly, projectionAxis);
	}

	public static Polygon2d withProjection(Polygon poly, int[] projectionAxis) {
		return projectTo2D(poly, projectionAxis);
	}

	private static Polygon2d projectTo2D(Polygon p, int[] axis) {
		List<Ring2d> interior = new ArrayList<>();
		Ring2d exterior = projectRing(p.getExteriorRing(), axis);
		for (LinearRing innerRing : p.getInnerRings()) {
			interior.add(projectRing(innerRing, axis));
		}
		return new Polygon2d(exterior, interior);
	}

	private static Polygon2d projectTo2D(MovedPolygon p, int[] axis) {
		List<Ring2d> interior = new ArrayList<>();
		Ring2d exterior = projectRing(p.getExteriorRing(), axis);
		for (MovedRing innerRing : p.getInnerRings()) {
			interior.add(projectRing(innerRing, axis));
		}
		return new Polygon2d(exterior, interior);
	}

	public static int[] getProjectionAxis(Vector3d normal) {
		double nx = Math.abs(normal.getX());
		double ny = Math.abs(normal.getY());
		double nz = Math.abs(normal.getZ());
		int[] axis;
		if (nx >= ny && nx >= nz) {
			axis = new int[] { 1, 2 };
		} else if (ny >= nx && ny >= nz) {
			axis = new int[] { 0, 2 };
		} else {
			axis = new int[] { 0, 1 };
		}
		return axis;
	}

	private static Ring2d projectRing(LinearRing r, int[] axis) {
		List<Vector2d> projectedVertices = new ArrayList<>();
		for (Vertex v : r.getVertices()) {
			projectedVertices.add(new Vector2d(v.getCoordinate(axis[0]), v.getCoordinate(axis[1])));
		}
		return new Ring2d(projectedVertices, r);
	}

	private static Ring2d projectRing(MovedRing r, int[] axis) {
		List<Vector2d> projectedVertices = new ArrayList<>();
		for (Vector3d v : r.getVertices()) {
			projectedVertices.add(new Vector2d(v.getCoordinate(axis[0]), v.getCoordinate(axis[1])));
		}
		return new Ring2d(projectedVertices, r.getOriginal());
	}

	public static Polygon2d withRotationMatrix(Polygon poly) {
		Matrix3x3d rotMatrix = PolygonUtils.calculateRotationMatrix(poly);

		LinearRing lr = poly.getExteriorRing();
		Ring2d exterior = createRing2d(rotMatrix, lr);

		List<Ring2d> innerRings = new ArrayList<>();
		for (LinearRing innerRing : poly.getInnerRings()) {
			innerRings.add(createRing2d(rotMatrix, innerRing));
		}
		return new Polygon2d(exterior, innerRings);
	}

	/**
	 * Converts a Polygon to a 2d polygon. This will change the area of the polygon.
	 * 
	 * @param ring a linear ring
	 */
	private Polygon2d(Ring2d exterior, List<Ring2d> interior) {
		if (interior == null) {
			interior = Collections.emptyList();
		}
		this.exterior = exterior;
		this.innerRings = interior;
	}

	private static Ring2d createRing2d(Matrix3x3d rotMatrix, LinearRing lr) {
		List<Vector2d> ringVertices = new ArrayList<>();
		for (Vertex v : lr.getVertices()) {
			Vector3d rotated = rotMatrix.mult(v);
			Vector2d v2d = new Vector2d(rotated.getX(), rotated.getY());
			ringVertices.add(v2d);
		}
		return new Ring2d(ringVertices, lr);
	}

	public Ring2d getExterior() {
		return exterior;
	}

	public List<Ring2d> getInteriorRings() {
		if (innerRings == null) {
			return Collections.emptyList();
		}
		return innerRings;
	}

}