/*
GeoGebra - Dynamic Mathematics for Everyone
http://www.geogebra.org
This file is part of GeoGebra.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation.
*/
/*
* AlgoDirectrix.java
*
* Created on 30. August 2001, 21:37
*/
package org.geogebra.common.kernel.advanced;
import org.geogebra.common.kernel.Construction;
import org.geogebra.common.kernel.StringTemplate;
import org.geogebra.common.kernel.algos.AlgoElement;
import org.geogebra.common.kernel.commands.Commands;
import org.geogebra.common.kernel.geos.GeoConic;
import org.geogebra.common.kernel.geos.GeoElement;
import org.geogebra.common.kernel.geos.GeoLine;
import org.geogebra.common.kernel.geos.GeoPoint;
import org.geogebra.common.kernel.geos.GeoVec2D;
import org.geogebra.common.kernel.kernelND.GeoConicNDConstants;
/**
*
* @author Markus
*/
public class AlgoDirectrix extends AlgoElement {
private GeoConic c; // input
private GeoLine directrix, directrix2; // output
private GeoVec2D[] eigenvec;
private GeoVec2D b;
private GeoPoint P, P2;
public AlgoDirectrix(Construction cons, String label, GeoConic c) {
super(cons);
this.c = c;
eigenvec = c.eigenvec;
b = c.b;
directrix = new GeoLine(cons);
directrix2 = new GeoLine(cons);
P = new GeoPoint(cons);
P2 = new GeoPoint(cons);
directrix.setStartPoint(P);
directrix2.setStartPoint(P2);
setInputOutput(); // for AlgoElement
compute();
directrix2.setLabel(label);
directrix.setLabel(label);
}
@Override
public Commands getClassName() {
return Commands.Directrix;
}
// for AlgoElement
@Override
protected void setInputOutput() {
input = new GeoElement[1];
input[0] = c;
super.setOutputLength(2);
super.setOutput(0, directrix);
super.setOutput(1, directrix2);
setDependencies(); // done by AlgoElement
}
public GeoLine getDirectrix() {
return directrix;
}
public GeoLine getDirectrix2() {
return directrix2;
}
GeoConic getConic() {
return c;
}
// calc axes
@Override
public final void compute() {
// only parabola has directrix
if (c.type == GeoConicNDConstants.CONIC_PARABOLA) {
// directrix has direction of second eigenvector
// through point (b - p/2* eigenvec1)
directrix.x = -eigenvec[1].getY();
directrix.y = eigenvec[1].getX();
double px = b.getX() - c.p / 2.0 * eigenvec[0].getX();
double py = b.getY() - c.p / 2.0 * eigenvec[0].getY();
directrix.z = -(directrix.x * px + directrix.y * py);
directrix2.setUndefined();
} else if (c.type == GeoConicNDConstants.CONIC_ELLIPSE
|| c.type == GeoConicNDConstants.CONIC_HYPERBOLA) {
// https://jira.geogebra.org/browse/GGB-183
// parallel to the minor axis, at a distance a/e away from the
// origin.
double e = c.eccentricity;
double a = c.getHalfAxis(0);
double py = b.getY() + eigenvec[0].getY() * a / e;
double px = b.getX() + eigenvec[0].getX() * a / e;
double py2 = b.getY() - eigenvec[0].getY() * a / e;
double px2 = b.getX() - eigenvec[0].getX() * a / e;
directrix.x = -eigenvec[1].getY();
directrix.y = eigenvec[1].getX();
directrix.z = -(directrix.x * px + directrix.y * py);
P.setCoords(px, py, 1.0);
directrix2.x = -eigenvec[1].getY();
directrix2.y = eigenvec[1].getX();
directrix2.z = -(directrix.x * px2 + directrix.y * py2);
P2.setCoords(px2, py2, 1.0);
} else {
directrix.setUndefined();
directrix2.setUndefined();
}
}
@Override
final public String toString(StringTemplate tpl) {
// Michael Borcherds 2008-03-30
// simplified to allow better Chinese translation
return getLoc().getPlain("DirectrixOfA", c.getLabel(tpl));
}
}