/*
RepRap
------
The Replicating Rapid Prototyper Project
Copyright (C) 2005
Adrian Bowyer & The University of Bath
http://reprap.org
Principal author:
Adrian Bowyer
Department of Mechanical Engineering
Faculty of Engineering and Design
University of Bath
Bath BA2 7AY
U.K.
e-mail: A.Bowyer@bath.ac.uk
RepRap is free; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
Licence as published by the Free Software Foundation; either
version 2 of the Licence, or (at your option) any later version.
RepRap 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
Library General Public Licence for more details.
For this purpose the words "software" and "library" in the GNU Library
General Public Licence are taken to mean any and all computer programs
computer files data results documents and other copyright information
available from the RepRap project.
You should have received a copy of the GNU Library General Public
Licence along with RepRap; if not, write to the Free
Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA,
or see
http://www.gnu.org/
=====================================================================
Rr2Point: 2D vectors
First version 20 May 2005
This version: 1 May 2006 (Now in CVS - no more comments here)
*/
package org.reprap.geometry.polygons;
/**
* Class for (x, y) points and vectors
*/
public class Point2D
{
/**
*
*/
private double x, y;
/**
* Destroy me and all I point to
*/
public void destroy()
{
// I don't point to anything
}
/**
* Destroy just me
*/
// protected void finalize() throws Throwable
// {
// super.finalize();
// }
/**
* Default to the origin
*/
public Point2D()
{
x = 0;
y = 0;
}
/**
* Usual constructor
* @param a
* @param b
*/
public Point2D(double a, double b)
{
x = a;
y = b;
}
/**
* Copy
* @param r Rr2Point to copy from
*/
public Point2D(Point2D r)
{
x = r.x;
y = r.y;
}
/* (non-Javadoc)
* @see java.lang.Object#toString()
*/
public String toString()
{
return Double.toString(x) + " " + Double.toString(y);
}
/**
* Coordinates
*/
public double x() { return x; }
public double y() { return y; }
/**
* Arithmetic
* @return neg of point
*/
public Point2D neg()
{
return new Point2D(-x, -y);
}
/**
* @return orthogonal of (this) point
*/
public Point2D orthogonal()
{
return new Point2D(y, -x);
}
/**
* @param a
* @param b
* @return a new point based on a vector addition of points a and b
*/
public static Point2D add(Point2D a, Point2D b)
{
Point2D r = new Point2D(a);
r.x += b.x;
r.y += b.y;
return r;
}
/**
* @param a
* @param b
* @return a new point based on a vector subtraction of a - b
*/
public static Point2D sub(Point2D a, Point2D b)
{
return add(a, b.neg());
}
/**
* Scale a point
* @param b An R2rPoint
* @param factor A scale factor
* @return The point Rr2Point scaled by a factor of factor
*/
public static Point2D mul(Point2D b, double factor)
{
return new Point2D(b.x*factor, b.y*factor);
}
/**
* @param a
* @param b
* @return the point Rr2Point scaled by a factor of a
*/
public static Point2D mul(double a, Point2D b)
{
return mul(b, a);
}
/**
* Downscale a point
* @param b An R2rPoint
* @param factor A scale factor
* @return The point Rr2Point divided by a factor of a
*/
public static Point2D div(Point2D b, double factor)
{
return mul(b, 1/factor);
}
/**
* Inner product
* @param a
* @param b
* @return The scalar product of the points
*/
public static double mul(Point2D a, Point2D b)
{
return a.x*b.x + a.y*b.y;
}
/**
* Modulus
* @return modulus
*/
public double mod()
{
return Math.sqrt(mul(this, this));
}
/**
* Unit length normalization
* @return normalized unit lenght
*/
public Point2D norm()
{
return div(this, mod());
}
/**
* Outer product
* @param a
* @param b
* @return oute product
*/
public static double op(Point2D a, Point2D b)
{
return a.x*b.y - a.y*b.x;
}
/**
* Gradient
* @return gradient
*/
public double gradient()
{
double g;
if(x == 0)
{
if(y > 0)
g = Double.POSITIVE_INFINITY;
else
g = Double.NEGATIVE_INFINITY;
} else
g = y/x;
return g;
}
/**
* Squared distance
* @param a
* @param b
* @return squared distance
*/
public static double dSquared(Point2D a, Point2D b)
{
Point2D c = sub(a, b);
return mul(c, c);
}
/**
* distance
* @param a
* @param b
* @return distance
*/
public static double d(Point2D a, Point2D b)
{
return Math.sqrt(dSquared(a, b));
}
/**
* The same, withing tolerance?
* @param a
* @param b
* @param tol_2
* @return true if the squared distance between points a and b
* is within tolerance tol_2, otherwise false
*/
public static boolean same(Point2D a, Point2D b, double tol_2)
{
return dSquared(a, b) < tol_2;
}
}