rescuecore2.misc.geometry

Class GeometryTools2D

java.lang.Object

rescuecore2.misc.geometry.GeometryTools2D

public final class GeometryTools2D
extends java.lang.Object

A bunch of useful 2D geometry tools: finding line intersections, closest points and so on.

Field Summary

Fields

Modifier and Type	Field and Description
static double	THRESHOLD The threshold for equality testing in geometric operations.

Method Summary

Modifier and Type	Method and Description
static Line2D	clipToRectangle(Line2D line, double xMin, double yMin, double xMax, double yMax) Clip a line to a rectangle.
static double	computeArea(java.util.List<Point2D> vertices) Compute the area of a simple polygon.
static Point2D	computeCentroid(java.util.List<Point2D> vertices) Compute the centroid of a simple polygon.
static boolean	contains(Line2D line, Point2D point) Find out if a point is on a line.
static double	getAngleBetweenVectors(Vector2D first, Vector2D second) Compute the angle between two vectors in degrees.
static Point2D	getClosestPoint(Line2D line, Point2D point) Find the closest point on a line.
static Point2D	getClosestPointOnSegment(Line2D line, Point2D point) Find the closest point on a line.
static double	getDistance(Point2D p1, Point2D p2) Compute the distance between two points.
static Point2D	getIntersectionPoint(Line2D l1, Line2D l2) Find the intersection point of two lines.
static double	getLeftAngleBetweenLines(Line2D first, Line2D second) Compute the angle between two lines in a counter-clockwise direction.
static double	getLeftAngleBetweenVectors(Vector2D first, Vector2D second) Compute the angle between two vectors in a counter-clockwise direction.
static double	getRightAngleBetweenLines(Line2D first, Line2D second) Compute the angle between two lines in a clockwise direction.
static double	getRightAngleBetweenVectors(Vector2D first, Vector2D second) Compute the angle between two vectors in a clockwise direction.
static Point2D	getSegmentIntersectionPoint(Line2D l1, Line2D l2) Find the intersection point of two line segments.
static boolean	isRightTurn(Line2D first, Line2D second) Find out if we turn right from one line to another.
static boolean	isRightTurn(Vector2D first, Vector2D second) Find out if we turn right from one vector to another.
static boolean	nearlyZero(double d) Find out if a number is near enough to zero.
static boolean	parallel(Line2D l1, Line2D l2) Are two lines parallel?
static java.util.List<Line2D>	pointsToLines(java.util.List<Point2D> points) Convert a list of Point2D objects to a list of lines connecting adjacent points.
static java.util.List<Line2D>	pointsToLines(java.util.List<Point2D> points, boolean close) Convert a list of Point2D objects to a list of lines connecting adjacent points.
static double	positionOnLine(Line2D line, Point2D point) Find out how far a point is along a line.
static java.util.List<Point2D>	vertexArrayToPoints(double[] vertices) Convert a vertex array to a list of Point2D objects.
static java.util.List<Point2D>	vertexArrayToPoints(int[] vertices) Convert a vertex array to a list of Point2D objects.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

THRESHOLD

public static final double THRESHOLD

The threshold for equality testing in geometric operations. Lines will be considered parallel if the D factor is less than this; points will be considered equivalent if their position difference is less than this and so on.

See Also:

Constant Field Values

Method Detail

getIntersectionPoint

public static Point2D getIntersectionPoint(Line2D l1,
                                           Line2D l2)

Find the intersection point of two lines.

Parameters:

l1 - The first line.

l2 - The second line.

Returns:

The intersection point of the two lines, or null if the lines are parallel.

getSegmentIntersectionPoint

public static Point2D getSegmentIntersectionPoint(Line2D l1,
                                                  Line2D l2)

Find the intersection point of two line segments.

Parameters:

l1 - The first line segment.

l2 - The second line segment.

Returns:

The intersection point, or null if the line segments are parallel or do not intersect.

parallel

public static boolean parallel(Line2D l1,
                               Line2D l2)

Are two lines parallel?

Parameters:

l1 - The first line.

l2 - The second line.

Returns:

true iff the lines are parallel (within tolerance). Direction does not matter; lines pointing in opposite directions are still parallel.

contains

public static boolean contains(Line2D line,
                               Point2D point)

Find out if a point is on a line.

Parameters:

line - The line to test.

point - The point to test.

Returns:

true iff the point is on the line (within tolerance).

positionOnLine

public static double positionOnLine(Line2D line,
                                    Point2D point)

Find out how far a point is along a line.

Parameters:

line - The line to test.

point - The point to test.

Returns:

The t value of the point along the line, or NaN if the point is not on the line.

getRightAngleBetweenLines

public static double getRightAngleBetweenLines(Line2D first,
                                               Line2D second)

Compute the angle between two lines in a clockwise direction.

Parameters:

first - The first line.

second - The second line.

Returns:

The angle in degrees measured in a clockwise direction.

getLeftAngleBetweenLines

public static double getLeftAngleBetweenLines(Line2D first,
                                              Line2D second)

Compute the angle between two lines in a counter-clockwise direction.

Parameters:

first - The first line.

second - The second line.

Returns:

The angle in degrees measured in a counter-clockwise direction.

getAngleBetweenVectors

public static double getAngleBetweenVectors(Vector2D first,
                                            Vector2D second)

Compute the angle between two vectors in degrees.

Parameters:

first - The first vector.

second - The second vector.

Returns:

The angle in degrees. This will be between 0 and 180.

getRightAngleBetweenVectors

public static double getRightAngleBetweenVectors(Vector2D first,
                                                 Vector2D second)

Compute the angle between two vectors in a clockwise direction.

Parameters:

first - The first vector.

second - The second vector.

Returns:

The angle in degrees measured in a clockwise direction.

getLeftAngleBetweenVectors

public static double getLeftAngleBetweenVectors(Vector2D first,
                                                Vector2D second)

Compute the angle between two vectors in a counter-clockwise direction.

Parameters:

first - The first vector.

second - The second vector.

Returns:

The angle in degrees measured in a counter-clockwise direction.

isRightTurn

public static boolean isRightTurn(Line2D first,
                                  Line2D second)

Find out if we turn right from one line to another.

Parameters:

first - The first line.

second - The second line.

Returns:

True if the second line is a right turn from the first, false otherwise.

isRightTurn

public static boolean isRightTurn(Vector2D first,
                                  Vector2D second)

Find out if we turn right from one vector to another.

Parameters:

first - The first vector.

second - The second vector.

Returns:

True if the second vector is a right turn from the first, false otherwise.

nearlyZero

public static boolean nearlyZero(double d)

Find out if a number is near enough to zero.

Parameters:

d - The number to test.

Returns:

true iff the number is nearly zero.

computeArea

public static double computeArea(java.util.List<Point2D> vertices)

Compute the area of a simple polygon.

Parameters:

vertices - The vertices of the polygon.

Returns:

The area of the polygon.

computeCentroid

public static Point2D computeCentroid(java.util.List<Point2D> vertices)

Compute the centroid of a simple polygon.

Parameters:

vertices - The vertices of the polygon.

Returns:

The centroid.

vertexArrayToPoints

public static java.util.List<Point2D> vertexArrayToPoints(int[] vertices)

Convert a vertex array to a list of Point2D objects.

Parameters:

vertices - The vertices in x, y order.

Returns:

A list of Point2D objects.

vertexArrayToPoints

public static java.util.List<Point2D> vertexArrayToPoints(double[] vertices)

Convert a vertex array to a list of Point2D objects.

Parameters:

vertices - The vertices in x, y order.

Returns:

A list of Point2D objects.

pointsToLines

public static java.util.List<Line2D> pointsToLines(java.util.List<Point2D> points)

Convert a list of Point2D objects to a list of lines connecting adjacent points. The shape will not be automatically closed.

Parameters:

points - The points to connect.

Returns:

A list of Line2D objects.

pointsToLines

public static java.util.List<Line2D> pointsToLines(java.util.List<Point2D> points,
                                                   boolean close)

Convert a list of Point2D objects to a list of lines connecting adjacent points.

Parameters:

points - The points to connect.

close - Whether to close the shape or not.

Returns:

A list of Line2D objects.

getClosestPoint

public static Point2D getClosestPoint(Line2D line,
                                      Point2D point)

Find the closest point on a line.

Parameters:

line - The line to check.

point - The point to check against.

Returns:

The point on the line that is closest to the reference point.

getClosestPointOnSegment

public static Point2D getClosestPointOnSegment(Line2D line,
                                               Point2D point)

Find the closest point on a line.

Parameters:

line - The line to check.

point - The point to check against.

Returns:

The point on the line that is closest to the reference point.

getDistance

public static double getDistance(Point2D p1,
                                 Point2D p2)

Compute the distance between two points.

Parameters:

p1 - The first point.

p2 - The second point.

Returns:

The distance between the two points.

clipToRectangle

public static Line2D clipToRectangle(Line2D line,
                                     double xMin,
                                     double yMin,
                                     double xMax,
                                     double yMax)

Clip a line to a rectangle.

Parameters:

line - The line to clip.

xMin - The lower X coordinate of the rectangle.

yMin - The lower Y coordinate of the rectangle.

xMax - The upper X coordinate of the rectangle.

yMax - The upper Y coordinate of the rectangle.

Returns:

A clipped line, or null if the line is outside the rectangle.