org.apache.commons.geometry.euclidean.twod.shape

Class Circle

java.lang.Object

org.apache.commons.geometry.euclidean.AbstractNSphere<Vector2D>

org.apache.commons.geometry.euclidean.twod.shape.Circle

All Implemented Interfaces:

Region<Vector2D>, Sized, Linecastable2D

public final class Circle
extends AbstractNSphere<Vector2D>
implements Linecastable2D

Class representing a circle in 2 dimensional Euclidean space.

Method Summary

Modifier and Type	Method and Description
Vector2D	firstIntersection(Line line) Get the first intersection point between the given line and this circle, or null if no such point exists.
static Circle	from(Vector2D center, double radius, Precision.DoubleEquivalence precision) Construct a circle from a center point and radius.
double	getBoundarySize()
double	getSize()
List<Vector2D>	intersections(Line line) Get the intersections of the given line with this circle.
List<LinecastPoint2D>	linecast(LineConvexSubset segment) Intersect the given line subset against the boundaries in this instance, returning a list of all intersections in order of increasing position along the line.
LinecastPoint2D	linecastFirst(LineConvexSubset segment) Intersect the given line subset against the boundaries in this instance, returning the first intersection found when traveling in the direction of the line subset from its start location.
Vector2D	project(Vector2D pt)
RegionBSPTree2D	toTree(int segments) Return a RegionBSPTree2D representing an approximation of the circle.

Methods inherited from class org.apache.commons.geometry.euclidean.AbstractNSphere

classify, equals, firstIntersection, getCenter, getCentroid, getPrecision, getRadius, hashCode, intersections, isEmpty, isFull, project, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.commons.geometry.euclidean.twod.Linecastable2D

linecast, linecastFirst

Methods inherited from interface org.apache.commons.geometry.core.Region

contains

Methods inherited from interface org.apache.commons.geometry.core.Sized

isFinite, isInfinite

Method Detail

getSize

public double getSize()

Specified by:

getSize in interface Sized

getBoundarySize

public double getBoundarySize()

Specified by:

getBoundarySize in interface Region<Vector2D>

project

public Vector2D project(Vector2D pt)

Specified by:

project in interface Region<Vector2D>

toTree

public RegionBSPTree2D toTree(int segments)

Return a RegionBSPTree2D representing an approximation of the circle. All points in the approximation are contained in the circle (ie, they lie inside or on the boundary). No guarantees are made regarding the internal structure of the returned tree. Non-boundary split nodes may be used in order to balance the tree and improve performance.

Choosing an appropriate number of segments for an approximation is a trade-off between size and accuracy: approximations with large numbers of segments more closely match the geometric properties of the circle but at the cost of using larger tree structures. In general, the smallest number of segments that produces an acceptable result should be used.

Parameters:

segments - number of line segments to use for the boundary of the circle approximation

Returns:

a BSP tree approximation of the circle

Throws:

IllegalArgumentException - if segments is less than 3

intersections

public List<Vector2D> intersections(Line line)

Get the intersections of the given line with this circle. The returned list will contain either 0, 1, or 2 points.

• 2 points - The line is a secant line and intersects the circle at two distinct points. The points are ordered such that the first point in the list is the first point encountered when traveling in the direction of the line. (In other words, the points are ordered by increasing abscissa value.)
• 1 point - The line is a tangent line and only intersects the circle at a single point (as evaluated by the circle's precision context).
• 0 points - The line does not intersect the circle.

Parameters:

line - line to intersect with the circle

Returns:

a list of intersection points between the given line and this circle

firstIntersection

public Vector2D firstIntersection(Line line)

Get the first intersection point between the given line and this circle, or null if no such point exists. The "first" intersection point is the first such point encountered when traveling in the direction of the line from infinity.

Parameters:

line - line to intersect with the circle

Returns:

the first intersection point between the given line and this instance or null if no such point exists

linecast

public List<LinecastPoint2D> linecast(LineConvexSubset segment)

Intersect the given line subset against the boundaries in this instance, returning a list of all intersections in order of increasing position along the line. An empty list is returned if no intersections are discovered.

Specified by:

linecast in interface Linecastable2D

Parameters:

segment - line subset to intersect

Returns:

a list of computed intersections in order of increasing position along the line

linecastFirst

public LinecastPoint2D linecastFirst(LineConvexSubset segment)

Intersect the given line subset against the boundaries in this instance, returning the first intersection found when traveling in the direction of the line subset from its start location.

Specified by:

linecastFirst in interface Linecastable2D

Parameters:

segment - line subset to intersect

Returns:

the first intersection found or null if no intersection is found

from

public static Circle from(Vector2D center,
                          double radius,
                          Precision.DoubleEquivalence precision)

Construct a circle from a center point and radius.

Parameters:

center - the center point of the circle

radius - the circle radius

precision - precision precision context used to compare floating point numbers

Returns:

a circle with the given center and radius

Throws:

IllegalArgumentException - if center is not finite or radius is not finite or is less than or equal to zero as evaluated by the given precision context