org.apache.commons.math3.geometry.spherical.twod

## Class Circle

• All Implemented Interfaces:
Embedding<Sphere2D,Sphere1D>, Hyperplane<Sphere2D>

public class Circle
extends Object
implements Hyperplane<Sphere2D>, Embedding<Sphere2D,Sphere1D>
This class represents an oriented great circle on the 2-sphere.

An oriented circle can be defined by a center point. The circle is the the set of points that are in the normal plan the center.

Since it is oriented the two spherical caps at its two sides are unambiguously identified as a left cap and a right cap. This can be used to identify the interior and the exterior in a simple way by local properties only when part of a line is used to define part of a spherical polygon boundary.

Since:
3.3
• ### Constructor Summary

Constructors
Constructor and Description
Circle(Circle circle)
Copy constructor.
Circle(S2Point first, S2Point second, double tolerance)
Build a great circle from two non-aligned points.
Circle(Vector3D pole, double tolerance)
Build a great circle from its pole.
• ### Method Summary

Methods
Modifier and Type Method and Description
Circle copySelf()
Copy the instance.
Arc getInsideArc(Circle other)
Get the arc of the instance that lies inside the other circle.
double getOffset(Point<Sphere2D> point)
Get the offset (oriented distance) of a point.
double getOffset(Vector3D direction)
Get the offset (oriented distance) of a direction.
double getPhase(Vector3D direction)
Get the phase angle of a direction.
Vector3D getPointAt(double alpha)
Get a circle point from its phase around the circle.
Vector3D getPole()
Get the pole of the circle.
Circle getReverse()
Get the reverse of the instance.
double getTolerance()
Get the tolerance below which points are considered to belong to the hyperplane.
static Transform<Sphere2D,Sphere1D> getTransform(Rotation rotation)
Get a Transform embedding a 3D rotation.
Vector3D getXAxis()
Get the X axis of the circle.
Vector3D getYAxis()
Get the Y axis of the circle.
Point<Sphere2D> project(Point<Sphere2D> point)
Project a point to the hyperplane.
void reset(Vector3D newPole)
Reset the instance as if built from a pole.
void revertSelf()
Revert the instance.
boolean sameOrientationAs(Hyperplane<Sphere2D> other)
Check if the instance has the same orientation as another hyperplane.
S2Point toSpace(Point<Sphere1D> point)
Transform a sub-space point into a space point.
S1Point toSubSpace(Point<Sphere2D> point)
Transform a space point into a sub-space point.
SubCircle wholeHyperplane()
Build a sub-hyperplane covering the whole hyperplane.
SphericalPolygonsSet wholeSpace()
Build a region covering the whole space.
• ### Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
• ### Constructor Detail

• #### Circle

public Circle(Vector3D pole,
double tolerance)
Build a great circle from its pole.

The circle is oriented in the trigonometric direction around pole.

Parameters:
pole - circle pole
tolerance - tolerance below which close sub-arcs are merged together
• #### Circle

public Circle(S2Point first,
S2Point second,
double tolerance)
Build a great circle from two non-aligned points.

The circle is oriented from first to second point using the path smaller than $$\pi$$.

Parameters:
first - first point contained in the great circle
second - second point contained in the great circle
tolerance - tolerance below which close sub-arcs are merged together
• #### Circle

public Circle(Circle circle)
Copy constructor.

The created instance is completely independent from the original instance, it is a deep copy.

Parameters:
circle - circle to copy
• ### Method Detail

• #### copySelf

public Circle copySelf()
Copy the instance.

The instance created is completely independant of the original one. A deep copy is used, none of the underlying objects are shared (except for immutable objects).

Specified by:
copySelf in interface Hyperplane<Sphere2D>
Returns:
a new hyperplane, copy of the instance
• #### reset

public void reset(Vector3D newPole)
Reset the instance as if built from a pole.

The circle is oriented in the trigonometric direction around pole.

Parameters:
newPole - circle pole
• #### revertSelf

public void revertSelf()
Revert the instance.
• #### getReverse

public Circle getReverse()
Get the reverse of the instance.

Get a circle with reversed orientation with respect to the instance. A new object is built, the instance is untouched.

Returns:
a new circle, with orientation opposite to the instance orientation
• #### project

public Point<Sphere2D> project(Point<Sphere2D> point)
Project a point to the hyperplane.
Specified by:
project in interface Hyperplane<Sphere2D>
Parameters:
point - point to project
Returns:
projected point
• #### getTolerance

public double getTolerance()
Get the tolerance below which points are considered to belong to the hyperplane.
Specified by:
getTolerance in interface Hyperplane<Sphere2D>
Returns:
tolerance below which points are considered to belong to the hyperplane
• #### toSubSpace

public S1Point toSubSpace(Point<Sphere2D> point)
Transform a space point into a sub-space point.
Specified by:
toSubSpace in interface Embedding<Sphere2D,Sphere1D>
Parameters:
point - n-dimension point of the space
Returns:
(n-1)-dimension point of the sub-space corresponding to the specified space point
getPhase(Vector3D)
• #### getPhase

public double getPhase(Vector3D direction)
Get the phase angle of a direction.

The direction may not belong to the circle as the phase is computed for the meridian plane between the circle pole and the direction.

Parameters:
direction - direction for which phase is requested
Returns:
phase angle of the direction around the circle
toSubSpace(Point)
• #### toSpace

public S2Point toSpace(Point<Sphere1D> point)
Transform a sub-space point into a space point.
Specified by:
toSpace in interface Embedding<Sphere2D,Sphere1D>
Parameters:
point - (n-1)-dimension point of the sub-space
Returns:
n-dimension point of the space corresponding to the specified sub-space point
getPointAt(double)
• #### getPole

public Vector3D getPole()
Get the pole of the circle.

As the circle is a great circle, the pole does not belong to it.

Returns:
pole of the circle
getXAxis(), getYAxis()
• #### getInsideArc

public Arc getInsideArc(Circle other)
Get the arc of the instance that lies inside the other circle.
Parameters:
other - other circle
Returns:
arc of the instance that lies inside the other circle
• #### wholeHyperplane

public SubCircle wholeHyperplane()
Build a sub-hyperplane covering the whole hyperplane.
Specified by:
wholeHyperplane in interface Hyperplane<Sphere2D>
Returns:
a sub-hyperplane covering the whole hyperplane
• #### wholeSpace

public SphericalPolygonsSet wholeSpace()
Build a region covering the whole space.
Specified by:
wholeSpace in interface Hyperplane<Sphere2D>
Returns:
a region containing the instance (really a SphericalPolygonsSet instance)
• #### getOffset

public double getOffset(Point<Sphere2D> point)
Get the offset (oriented distance) of a point.

The offset is 0 if the point is on the underlying hyperplane, it is positive if the point is on one particular side of the hyperplane, and it is negative if the point is on the other side, according to the hyperplane natural orientation.

Specified by:
getOffset in interface Hyperplane<Sphere2D>
Parameters:
point - point to check
Returns:
offset of the point
getOffset(Vector3D)
• #### getOffset

public double getOffset(Vector3D direction)
Get the offset (oriented distance) of a direction.

The offset is defined as the angular distance between the circle center and the direction minus the circle radius. It is therefore 0 on the circle, positive for directions outside of the cone delimited by the circle, and negative inside the cone.

Parameters:
direction - direction to check
Returns:
offset of the direction
getOffset(Point)
• #### sameOrientationAs

public boolean sameOrientationAs(Hyperplane<Sphere2D> other)
Check if the instance has the same orientation as another hyperplane.

This method is expected to be called on parallel hyperplanes. The method should not re-check for parallelism, only for orientation, typically by testing something like the sign of the dot-products of normals.

Specified by:
sameOrientationAs in interface Hyperplane<Sphere2D>
Parameters:
other - other hyperplane to check against the instance
Returns:
true if the instance and the other hyperplane have the same orientation