Package com.google.common.geometry

Class S2Loop.CompareBoundaryRelation

java.lang.Object

com.google.common.geometry.S2Loop.CompareBoundaryRelation

All Implemented Interfaces:

S2Loop.LoopRelation

Enclosing class:

S2Loop

private static final class S2Loop.CompareBoundaryRelation
extends Object
implements S2Loop.LoopRelation

Loop relation for compareBoundary().

Field Summary

Fields

Modifier and Type	Field	Description
private final boolean	bReversed	True if loop B should be reversed.
private boolean	containsEdge	True if any edge of B is contained by A.
private boolean	excludesEdge	True if any edge of B is excluded by A.
private boolean	foundSharedVertex	True if any wedge was processed.

Constructor Summary

Constructors

Constructor	Description
CompareBoundaryRelation(boolean reverseB)

Method Summary

Modifier and Type	Method	Description
int	aCrossingTarget()	The CompareBoundaryRelation does not have a useful early-exit condition, so we return -1 for both crossing targets.
int	bCrossingTarget()
boolean	containsEdge()
boolean	foundSharedVertex()
boolean	wedgesCross(S2Point a0, S2Point ab1, S2Point a2, S2Point b0, S2Point b2)	Given a vertex ab1 that is shared between the two loops, returns true if the two associated wedges (a0, ab1, b2) and (b0, ab1, b2) are equivalent to an edge crossing.

Methods inherited from class java.lang.Object

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

Field Details

bReversed

private final boolean bReversed

True if loop B should be reversed.

foundSharedVertex

private boolean foundSharedVertex

True if any wedge was processed.

containsEdge

private boolean containsEdge

True if any edge of B is contained by A.

excludesEdge

private boolean excludesEdge

True if any edge of B is excluded by A.

Constructor Details

CompareBoundaryRelation

public CompareBoundaryRelation(boolean reverseB)

Method Details

foundSharedVertex

public boolean foundSharedVertex()

containsEdge

public boolean containsEdge()

aCrossingTarget

public int aCrossingTarget()

The CompareBoundaryRelation does not have a useful early-exit condition, so we return -1 for both crossing targets.

Aside: A possible early exit condition could be based on the following:

• If A contains a point of both B and ~B, then A intersects Boundary(B).
• If ~A contains a point of both B and ~B, then ~A intersects Boundary(B).
• So if the intersections of {A, ~A} with {B, ~B} are all non-empty, the return value is 0, i.e., Boundary(A) intersects Boundary(B).

Unfortunately, it isn't worth detecting this situation because by the time we have seen a point in all four intersection regions, we are also guaranteed to have seen at least one pair of crossing edges.

Specified by:

aCrossingTarget in interface S2Loop.LoopRelation

bCrossingTarget

public int bCrossingTarget()

Specified by:

bCrossingTarget in interface S2Loop.LoopRelation

wedgesCross

public boolean wedgesCross(S2Point a0,
 S2Point ab1,
 S2Point a2,
 S2Point b0,
 S2Point b2)

Description copied from interface: S2Loop.LoopRelation

Given a vertex ab1 that is shared between the two loops, returns true if the two associated wedges (a0, ab1, b2) and (b0, ab1, b2) are equivalent to an edge crossing. The loop relation is also allowed to maintain its own internal state, and can return true if it observes any sequence of wedges that are equivalent to an edge crossing.

Specified by:

wedgesCross in interface S2Loop.LoopRelation