maspack.geometry

Class GeometryUtils

java.lang.Object

maspack.geometry.GeometryUtils

public class GeometryUtils
extends java.lang.Object

Utility methods for geometric computation.

Constructor Summary

Constructors

Constructor and Description
GeometryUtils()

Method Summary

Modifier and Type	Method and Description
static double	findNearestPoint(Point3d pr, java.util.List<Point3d> vtxs, boolean closed, Point3d p0, double r0) Finds the nearest point on a polyline to a prescribed point p0.
static double	findPointAtDistance(Point3d pr, java.util.List<Point3d> vtxs, boolean closed, Point3d p0, double dist, double r0) Finds the point on a polyline that is a specified distance dist from a prescribed point p0, within machine precision.
static double	getCharacteristicLength(java.util.Collection<Point3d> pnts) Finds the characteristic length of a collection of points.

Methods inherited from class java.lang.Object

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

Constructor Detail

GeometryUtils

public GeometryUtils()

Method Detail

getCharacteristicLength

public static double getCharacteristicLength(java.util.Collection<Point3d> pnts)

Finds the characteristic length of a collection of points.

Parameters:

pnts - points to query

Returns:

characteristic length

findPointAtDistance

public static double findPointAtDistance(Point3d pr,
                                         java.util.List<Point3d> vtxs,
                                         boolean closed,
                                         Point3d p0,
                                         double dist,
                                         double r0)

Finds the point on a polyline that is a specified distance dist from a prescribed point p0, within machine precision. The polyline is specified by a list of vertices vtxs. Point locations on the polyline are described by a non-negative parameter r, which takes the form

 r = k + s
 

where k is the index of a polyline vertex, and s is a scalar parameter in the range [0,1] that specifies the location along the interval between vertices k and k+1. If the polyline is open, the search for the distance point begins at a location specified by r0 and locations before r0 are ignored. If the polyline is closed, r0 is ignored.

If found, the method will return the point's location parameter r, as well as the point's value in the optional parameter pr if it is not null. If the point is not found, the method will return -1.

It is assumed that no two adjacent vertices on the polyline are identical within machine precision. If they are, an exception will be thrown.

Parameters:

pr - if not null, returns the distance point, if found

vtxs - list of vertices defining the polyline

closed - true if the polyline is closed

p0 - point with respect to which distance should be determined

dist - desired distance from p0

r0 - for open polylines, a non-negative scalar giving the location on the polyline where the search should start. This should be a non-negative scalar whose value is less than or equal to the number of polyline intervals, which will be vtxs.size()-1.

Returns:

location of the distance point on the polyline, if found, or -1.

findNearestPoint

public static double findNearestPoint(Point3d pr,
                                      java.util.List<Point3d> vtxs,
                                      boolean closed,
                                      Point3d p0,
                                      double r0)

Finds the nearest point on a polyline to a prescribed point p0. The polyline is specified by a list of vertices vtxs. Locations on the polyline are described by a non-negative parameter r, which takes the form

 r = k + s
 

where k is the index of a polyline vertex, and s is a scalar parameter in the range [0,1] that specifies the location along the interval between vertices k and k+1. If the polyline is open, the search for the nearest point begins at a location specified by r0 and locations before r0 are ignored. If the polyline is closed, r0 is ignored. The nearest point may not be unique.

The method will return the nearest point's location parameter r, as well as the point's value in the optional parameter pr if it is not null. If the polyline is empty, both r and pr at set to 0.

It is assumed that no two adjacent vertices on the polyline are identical within machine precision. If they are, an exception will be thrown.

Parameters:

pr - if not null, returns the nearest point

vtxs - list of vertices defining the polyline

closed - true if the polyline is closed

p0 - point for which the nearest point should be determined

r0 - for open polylines, a non-negative scalar giving the location on the polyline where the search should start. This should be a non-negative scalar whose value is less than or equal to the number of polyline intervals, which will be vtxs.size()-1.

Returns:

location of the nearest point on the polyline