/**
* Determines the orientation of a LineSegment relative to this segment. The concept of
* orientation is specified as follows: Given two line segments A and L,
*
* <ul
* <li>
* A is to the left of a segment L if A lies wholly in the closed half-plane lying to the left
* of L
* <li>A is to the right of a segment L if A lies wholly in the closed half-plane lying to the
* right of L
* <li>otherwise, A has indeterminate orientation relative to L. This happens if A is collinear
* with L or if A crosses the line determined by L.
* </ul>
*
* @param seg the LineSegment to compare
* @return 1 if <code>seg</code> is to the left of this segment
* @return -1 if <code>seg</code> is to the right of this segment
* @return 0 if <code>seg</code> is collinear to or crosses this segment
*/
public int orientationIndex(LineSegment seg) {
int orient0 = CGAlgorithms.orientationIndex(p0, p1, seg.p0);
int orient1 = CGAlgorithms.orientationIndex(p0, p1, seg.p1);
// this handles the case where the points are L or collinear
if (orient0 >= 0 && orient1 >= 0) return Math.max(orient0, orient1);
// this handles the case where the points are R or collinear
if (orient0 <= 0 && orient1 <= 0) return Math.max(orient0, orient1);
// points lie on opposite sides ==> indeterminate orientation
return 0;
}
/**
* Computes the {@link Coordinate} that lies a given fraction along the line defined by this
* segment and offset from the segment by a given distance. A fraction of <code>0.0</code> offsets
* from the start point of the segment; a fraction of <code>1.0</code> offsets from the end point
* of the segment. The computed point is offset to the left of the line if the offset distance is
* positive, to the right if negative.
*
* @param segmentLengthFraction the fraction of the segment length along the line
* @param offsetDistance the distance the point is offset from the segment (positive is to the
* left, negative is to the right)
* @return the point at that distance and offset
* @throws IllegalStateException if the segment has zero length
*/
public Coordinate pointAlongOffset(double segmentLengthFraction, double offsetDistance) {
// the point on the segment line
double segx = p0.x + segmentLengthFraction * (p1.x - p0.x);
double segy = p0.y + segmentLengthFraction * (p1.y - p0.y);
double dx = p1.x - p0.x;
double dy = p1.y - p0.y;
double len = Math.sqrt(dx * dx + dy * dy);
double ux = 0.0;
double uy = 0.0;
if (offsetDistance != 0.0) {
if (len <= 0.0)
throw new IllegalStateException("Cannot compute offset from zero-length line segment");
// u is the vector that is the length of the offset, in the direction of the segment
ux = offsetDistance * dx / len;
uy = offsetDistance * dy / len;
}
// the offset point is the seg point plus the offset vector rotated 90 degrees CCW
double offsetx = segx - uy;
double offsety = segy + ux;
Coordinate coord = new Coordinate(offsetx, offsety);
return coord;
}
/**
* Gets the minimum X ordinate.
*
* @return the minimum X ordinate
*/
public double minX() {
return Math.min(p0.x, p1.x);
}
/**
* Computes the angle that the vector defined by this segment makes with the X-axis. The angle
* will be in the range [ -PI, PI ] radians.
*
* @return the angle this segment makes with the X-axis (in radians)
*/
public double angle() {
return Math.atan2(p1.y - p0.y, p1.x - p0.x);
}
/**
* Gets the maximum Y ordinate.
*
* @return the maximum Y ordinate
*/
public double maxY() {
return Math.max(p0.y, p1.y);
}
/**
* Gets the minimum Y ordinate.
*
* @return the minimum Y ordinate
*/
public double minY() {
return Math.min(p0.y, p1.y);
}
/**
* Gets the maximum X ordinate.
*
* @return the maximum X ordinate
*/
public double maxX() {
return Math.max(p0.x, p1.x);
}
