/**
* Compute the positions of the arrow head of the graphic's legs.
*
* @param dc Current draw context
* @param base Position of the arrow's starting point.
* @param tip Position of the arrow head tip.
* @param arrowLength Length of the arrowhead as a fraction of the total line length.
* @param arrowAngle Angle of the arrow head.
* @return Positions required to draw the arrow head.
*/
protected List<Position> computeArrowheadPositions(
DrawContext dc, Position base, Position tip, double arrowLength, Angle arrowAngle) {
// Build a triangle to represent the arrowhead. The triangle is built from two vectors, one
// parallel to the
// segment, and one perpendicular to it.
Globe globe = dc.getGlobe();
Vec4 ptA = globe.computePointFromPosition(base);
Vec4 ptB = globe.computePointFromPosition(tip);
// Compute parallel component
Vec4 parallel = ptA.subtract3(ptB);
Vec4 surfaceNormal = globe.computeSurfaceNormalAtPoint(ptB);
// Compute perpendicular component
Vec4 perpendicular = surfaceNormal.cross3(parallel);
double finalArrowLength = arrowLength * parallel.getLength3();
double arrowHalfWidth = finalArrowLength * arrowAngle.tanHalfAngle();
perpendicular = perpendicular.normalize3().multiply3(arrowHalfWidth);
parallel = parallel.normalize3().multiply3(finalArrowLength);
// Compute geometry of direction arrow
Vec4 vertex1 = ptB.add3(parallel).add3(perpendicular);
Vec4 vertex2 = ptB.add3(parallel).subtract3(perpendicular);
return TacticalGraphicUtil.asPositionList(globe, vertex1, vertex2, ptB);
}
/**
* Determine the positions that make up the arrowhead.
*
* @param dc Current draw context.
* @param startPosition Position of the arrow's base.
* @param endPosition Position of the arrow head tip.
* @return Positions that define the arrowhead.
*/
protected List<Position> computeArrowheadPositions(
DrawContext dc, Position startPosition, Position endPosition) {
Globe globe = dc.getGlobe();
// Arrowhead looks like this:
// _
// A\ | 1/2 width
// ________B\ _|
// Pt. 1 /
// C/
// | |
// Length
Vec4 p1 = globe.computePointFromPosition(startPosition);
Vec4 pB = globe.computePointFromPosition(endPosition);
// Find vector in the direction of the arrow
Vec4 vB1 = p1.subtract3(pB);
double arrowLengthFraction = this.getArrowLength();
// Find the point at the base of the arrowhead
Vec4 arrowBase = pB.add3(vB1.multiply3(arrowLengthFraction));
Vec4 normal = globe.computeSurfaceNormalAtPoint(arrowBase);
// Compute the length of the arrowhead
double arrowLength = vB1.getLength3() * arrowLengthFraction;
double arrowHalfWidth = arrowLength * this.getArrowAngle().tanHalfAngle();
// Compute a vector perpendicular to the segment and the normal vector
Vec4 perpendicular = vB1.cross3(normal);
perpendicular = perpendicular.normalize3().multiply3(arrowHalfWidth);
// Find points A and C
Vec4 pA = arrowBase.add3(perpendicular);
Vec4 pC = arrowBase.subtract3(perpendicular);
return TacticalGraphicUtil.asPositionList(globe, pA, pB, pC);
}
/**
* Determines whether this sector intersects the specified geographic line segment. The line
* segment is specified by a begin location and an end location. The locations are are assumed to
* be connected by a linear path in geographic space. This returns true if any location along that
* linear path intersects this sector, including the begin and end locations.
*
* @param begin the line segment begin location.
* @param end the line segment end location.
* @return true <code>true</code> if this sector intersects the line segment, otherwise <code>
* false</code>.
* @throws IllegalArgumentException if either the begin location or the end location is null.
*/
public boolean intersectsSegment(LatLon begin, LatLon end) {
if (begin == null) {
throw new IllegalArgumentException("Begin Is Null");
}
if (end == null) {
throw new IllegalArgumentException("End Is Null");
}
Vec4 segmentBegin = new Vec4(begin.getLongitude().degrees, begin.getLatitude().degrees, 0);
Vec4 segmentEnd = new Vec4(end.getLongitude().degrees, end.getLatitude().degrees, 0);
Vec4 tmp = segmentEnd.subtract3(segmentBegin);
Vec4 segmentCenter = segmentBegin.add3(segmentEnd).divide3(2);
Vec4 segmentDirection = tmp.normalize3();
double segmentExtent = tmp.getLength3() / 2.0;
LatLon centroid = this.getCentroid();
Vec4 boxCenter = new Vec4(centroid.getLongitude().degrees, centroid.getLatitude().degrees, 0);
double boxExtentX = this.getDeltaLonDegrees() / 2.0;
double boxExtentY = this.getDeltaLatDegrees() / 2.0;
Vec4 diff = segmentCenter.subtract3(boxCenter);
if (Math.abs(diff.x) > (boxExtentX + segmentExtent * Math.abs(segmentDirection.x))) {
return false;
}
if (Math.abs(diff.y) > (boxExtentY + segmentExtent * Math.abs(segmentDirection.y))) {
return false;
}
//noinspection SuspiciousNameCombination
Vec4 segmentPerp = new Vec4(segmentDirection.y, -segmentDirection.x, 0);
return Math.abs(segmentPerp.dot3(diff))
<= (boxExtentX * Math.abs(segmentPerp.x) + boxExtentY * Math.abs(segmentPerp.y));
}
