protected void makeTessellatedLocations(
Globe globe, int subdivisions, List<LatLon> locations, List<LatLon> tessellatedLocations) {
ArrayList<Vec4> points = new ArrayList<Vec4>();
for (LatLon ll : locations) {
points.add(globe.computePointFromLocation(ll));
}
//noinspection StringEquality
if (WWMath.computeWindingOrderOfLocations(locations) != AVKey.COUNTER_CLOCKWISE)
Collections.reverse(locations);
Vec4 centerPoint = Vec4.computeAveragePoint(points);
Vec4 surfaceNormal = globe.computeSurfaceNormalAtPoint(centerPoint);
int numPoints = points.size();
float[] coords = new float[3 * numPoints];
for (int i = 0; i < numPoints; i++) {
points.get(i).toFloatArray(coords, 3 * i, 3);
}
GeometryBuilder gb = new GeometryBuilder();
GeometryBuilder.IndexedTriangleArray tessellatedPoints =
gb.tessellatePolygon(0, numPoints, coords, surfaceNormal);
for (int i = 0; i < subdivisions; i++) {
gb.subdivideIndexedTriangleArray(tessellatedPoints);
}
for (int i = 0; i < tessellatedPoints.getVertexCount(); i++) {
Vec4 v = Vec4.fromFloatArray(tessellatedPoints.getVertices(), 3 * i, 3);
tessellatedLocations.add(globe.computePositionFromPoint(v));
}
}
@Override
protected List<Vec4> computeMinimalGeometry(Globe globe, double verticalExaggeration) {
double[] angles = this.computeAngles();
// Angles are equal, fall back to building a closed cylinder.
if (angles == null) return super.computeMinimalGeometry(globe, verticalExaggeration);
double[] radii = this.getRadii();
Matrix transform = this.computeTransform(globe, verticalExaggeration);
GeometryBuilder gb = this.getGeometryBuilder();
int count = gb.getPartialDiskVertexCount(MINIMAL_GEOMETRY_SLICES, MINIMAL_GEOMETRY_LOOPS);
int numCoords = 3 * count;
float[] verts = new float[numCoords];
gb.makePartialDiskVertices(
(float) radii[0],
(float) radii[1], // Inner radius, outer radius.
MINIMAL_GEOMETRY_SLICES,
MINIMAL_GEOMETRY_LOOPS, // Slices, loops,
(float) angles[0],
(float) angles[2], // Start angle, sweep angle.
verts);
List<LatLon> locations = new ArrayList<LatLon>();
for (int i = 0; i < numCoords; i += 3) {
Vec4 v = new Vec4(verts[i], verts[i + 1], verts[i + 2]);
v = v.transformBy4(transform);
locations.add(globe.computePositionFromPoint(v));
}
ArrayList<Vec4> points = new ArrayList<Vec4>();
this.makeExtremePoints(globe, verticalExaggeration, locations, points);
return points;
}
private void makePartialCylinderTerrainConformant(
DrawContext dc,
int slices,
int stacks,
float[] verts,
double[] altitudes,
boolean[] terrainConformant,
Vec4 referenceCenter) {
Globe globe = dc.getGlobe();
Matrix transform = this.computeTransform(dc.getGlobe(), dc.getVerticalExaggeration());
for (int i = 0; i <= slices; i++) {
int index = i * (stacks + 1);
index = 3 * index;
Vec4 vec = new Vec4(verts[index], verts[index + 1], verts[index + 2]);
vec = vec.transformBy4(transform);
Position p = globe.computePositionFromPoint(vec);
for (int j = 0; j <= stacks; j++) {
double elevation = altitudes[j];
if (terrainConformant[j])
elevation += this.computeElevationAt(dc, p.getLatitude(), p.getLongitude());
vec = globe.computePointFromPosition(p.getLatitude(), p.getLongitude(), elevation);
index = j + i * (stacks + 1);
index = 3 * index;
verts[index] = (float) (vec.x - referenceCenter.x);
verts[index + 1] = (float) (vec.y - referenceCenter.y);
verts[index + 2] = (float) (vec.z - referenceCenter.z);
}
}
}
private void makePartialDiskTerrainConformant(
DrawContext dc,
int numCoords,
float[] verts,
double altitude,
boolean terrainConformant,
Vec4 referenceCenter) {
Globe globe = dc.getGlobe();
Matrix transform = this.computeTransform(dc.getGlobe(), dc.getVerticalExaggeration());
for (int i = 0; i < numCoords; i += 3) {
Vec4 vec = new Vec4(verts[i], verts[i + 1], verts[i + 2]);
vec = vec.transformBy4(transform);
Position p = globe.computePositionFromPoint(vec);
double elevation = altitude;
if (terrainConformant)
elevation += this.computeElevationAt(dc, p.getLatitude(), p.getLongitude());
vec = globe.computePointFromPosition(p.getLatitude(), p.getLongitude(), elevation);
verts[i] = (float) (vec.x - referenceCenter.x);
verts[i + 1] = (float) (vec.y - referenceCenter.y);
verts[i + 2] = (float) (vec.z - referenceCenter.z);
}
}
protected boolean areShapesIntersecting(Airspace a1, Airspace a2) {
if ((a1 instanceof SphereAirspace) && (a2 instanceof SphereAirspace)) {
SphereAirspace s1 = (SphereAirspace) a1;
SphereAirspace s2 = (SphereAirspace) a2;
LatLon location1 = s1.getLocation();
LatLon location2 = s2.getLocation();
double altitude1 = s1.getAltitudes()[0];
double altitude2 = s2.getAltitudes()[0];
boolean terrainConforming1 = s1.isTerrainConforming()[0];
boolean terrainConforming2 = s2.isTerrainConforming()[0];
// We have to compute the 3D coordinates of the sphere's center ourselves here.
Vec4 p1 =
terrainConforming1
? this.getSurfacePoint(location1, altitude1)
: this.getPoint(location1, altitude1);
Vec4 p2 =
terrainConforming2
? this.getSurfacePoint(location2, altitude2)
: this.getPoint(location2, altitude2);
double r1 = s1.getRadius();
double r2 = s2.getRadius();
double d = p1.distanceTo3(p2);
return d <= (r1 + r2);
}
return false;
}
/**
* Performs one line of sight calculation between the reference position and a specified grid
* position.
*
* @param gridPosition the grid position.
* @throws InterruptedException if the operation is interrupted.
*/
protected void performIntersection(Position gridPosition) throws InterruptedException {
// Intersect the line between this grid point and the selected position.
Intersection[] intersections = this.terrain.intersect(this.referencePosition, gridPosition);
if (intersections == null || intersections.length == 0) {
// No intersection, so the line goes from the center to the grid point.
this.sightLines.add(new Position[] {this.referencePosition, gridPosition});
return;
}
// Only the first intersection is shown.
Vec4 iPoint = intersections[0].getIntersectionPoint();
Vec4 gPoint =
terrain.getSurfacePoint(
gridPosition.getLatitude(), gridPosition.getLongitude(), gridPosition.getAltitude());
// Check to see whether the intersection is beyond the grid point.
if (iPoint.distanceTo3(this.referencePoint) >= gPoint.distanceTo3(this.referencePoint)) {
// Intersection is beyond the grid point; the line goes from the center to the grid point.
this.addSightLine(this.referencePosition, gridPosition);
return;
}
// Compute the position corresponding to the intersection.
Position iPosition = this.terrain.getGlobe().computePositionFromPoint(iPoint);
// The sight line goes from the user-selected position to the intersection position.
this.addSightLine(this.referencePosition, new Position(iPosition, 0));
// Keep track of the intersection positions.
this.addIntersectionPosition(iPosition);
this.updateProgress();
}
public static void main(String[] args) {
BarycentricPlanarShape bc = new BarycentricQuadrilateral(i0, i1, i2, i3);
for (Vec4 point : testPoints) {
double[] w = bc.getBarycentricCoords(point);
Vec4 p = bc.getPoint(w);
double[] uv = bc.getBilinearCoords(w[1], w[2]);
System.out.printf(
"%s, %s: ( %f, %f, %f) : ( %f, %f), %s\n",
point, p, w[0], w[1], w[2], uv[0], uv[1], p.equals(point) ? "true" : "false");
}
//
// BarycentricPlanarShape bc = new BarycentricQuadrilateral(new Vec4(4, 3, 0), new
// Vec4(7, 1, 0),
// new Vec4(10, 5, 0), new Vec4(7, 7, 0));
//
// ArrayList<Vec4> points = makePoints(0, 0, 14, 10);
// for (Vec4 point : points)
// {
// double[] w = bc.getBarycentricCoords(point);
// Vec4 p = bc.getPoint(w);
// double[] uv = bc.getBilinearCoords(w[1], w[2]);
//
// System.out.printf("%s, %s: ( %f, %f, %f) : ( %f, %f), %s\n",
// point, p, w[0], w[1], w[2], uv[0], uv[1], p.equals(point) ? "true" : "false");
// }
}
private void makeRadialWallTerrainConformant(
DrawContext dc,
int pillars,
int stacks,
float[] verts,
double[] altitudes,
boolean[] terrainConformant,
Vec4 referenceCenter) {
Globe globe = dc.getGlobe();
Matrix transform = this.computeTransform(dc.getGlobe(), dc.getVerticalExaggeration());
for (int p = 0; p <= pillars; p++) {
int index = p;
index = 3 * index;
Vec4 vec = new Vec4(verts[index], verts[index + 1], verts[index + 2]);
vec = vec.transformBy4(transform);
Position pos = globe.computePositionFromPoint(vec);
for (int s = 0; s <= stacks; s++) {
double elevation = altitudes[s];
if (terrainConformant[s])
elevation += this.computeElevationAt(dc, pos.getLatitude(), pos.getLongitude());
vec = globe.computePointFromPosition(pos.getLatitude(), pos.getLongitude(), elevation);
index = p + s * (pillars + 1);
index = 3 * index;
verts[index] = (float) (vec.x - referenceCenter.x);
verts[index + 1] = (float) (vec.y - referenceCenter.y);
verts[index + 2] = (float) (vec.z - referenceCenter.z);
}
}
}
protected void requestTile(DrawContext dc, Tile tile) {
Vec4 centroid = dc.getGlobe().computePointFromPosition(tile.getSector().getCentroid(), 0);
if (this.getReferencePoint() != null)
tile.setPriority(centroid.distanceTo3(this.getReferencePoint()));
RequestTask task = new RequestTask(tile, this);
this.getRequestQ().add(task);
}
protected static boolean isNameVisible(
DrawContext dc, PlaceNameService service, Position namePosition) {
double elevation = dc.getVerticalExaggeration() * namePosition.getElevation();
Vec4 namePoint =
dc.getGlobe()
.computePointFromPosition(
namePosition.getLatitude(), namePosition.getLongitude(), elevation);
Vec4 eyeVec = dc.getView().getEyePoint();
double dist = eyeVec.distanceTo3(namePoint);
return dist >= service.getMinDisplayDistance() && dist <= service.getMaxDisplayDistance();
}
private void makeCap(
DrawContext dc,
GeometryBuilder.IndexedTriangleArray ita,
double altitude,
boolean terrainConformant,
int orientation,
Matrix locationTransform,
Vec4 referenceCenter,
int indexPos,
int[] indices,
int vertexPos,
float[] vertices,
float[] normals) {
GeometryBuilder gb = this.getGeometryBuilder();
Globe globe = dc.getGlobe();
int indexCount = ita.getIndexCount();
int vertexCount = ita.getVertexCount();
int[] locationIndices = ita.getIndices();
float[] locationVerts = ita.getVertices();
this.copyIndexArray(
indexCount,
(orientation == GeometryBuilder.INSIDE),
locationIndices,
vertexPos,
indexPos,
indices);
for (int i = 0; i < vertexCount; i++) {
int index = 3 * i;
Vec4 vec = new Vec4(locationVerts[index], locationVerts[index + 1], locationVerts[index + 2]);
vec = vec.transformBy4(locationTransform);
Position pos = globe.computePositionFromPoint(vec);
vec =
this.computePointFromPosition(
dc, pos.getLatitude(), pos.getLongitude(), altitude, terrainConformant);
index = 3 * (vertexPos + i);
vertices[index] = (float) (vec.x - referenceCenter.x);
vertices[index + 1] = (float) (vec.y - referenceCenter.y);
vertices[index + 2] = (float) (vec.z - referenceCenter.z);
}
gb.makeIndexedTriangleArrayNormals(
indexPos, indexCount, indices, vertexPos, vertexCount, vertices, normals);
}
private void makeSectionVertices(
DrawContext dc,
int locationPos,
float[] locations,
double[] altitude,
boolean[] terrainConformant,
int subdivisions,
Matrix locationTransform,
Vec4 referenceCenter,
int vertexPos,
float[] vertices) {
GeometryBuilder gb = this.getGeometryBuilder();
int numPoints = gb.getSubdivisionPointsVertexCount(subdivisions);
Globe globe = dc.getGlobe();
int index1 = 3 * locationPos;
int index2 = 3 * (locationPos + 1);
float[] locationVerts = new float[3 * numPoints];
gb.makeSubdivisionPoints(
locations[index1],
locations[index1 + 1],
locations[index1 + 2],
locations[index2],
locations[index2 + 1],
locations[index2 + 2],
subdivisions,
locationVerts);
for (int i = 0; i < numPoints; i++) {
int index = 3 * i;
Vec4 vec = new Vec4(locationVerts[index], locationVerts[index + 1], locationVerts[index + 2]);
vec = vec.transformBy4(locationTransform);
Position pos = globe.computePositionFromPoint(vec);
for (int j = 0; j < 2; j++) {
vec =
this.computePointFromPosition(
dc, pos.getLatitude(), pos.getLongitude(), altitude[j], terrainConformant[j]);
index = 2 * i + j;
index = 3 * (vertexPos + index);
vertices[index] = (float) (vec.x - referenceCenter.x);
vertices[index + 1] = (float) (vec.y - referenceCenter.y);
vertices[index + 2] = (float) (vec.z - referenceCenter.z);
}
}
}
protected Extent computeExtent(Globe globe, double verticalExaggeration) {
List<Vec4> points = this.computeMinimalGeometry(globe, verticalExaggeration);
if (points == null || points.isEmpty()) return null;
// Add a point at the center of this polygon to the points used to compute its extent. The
// center point captures
// the curvature of the globe when the polygon's minimal geometry only contain any points near
// the polygon's
// edges.
Vec4 centerPoint = Vec4.computeAveragePoint(points);
LatLon centerLocation = globe.computePositionFromPoint(centerPoint);
this.makeExtremePoints(globe, verticalExaggeration, Arrays.asList(centerLocation), points);
return Box.computeBoundingBox(points);
}
/**
* Compute points on either side of a line segment. This method requires a point on the line, and
* either a next point, previous point, or both.
*
* @param point Center point about which to compute side points.
* @param prev Previous point on the line. May be null if {@code next} is non-null.
* @param next Next point on the line. May be null if {@code prev} is non-null.
* @param leftPositions Left position will be added to this list.
* @param rightPositions Right position will be added to this list.
* @param halfWidth Distance from the center line to the left or right lines.
* @param globe Current globe.
*/
protected void generateParallelPoints(
Vec4 point,
Vec4 prev,
Vec4 next,
List<Position> leftPositions,
List<Position> rightPositions,
double halfWidth,
Globe globe) {
if ((point == null) || (prev == null && next == null)) {
String message = Logging.getMessage("nullValue.PointIsNull");
Logging.logger().severe(message);
throw new IllegalArgumentException(message);
}
if (leftPositions == null || rightPositions == null) {
String message = Logging.getMessage("nullValue.PositionListIsNull");
Logging.logger().severe(message);
throw new IllegalArgumentException(message);
}
if (globe == null) {
String message = Logging.getMessage("nullValue.GlobeIsNull");
Logging.logger().severe(message);
throw new IllegalArgumentException(message);
}
Vec4 offset;
Vec4 normal = globe.computeSurfaceNormalAtPoint(point);
// Compute vector in the direction backward along the line.
Vec4 backward = (prev != null) ? prev.subtract3(point) : point.subtract3(next);
// Compute a vector perpendicular to segment BC, and the globe normal vector.
Vec4 perpendicular = backward.cross3(normal);
double length;
// If both next and previous points are supplied then calculate the angle that bisects the angle
// current, next, prev.
if (next != null && prev != null && !Vec4.areColinear(prev, point, next)) {
// Compute vector in the forward direction.
Vec4 forward = next.subtract3(point);
// Calculate the vector that bisects angle ABC.
offset = forward.normalize3().add3(backward.normalize3());
offset = offset.normalize3();
// Compute the scalar triple product of the vector BC, the normal vector, and the offset
// vector to
// determine if the offset points to the left or the right of the control line.
double tripleProduct = perpendicular.dot3(offset);
if (tripleProduct < 0) {
offset = offset.multiply3(-1);
}
// Determine the length of the offset vector that will keep the left and right lines parallel
// to the control
// line.
Angle theta = backward.angleBetween3(offset);
if (!Angle.ZERO.equals(theta)) length = halfWidth / theta.sin();
else length = halfWidth;
} else {
offset = perpendicular.normalize3();
length = halfWidth;
}
offset = offset.multiply3(length);
// Determine the left and right points by applying the offset.
Vec4 ptRight = point.add3(offset);
Vec4 ptLeft = point.subtract3(offset);
// Convert cartesian points to geographic.
Position posLeft = globe.computePositionFromPoint(ptLeft);
Position posRight = globe.computePositionFromPoint(ptRight);
leftPositions.add(posLeft);
rightPositions.add(posRight);
}
public static double[] invertBilinear(Vec4 U, Vec4 X, Vec4 Y, Vec4 Z, Vec4 W) {
Vec4 s1 = W.subtract3(X);
Vec4 s2 = Z.subtract3(Y);
Vec4 UminX = U.subtract3(X);
Vec4 UminY = U.subtract3(Y);
Vec4 normal = Z.subtract3(X).cross3(W.subtract3(Y));
double A = s1.cross3(s2).dot3(normal);
double B = s2.cross3(UminX).dot3(normal) - s1.cross3(UminY).dot3(normal);
double C = UminX.cross3(UminY).dot3(normal);
double descriminant = B * B - 4d * A * C;
if (descriminant < 0) return null;
descriminant = Math.sqrt(descriminant);
double beta = B > 0 ? (-B - descriminant) / (2d * A) : 2d * C / (-B + descriminant);
Vec4 Sbeta1 = Vec4.mix3(beta, X, W);
Vec4 Sbeta2 = Vec4.mix3(beta, Y, Z);
double alpha =
U.subtract3(Sbeta1).dot3(Sbeta2.subtract3(Sbeta1)) / Sbeta2.subtract3(Sbeta1).dotSelf3();
return new double[] {alpha, beta};
}
/**
* 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);
}
protected int computeCartesianPolygon(
Globe globe,
List<? extends LatLon> locations,
List<Boolean> edgeFlags,
Vec4[] points,
Boolean[] edgeFlagArray,
Matrix[] transform) {
if (globe == null) {
String message = Logging.getMessage("nullValue.GlobeIsNull");
Logging.logger().severe(message);
throw new IllegalArgumentException(message);
}
if (locations == null) {
String message = "nullValue.LocationsIsNull";
Logging.logger().severe(message);
throw new IllegalArgumentException(message);
}
if (points == null) {
String message = "nullValue.LocationsIsNull";
Logging.logger().severe(message);
throw new IllegalArgumentException(message);
}
if (points.length < (1 + locations.size())) {
String message =
Logging.getMessage(
"generic.ArrayInvalidLength", "points.length < " + (1 + locations.size()));
Logging.logger().severe(message);
throw new IllegalArgumentException(message);
}
if (transform == null) {
String message = "nullValue.TransformIsNull";
Logging.logger().severe(message);
throw new IllegalArgumentException(message);
}
if (transform.length < 1) {
String message = Logging.getMessage("generic.ArrayInvalidLength", "transform.length < 1");
Logging.logger().severe(message);
throw new IllegalArgumentException(message);
}
// Allocate space to hold the list of locations and location vertices.
int locationCount = locations.size();
// Compute the cartesian points for each location.
for (int i = 0; i < locationCount; i++) {
LatLon ll = locations.get(i);
points[i] = globe.computePointFromPosition(ll.getLatitude(), ll.getLongitude(), 0.0);
if (edgeFlagArray != null) edgeFlagArray[i] = (edgeFlags != null) ? edgeFlags.get(i) : true;
}
// Compute the average of the cartesian points.
Vec4 centerPoint = Vec4.computeAveragePoint(Arrays.asList(points));
// Test whether the polygon is closed. If it is not closed, repeat the first vertex.
if (!points[0].equals(points[locationCount - 1])) {
points[locationCount] = points[0];
if (edgeFlagArray != null) edgeFlagArray[locationCount] = edgeFlagArray[0];
locationCount++;
}
// Compute a transform that will map the cartesian points to a local coordinate system centered
// at the average
// of the points and oriented with the globe surface.
Position centerPos = globe.computePositionFromPoint(centerPoint);
Matrix tx = globe.computeSurfaceOrientationAtPosition(centerPos);
Matrix txInv = tx.getInverse();
// Map the cartesian points to a local coordinate space.
for (int i = 0; i < locationCount; i++) {
points[i] = points[i].transformBy4(txInv);
}
transform[0] = tx;
return locationCount;
}
/**
* 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));
}
/**
* 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);
}