/**
* Subdivide a list of positions so that no segment is longer then the provided maxLength. Only
* the positions between start and start + count - 1 will be processed.
*
* <p>If needed, new intermediate positions will be created along lines that follow the given
* pathType - one of Polyline.LINEAR, Polyline.RHUMB_LINE or Polyline.GREAT_CIRCLE. All position
* elevations will be either at the terrain surface if followTerrain is true, or interpolated
* according to the original elevations.
*
* @param globe the globe to draw elevations and points from.
* @param positions the original position list
* @param maxLength the maximum length for one segment.
* @param followTerrain true if the positions should be on the terrain surface.
* @param pathType the type of path to use in between two positions.
* @param start the first position indice in the original list.
* @param count how many positions from the original list have to be processed and returned.
* @return a list of positions with no segment longer then maxLength and elevations following
* terrain or not.
*/
protected static ArrayList<? extends Position> subdividePositions(
Globe globe,
ArrayList<? extends Position> positions,
double maxLength,
boolean followTerrain,
String pathType,
int start,
int count) {
if (positions == null || positions.size() < start + count) return positions;
ArrayList<Position> newPositions = new ArrayList<Position>();
// Add first position
Position pos1 = positions.get(start);
if (followTerrain)
newPositions.add(
new Position(pos1, globe.getElevation(pos1.getLatitude(), pos1.getLongitude())));
else newPositions.add(pos1);
for (int i = 1; i < count; i++) {
Position pos2 = positions.get(start + i);
double arcLengthRadians = LatLon.greatCircleDistance(pos1, pos2).radians;
double arcLength = arcLengthRadians * globe.getRadiusAt(LatLon.interpolate(.5, pos1, pos2));
if (arcLength > maxLength) {
// if necessary subdivide segment at regular intervals smaller then maxLength
Angle segmentAzimuth = null;
Angle segmentDistance = null;
int steps = (int) Math.ceil(arcLength / maxLength); // number of intervals - at least two
for (int j = 1; j < steps; j++) {
float s = (float) j / steps;
LatLon destLatLon;
if (pathType.equals(AVKey.LINEAR)) {
destLatLon = LatLon.interpolate(s, pos1, pos2);
} else if (pathType.equals(AVKey.RHUMB_LINE)) {
if (segmentAzimuth == null) {
segmentAzimuth = LatLon.rhumbAzimuth(pos1, pos2);
segmentDistance = LatLon.rhumbDistance(pos1, pos2);
}
destLatLon =
LatLon.rhumbEndPosition(pos1, segmentAzimuth.radians, s * segmentDistance.radians);
} else // GREAT_CIRCLE
{
if (segmentAzimuth == null) {
segmentAzimuth = LatLon.greatCircleAzimuth(pos1, pos2);
segmentDistance = LatLon.greatCircleDistance(pos1, pos2);
}
destLatLon =
LatLon.greatCircleEndPosition(
pos1, segmentAzimuth.radians, s * segmentDistance.radians);
}
// Set elevation
double elevation;
if (followTerrain)
elevation = globe.getElevation(destLatLon.getLatitude(), destLatLon.getLongitude());
else elevation = pos1.elevation * (1 - s) + pos2.elevation * s;
// Add new position
newPositions.add(new Position(destLatLon, elevation));
}
}
// Finally add the segment end position
if (followTerrain)
newPositions.add(
new Position(pos2, globe.getElevation(pos2.getLatitude(), pos2.getLongitude())));
else newPositions.add(pos2);
// Prepare for next segment
pos1 = pos2;
}
return newPositions;
}