/**
* 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();
}
