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;
    }
  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();
  }