gov.nasa.worldwind.util.combine

Interface Combinable

All Known Implementing Classes:

AbstractSurfaceShape, ContourList, DirectedSurfacePolyline, KMLSurfacePolygonImpl, SectorSelector.RegionShape, SurfaceBox, SurfaceCircle, SurfaceEllipse, SurfaceMultiPolygon, SurfacePolygon, SurfacePolygons, SurfacePolyline, SurfacePolylines, SurfaceQuad, SurfaceSector, SurfaceSquare

public interface Combinable

Interface for shapes that can be combined into a complex set of contours by using boolean operations. Combinable shapes implement the single method combine(CombineContext). This method is typically called by a controller that operates on one or more combinable shapes and implements the boolean operation that is applied to those shapes, such as ShapeCombiner. When combine is called, the Combinable draws its contours using the GLU tessellator attached to the provided CombineContext. When the CombineContext is in bounding sector mode, the Combinable adds its geographic bounding sector to the CombineContext's bounding sector list.

Drawing Contours

Shapes are combined into a complex set of contours by drawing their individual contours using the GLU tessellator attached to a CombineContext. A controller that implements the boolean operation configures the CombineContext then calls combine on each shape. It is the responsibility of the controller to configure the GLU tessellator and define the beginning and end of a polygon. Shapes define the contours and vertices that represent the shape's geometry. Each vertex must be a 3-tuple in geographic coordinates ordered as (longitude, latitude, 0). The winding order of each contour defines whether the contour is an exterior region or an interior region. Counterclockwise contours define the outer boundaries, and clockwise contours define holes or inner boundaries. Contours may be nested, but a nested contour must be oriented oppositely from the contour that contains it.

Bounding Sector Mode

CombineContext may be configured in bounding sector mode by returning true from isBoundingSectorMode(). When combine is called in this mode, a shape adds its geographic bounding sector to the context by calling addBoundingSector(Sector). CombineContext assumes that each shape either contributes one bounding sector or does not contribute anything.

Example Implementation

 public class CombinableSector implements Combinable
 {
     protected Sector sector = Sector.fromDegrees(-10, 10, -10, 10);

     public void combine(CombineContext cc)
     {
         if (cc.isBoundingSectorMode())
             this.combineBounds(cc);
         else
             this.combineContours(cc);
     }

     protected void combineBounds(CombineContext cc)
     {
         cc.addBoundingSector(this.sector);
     }

     protected void combineContours(CombineContext cc)
     {
         if (!cc.getSector().intersects(this.sector))
             return;  // the sector does not intersect the context's region of interest

         this.doCombineContours(cc);
     }

     protected void doCombineContours(CombineContext cc)
     {
         GLUtessellator tess = cc.getTessellator();

         try
         {
             GLU.gluTessBeginContour(tess);

             for (LatLon location : this.sector) // counter clockwise iteration of the sector's four corners
             {
                 double[] vertex = {location.longitude.degrees, location.latitude.degrees, 0};
                 GLU.gluTessVertex(tess, vertex, 0, vertex); // longitude,latitude,0 -> x,y,z
             }
         }
         finally
         {
             GLU.gluTessEndContour(tess);
         }
     }
 }
 

See Also:

CombineContext, ShapeCombiner

Method Summary

Modifier and Type	Method and Description
void	combine(CombineContext cc) Causes this Combinable to draw its contours using the GLU tessellator attached to the provided CombineContext.

Method Detail

combine

void combine(CombineContext cc)

Causes this Combinable to draw its contours using the GLU tessellator attached to the provided CombineContext. When the CombineContext is in bounding sector mode, this adds the Combinable's geographic bounding sector to the CombineContext's bounding sector list. See the interface documentation for more information.

Parameters:

cc - the CombineContext to be used.

Throws:

IllegalArgumentException - if the CombineContext is null.

See Also:

CombineContext