Picking - Interactive Web-Based Virtual Reality with Java 3D - page 190

Figure 2. First code segment for PickBehaviour.java

1. import java.applet.Applet;
2. import java.awt.BorderLayout;
3. import java.awt.Frame;
4. import com.sun.j3d.utils.applet.MainFrame;
5. import com.sun.j3d.utils.geometry.*;
6. import com.sun.j3d.utils.universe.*;
7. import com.sun.j3d.utils.picking.behaviors.*;
8. import javax.media.j3d.*;
9. import javax.vecmath.*;
10. import java.awt.event.*;
11. import java.util.Enumeration;
12. import com.sun.j3d.utils.behaviors.keyboard.*;
13.
14. public class pickApp extends Applet
15. {
16. Shape3D Landscape()

17. {

18. LineArray landGeom = new LineArray(44, GeometryArray.COORDINATES |

19. GeometryArray.COLOR_3);

20. float l = -100.0f;

21. for(int c = 0; c < 44; c+=4)

22. {

23. landGeom.setCoordinate( c+0, new Point3f( -100.0f, 0.0f, l ));

24. landGeom.setCoordinate( c+1, new Point3f( 100.0f, 0.0f, l ));

25. landGeom.setCoordinate( c+2, new Point3f( l , 0.0f, -100.0f ));

26. landGeom.setCoordinate( c+3, new Point3f( l , 0.0f, 100.0f ));

27. l += 10.0f;

28. }

29.
30.

Color3f c = new Color3f(0.1f, 0.8f, 0.1f);

31. for(int i = 0; i < 44; i++) landGeom.setColor( i, c);

32.
33. return new Shape3D(landGeom);

34. }

35.

they are related to one another. This is described below and shows the processing and flow
involved in a typical picking operation:

• PickTool: This is the base class in picking, and defines the tool that will be used in

the process. The associated method will return a PickResult object for each object
picked.

• PickCanvas: This is a subclass of PickTool for the purpose of simplifying picking

based on mouse events from a canvas, and allows for picking using positional loca-
tions on a canvas through the generation of appropriate pick shape.