Killer Game Programming in Java

Responding to Key Presses

KeyBehavior is similar to the KeyBehavior classes I developed for FPShooter3D in Chapter 24 and for Maze3D in Chapter 25. However, this class is given charge of positioning the viewpoint in initViewPosition(), which asks the Landscape object for the origin's coordinates:

    private void initViewPosition(TransformGroup steerTG)
    // place viewpoint at (0,?,0), facing into scene
    {
      Vector3d startPosn = land.getOriginVec();
      // startPosn is (0, <height of floor>, 0)
   
      currLandHeight = startPosn.y;   // store current floor height
      startPosn.y += USER_HEIGHT;     // add user's height
   
      steerTG.getTransform(t3d);      // targetTG not yet available
      t3d.setTranslation(startPosn);  // so use steerTG
      steerTG.setTransform(t3d);
    }

KeyBehaviour needs to know the current floor height to reposition the viewpoint as it moves.

The operations carried out by KeyBehavior can be grouped into three categories:

• Movements requiring floor height information (i.e., moves forward, backward, to the left, and right)

• Movements requiring height offset information (i.e., moves up and down)

• Rotations around the current location (i.e., turns to the left and right)

Rotations don't require floor height data, so are implemented as rotations of ViewPlatform's TransformGroup.

Movements up and down are made more efficient by KeyBehavior storing a zOffset counter which records how many upward moves have been made by the user. Consequently, a move down will only be allowed if zOffset is > 0. The efficiency gain exists because ...