examineviewerbehavior.java

详细介绍Java 3D编程的一本电子书

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.media.j3d.*;
import javax.vecmath.*;


/**
 * ExamineViewerBehavior
 *
 * @version		1.0, 98/04/16
 **/

/**
 * Wakeup on mouse button presses, releases, and mouse movements and
 * generate transforms in an "examination style" that enables the user
 * to rotate, translation, and zoom an object as if it is held at
 * arm's length.  Such an examination style is similar to the "Examine"
 * navigation type used by VRML browsers.
 *
 * The behavior maps mouse drags to different transforms depending
 * upon the mosue button held down:
 *
 *   Button 1 (left)
 *     Horizontal movement --> Y-axis rotation
 *     Vertical movement --> X-axis rotation
 *
 *   Button 2 (middle)
 *     Horizontal movement --> nothing
 *     Vertical movement --> Z-axis translation
 *
 *   Button 3 (right)
 *     Horizontal movement --> X-axis translation
 *     Vertical movement --> Y-axis translation
 *
 * To support systems with 2 or 1 mouse buttons, the following
 * alternate mappings are supported while dragging with any mouse
 * button held down and zero or more keyboard modifiers held down:
 *
 *   No modifiers = Button 1
 *   ALT = Button 2
 *   Meta = Button 3
 *   Control = Button 3
 *
 * The behavior automatically modifies a TransformGroup provided
 * to the constructor.  The TransformGroup's transform can be set
 * at any time by the application or other behaviors to cause the
 * examine rotation and translation to be reset.
 */

// This class is inspired by the MouseBehavior, MouseRotate,
// MouseTranslate, and MouseZoom utility behaviors provided with
// Java 3D.  This class differs from those utilities in that it:
//
//    (a) encapsulates all three behaviors into one in order to
//        enforce a specific "Examine" symantic
//
//    (b) supports set/get of the rotation and translation factors
//        that control the speed of movement.
//
//    (c) supports the "Control" modifier as an alternative to the
//        "Meta" modifier not present on PC, Mac, and most non-Sun
//        keyboards.  This makes button3 behavior usable on PCs,
//        Macs, and other systems with fewer than 3 mouse buttons.

public class ExamineViewerBehavior
	extends ViewerBehavior
{
	// Previous cursor location
	protected int previousX = 0;
	protected int previousY = 0;

	// Saved standard cursor
	protected Cursor savedCursor = null;


	/**
	 * Construct an examine behavior that listens to mouse movement
	 * and button presses to generate rotation and translation
	 * transforms written into a transform group given later
	 * with the setTransformGroup( ) method.
	 */
	public ExamineViewerBehavior( )
	{
		super( );
	}


	/**
	 * Construct an examine behavior that listens to mouse movement
	 * and button presses to generate rotation and translation
	 * transforms written into a transform group given later
	 * with the setTransformGroup( ) method.
	 *
	 * @param parent The AWT Component that contains the area
	 * generating mouse events.
	 */
	public ExamineViewerBehavior( Component parent )
	{
		super( parent );
	}


	/**
	 * Construct an examine behavior that listens to mouse movement
	 * and button presses to generate rotation and translation
	 * transforms written into the given transform group.
	 *
	 * @param transformGroup The transform group to be modified
	 * by the behavior.
	 */
	public ExamineViewerBehavior( TransformGroup transformGroup )
	{
		super( );
		subjectTransformGroup = transformGroup;
	}


	/**
	 * Construct an examine behavior that listens to mouse movement
	 * and button presses to generate rotation and translation
	 * transforms written into the given transform group.
	 *
	 * @param transformGroup The transform group to be modified
	 * by the behavior.
	 * @param parent The AWT Component that contains the area
	 * generating mouse events.
	 */
	public ExamineViewerBehavior( TransformGroup transformGroup,
		Component parent )
	{
		super( parent );
		subjectTransformGroup = transformGroup;
	}


	/**
	 * Respond to a button1 event (press, release, or drag).
	 *
	 * @param mouseEvent A MouseEvent to respond to.
	 */
	public void onButton1( MouseEvent mev )
	{
		if ( subjectTransformGroup == null )
			return;

		int x = mev.getX( );
		int y = mev.getY( );

		if ( mev.getID( ) == MouseEvent.MOUSE_PRESSED )
		{
			// Mouse button pressed:  record position
			previousX = x;
			previousY = y;

			// Change to a "move" cursor
			if ( parentComponent != null )
			{
				savedCursor = parentComponent.getCursor( );
				parentComponent.setCursor(
					Cursor.getPredefinedCursor( Cursor.HAND_CURSOR ) );
			}
			return;
		}
		if ( mev.getID( ) == MouseEvent.MOUSE_RELEASED )
		{
			// Mouse button released:  do nothing

			// Switch the cursor back
			if ( parentComponent != null )
				parentComponent.setCursor( savedCursor );
			return;
		}

		//
		// Mouse moved while button down:  create a rotation
		//
		// Compute the delta in X and Y from the previous
		// position.  Use the delta to compute rotation
		// angles with the mapping:
		//
		//   positive X mouse delta --> positive Y-axis rotation
		//   positive Y mouse delta --> positive X-axis rotation
		//
		// where positive X mouse movement is to the right, and
		// positive Y mouse movement is **down** the screen.
		//
		int deltaX = x - previousX;
		int deltaY = y - previousY;

		if ( deltaX > UNUSUAL_XDELTA || deltaX < -UNUSUAL_XDELTA ||
			deltaY > UNUSUAL_YDELTA || deltaY < -UNUSUAL_YDELTA )
		{
			// Deltas are too huge to be believable.  Probably a glitch.
			// Don't record the new XY location, or do anything.
			return;
		}

		double xRotationAngle = deltaY * XRotationFactor;
		double yRotationAngle = deltaX * YRotationFactor;

		//
		// Build transforms
		//
		transform1.rotX( xRotationAngle );
		transform2.rotY( yRotationAngle );

		// Get and save the current transform matrix
		subjectTransformGroup.getTransform( currentTransform );
		currentTransform.get( matrix );
		translate.set( matrix.m03, matrix.m13, matrix.m23 );

		// Translate to the origin, rotate, then translate back
		currentTransform.setTranslation( origin );
		currentTransform.mul( transform1, currentTransform );
		currentTransform.mul( transform2, currentTransform );
		currentTransform.setTranslation( translate );

		// Update the transform group
		subjectTransformGroup.setTransform( currentTransform );

		previousX = x;
		previousY = y;
	}


	/**
	 * Respond to a button2 event (press, release, or drag).
	 *
	 * @param mouseEvent A MouseEvent to respond to.
	 */
	public void onButton2( MouseEvent mev )
	{
		if ( subjectTransformGroup == null )
			return;

		int x = mev.getX( );
		int y = mev.getY( );

		if ( mev.getID( ) == MouseEvent.MOUSE_PRESSED )
		{
			// Mouse button pressed:  record position
			previousX = x;
			previousY = y;

			// Change to a "move" cursor
			if ( parentComponent != null )
			{
				savedCursor = parentComponent.getCursor( );
				parentComponent.setCursor(
					Cursor.getPredefinedCursor( Cursor.MOVE_CURSOR ) );
			}
			return;
		}
		if ( mev.getID( ) == MouseEvent.MOUSE_RELEASED )
		{
			// Mouse button released:  do nothing

			// Switch the cursor back
			if ( parentComponent != null )
				parentComponent.setCursor( savedCursor );
			return;
		}

		//
		// Mouse moved while button down:  create a translation
		//
		// Compute the delta in Y from the previous
		// position.  Use the delta to compute translation
		// distances with the mapping:
		//
		//   positive Y mouse delta --> positive Y-axis translation
		//
		// where positive X mouse movement is to the right, and
		// positive Y mouse movement is **down** the screen.
		//
		int deltaY = y - previousY;

		if ( deltaY > UNUSUAL_YDELTA || deltaY < -UNUSUAL_YDELTA )
		{
			// Deltas are too huge to be believable.  Probably a glitch.
			// Don't record the new XY location, or do anything.
			return;
		}

		double zTranslationDistance = deltaY * ZTranslationFactor;

		//
		// Build transforms
		//
		translate.set( 0.0, 0.0, zTranslationDistance );
		transform1.set( translate );

		// Get and save the current transform
		subjectTransformGroup.getTransform( currentTransform );

		// Translate as needed
		currentTransform.mul( transform1, currentTransform );

		// Update the transform group
		subjectTransformGroup.setTransform( currentTransform );

		previousX = x;
		previousY = y;
	}


	/**
	 * Respond to a button3 event (press, release, or drag).
	 *
	 * @param mouseEvent A MouseEvent to respond to.
	 */
	public void onButton3( MouseEvent mev )
	{
		if ( subjectTransformGroup == null )
			return;

		int x = mev.getX( );
		int y = mev.getY( );

		if ( mev.getID( ) == MouseEvent.MOUSE_PRESSED )
		{
			// Mouse button pressed:  record position
			previousX = x;
			previousY = y;

			// Change to a "move" cursor
			if ( parentComponent != null )
			{
				savedCursor = parentComponent.getCursor( );
				parentComponent.setCursor(
					Cursor.getPredefinedCursor( Cursor.MOVE_CURSOR ) );
			}
			return;
		}
		if ( mev.getID( ) == MouseEvent.MOUSE_RELEASED )
		{
			// Mouse button released:  do nothing

			// Switch the cursor back
			if ( parentComponent != null )
				parentComponent.setCursor( savedCursor );
			return;
		}

		//
		// Mouse moved while button down:  create a translation
		//
		// Compute the delta in X and Y from the previous
		// position.  Use the delta to compute translation
		// distances with the mapping:
		//
		//   positive X mouse delta --> positive X-axis translation
		//   positive Y mouse delta --> negative Y-axis translation
		//
		// where positive X mouse movement is to the right, and
		// positive Y mouse movement is **down** the screen.
		//
		int deltaX = x - previousX;
		int deltaY = y - previousY;

		if ( deltaX > UNUSUAL_XDELTA || deltaX < -UNUSUAL_XDELTA ||
			deltaY > UNUSUAL_YDELTA || deltaY < -UNUSUAL_YDELTA )
		{
			// Deltas are too huge to be believable.  Probably a glitch.
			// Don't record the new XY location, or do anything.
			return;
		}

		double xTranslationDistance = deltaX * XTranslationFactor;
		double yTranslationDistance = -deltaY * YTranslationFactor;

		//
		// Build transforms
		//
		translate.set( xTranslationDistance, yTranslationDistance, 0.0 );
		transform1.set( translate );

		// Get and save the current transform
		subjectTransformGroup.getTransform( currentTransform );

		// Translate as needed
		currentTransform.mul( transform1, currentTransform );

		// Update the transform group
		subjectTransformGroup.setTransform( currentTransform );

		previousX = x;
		previousY = y;
	}


	/**
	 * Respond to an elapsed frames event (assuming subclass has set up a
	 * wakeup criterion for it).
	 *
	 * @param time A WakeupOnElapsedFrames criterion to respond to.
	 */
	public void onElapsedFrames( WakeupOnElapsedFrames timeEvent )
	{
		// Can't happen
	}
}