billboard.java

JAVA3D矩陈的相关类

/*
 * $RCSfile: Billboard.java,v $
 *
 * Copyright (c) 2007 Sun Microsystems, Inc. All rights reserved.
 *
 * Use is subject to license terms.
 *
 * $Revision: 1.5 $
 * $Date: 2007/02/09 17:17:52 $
 * $State: Exp $
 */

package javax.media.j3d;

import java.util.Enumeration;
import javax.vecmath.Point3f;
import javax.vecmath.Point3d;
import javax.vecmath.Vector3d;
import javax.vecmath.Vector3f;
import javax.vecmath.AxisAngle4d;

/**
 * The Billboard behavior node operates on the TransformGroup node
 * to cause the local +z axis of the TransformGroup to point at
 * the viewer's eye position. This is done  regardless of the transforms 
 * above the specified TransformGroup  node in the scene graph.
 *
 * <p>
 * If the alignment mode is ROTATE_ABOUT_AXIS, the rotation will be
 * around the specified axis.  If the alignment mode is
 * ROTATE_ABOUT_POINT, the rotation will be about the specified
 * point, with an additional rotation to align the +y axis of the
 * TransformGroup with the +y axis in the View.
 *
 * <p>
 * Note that in a multiple View system, the alignment is done to
 * the primary View only.
 *
 * <p>
 * Billboard nodes are ideal for drawing screen aligned-text or
 * for drawing roughly-symmetrical objects.  A typical use might
 * consist of a quadrilateral that contains a texture of a tree.
 *
 * @see OrientedShape3D
 */
public class Billboard extends Behavior {
    /**
     * Specifies that rotation should be about the specified axis.
     */
    public static final int ROTATE_ABOUT_AXIS          = 0;

    /**
     * Specifies that rotation should be about the specified point and
     * that the children's Y-axis should match the view object's Y-axis.
     */
    public static final int ROTATE_ABOUT_POINT         = 1;

    // Wakeup condition for Billboard node
    WakeupOnElapsedFrames wakeupFrame = new WakeupOnElapsedFrames(0, true);


    // Specifies the billboard's mode of operation. One of ROTATE_AXIAL,
    // ROTATE_POINT_VIEW, or ROTATE_POINT_WORLD.
    int mode = ROTATE_ABOUT_AXIS;

    // Axis about which to rotate.
    Vector3f axis = new Vector3f(0.0f, 1.0f, 0.0f);
    Point3f rotationPoint = new Point3f(0.0f, 0.0f, 1.0f);
    private Vector3d nAxis = new Vector3d(0.0, 1.0, 0.0); // normalized axis

    // TransformGroup to operate on.
    TransformGroup tg = null;


    // reused temporaries
    private Point3d viewPosition = new Point3d();
    private Point3d yUpPoint = new Point3d();

    private Vector3d eyeVec = new Vector3d(); 
    private Vector3d yUp = new Vector3d();
    private Vector3d zAxis  = new Vector3d();
    private Vector3d yAxis  = new Vector3d();
    private Vector3d vector = new Vector3d();

    private AxisAngle4d aa = new AxisAngle4d();

    static final double EPSILON = 1.0e-6;

    /**
     * Constructs a Billboard node with default parameters.
     * The default values are as follows:
     * <ul>
     * alignment mode : ROTATE_ABOUT_AXIS<br>
     * alignment axis : Y-axis (0,1,0)<br>
     * rotation point : (0,0,1)<br>
     * target transform group: null<br>
     *</ul>
     */
    public Billboard() {
        nAxis.x = 0.0;
        nAxis.y = 1.0;
        nAxis.z = 0.0;
    }


    /**
     * Constructs a Billboard node with default parameters that operates
     * on the specified TransformGroup node.
     * The default alignment mode is ROTATE_ABOUT_AXIS rotation with the axis
     * pointing along the Y axis.
     * @param tg the TransformGroup node that this Billboard
     * node operates upon
     */
    public Billboard(TransformGroup tg) {
	this.tg = tg;
        nAxis.x = 0.0;
        nAxis.y = 1.0;
        nAxis.z = 0.0;

    }


    /**
     * Constructs a Billboard node with the specified axis and mode
     * that operates on the specified TransformGroup node.
     * The specified axis must not be parallel to the <i>Z</i>
     * axis--(0,0,<i>z</i>) for any value of <i>z</i>.  It is not
     * possible for the +<i>Z</i> axis to point at the viewer's eye
     * position by rotating about itself.  The target transform will
     * be set to the identity if the axis is (0,0,<i>z</i>).
     *
     * @param tg the TransformGroup node that this Billboard
     * node operates upon
     * @param mode alignment mode, one of ROTATE_ABOUT_AXIS or 
     * ROTATE_ABOUT_POINT
     * @param axis the ray about which the billboard rotates
     */
    public Billboard(TransformGroup tg, int mode, Vector3f axis) {
	this.tg = tg;
	this.mode = mode;
	this.axis.set(axis);
        double invMag;
        invMag =  1.0/Math.sqrt(axis.x*axis.x + axis.y*axis.y + axis.z*axis.z);
        nAxis.x = (double)axis.x*invMag;
        nAxis.y = (double)axis.y*invMag;
        nAxis.z = (double)axis.z*invMag;

    }

    /**
     * Constructs a Billboard node with the specified rotation point and mode
     * that operates on the specified TransformGroup node.
     * @param tg the TransformGroup node that this Billboard
     * node operates upon
     * @param mode alignment mode, one of ROTATE_ABOUT_AXIS or 
     * ROTATE_ABOUT_POINT
     * @param point the position about which the billboard rotates
     */
    public Billboard(TransformGroup tg, int mode, Point3f point) {
	this.tg = tg;
	this.mode = mode;
	this.rotationPoint.set(point);
    }

    /**
     * Sets the alignment mode.
     * @param mode one of: ROTATE_ABOUT_AXIS or ROTATE_ABOUT_POINT
     */
    public void setAlignmentMode(int mode) {
	this.mode = mode;
    }


    /**
     * Gets the alignment mode.
     * @return one of: ROTATE_ABOUT_AXIS or ROTATE_ABOUT_POINT
     */
    public int getAlignmentMode() {
	return this.mode;
    }


    /**
     * Sets the alignment axis.
     * The specified axis must not be parallel to the <i>Z</i>
     * axis--(0,0,<i>z</i>) for any value of <i>z</i>.  It is not
     * possible for the +<i>Z</i> axis to point at the viewer's eye
     * position by rotating about itself.  The target transform will
     * be set to the identity if the axis is (0,0,<i>z</i>).
     *
     * @param axis the ray about which the billboard rotates
     */
    public void setAlignmentAxis(Vector3f axis) {
	this.axis.set(axis);
        double invMag;
        invMag =  1.0/Math.sqrt(axis.x*axis.x + axis.y*axis.y + axis.z*axis.z);
        nAxis.x = (double)axis.x*invMag;
        nAxis.y = (double)axis.y*invMag;
        nAxis.z = (double)axis.z*invMag;

    }


    /**
     * Sets the alignment axis.
     * The specified axis must not be parallel to the <i>Z</i>
     * axis--(0,0,<i>z</i>) for any value of <i>z</i>.  It is not
     * possible for the +<i>Z</i> axis to point at the viewer's eye
     * position by rotating about itself.  The target transform will
     * be set to the identity if the axis is (0,0,<i>z</i>).
     *
     * @param x the x component of the ray about which the billboard rotates
     * @param y the y component of the ray about which the billboard rotates
     * @param z the z component of the ray about which the billboard rotates
     */
    public void setAlignmentAxis(float x, float y, float z) {
	this.axis.set(x, y, z);
        this.axis.set(axis);
        double invMag;
        invMag =  1.0/Math.sqrt(axis.x*axis.x + axis.y*axis.y + axis.z*axis.z);
        nAxis.x = (double)axis.x*invMag;
        nAxis.y = (double)axis.y*invMag;
        nAxis.z = (double)axis.z*invMag;

    }


    /**
     * Gets the alignment axis and sets the parameter to this value.
     * @param axis the vector that will contain the ray about which
     * the billboard rotates
     */
    public void getAlignmentAxis(Vector3f axis)  {
	axis.set(this.axis);
    }

    /**
     * Sets the rotation point.
     * @param point the point about which the billboard rotates
     */
    public void setRotationPoint(Point3f point) {
	this.rotationPoint.set(point);
    }


    /**
     * Sets the rotation point.
     * @param x the x component of the point about which the billboard rotates
     * @param y the y component of the point about which the billboard rotates
     * @param z the z component of the point about which the billboard rotates
     */
    public void setRotationPoint(float x, float y, float z) {
	this.rotationPoint.set(x, y, z);
    }


    /**
     * Gets the rotation point and sets the parameter to this value.
     * @param point the position the Billboard rotates about
     */
    public void getRotationPoint(Point3f point)  {
	point.set(this.rotationPoint);
    }
  /**
     * Sets the tranformGroup for this Billboard object.
     * @param tg the transformGroup node which replaces the current
     * transformGroup node for this Billboard
     */  
    public void setTarget(TransformGroup tg ) {
        this.tg = tg;
    }

    /**
      *  Returns a copy of the transformGroup associated with this Billboard.
      *  @return the TranformGroup for this Billboard 
      */ 
    public TransformGroup getTarget() {
          return(tg);
    }


    /**
     * Initialize method that sets up initial wakeup criteria.
     */
    public void initialize() {
	// Insert wakeup condition into queue
	wakeupOn(wakeupFrame);
    }


    /**
     * Process stimulus method that computes appropriate transform.
     * @param criteria an enumeration of the criteria that caused the
     * stimulus
     */
    public void processStimulus(Enumeration criteria) {
        double angle = 0.0;
        double mag,sign;
	double tx,ty,tz;

        if( tg == null ){
	   wakeupOn(wakeupFrame);
	   return;
        }
 
	//  get viewplatforms's location in virutal world
	View v = this.getView();
	if( v == null ) {
	    wakeupOn(wakeupFrame);
 	    return;
        }
        Canvas3D canvas = (Canvas3D)v.getCanvas3D(0);
	boolean status;

	Transform3D xform = new Transform3D();
	Transform3D bbXform = new Transform3D();
	Transform3D prevTransform = new Transform3D();

	((TransformGroupRetained) tg.retained).getTransform(prevTransform);

        if (mode == ROTATE_ABOUT_AXIS ) {   // rotate about axis
	    canvas.getCenterEyeInImagePlate(viewPosition);
	    canvas.getImagePlateToVworld(xform); // xform is imagePlateToLocal
	    xform.transform(viewPosition);

	    // get billboard's transform

	    // since we are using getTransform() to get the transform
	    // of the transformGroup, we need to use getLocalToVworld()