Billboard.java

/**
 * Copyright (c) 2003-2009, Xith3D Project Group all rights reserved.
 * 
 * Portions based on the Java3D interface, Copyright by Sun Microsystems.
 * Many thanks to the developers of Java3D and Sun Microsystems for their
 * innovation and design.
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package org.xith3d.scenegraph;

import org.openmali.types.twodee.Sized2iRO;
import org.openmali.vecmath2.Matrix3f;

/**
 * A BillBoard is someting, that always faces the View.
 * Implement this interface in Shape3D extensions to make the renderer use it.
 * 
 * @author Marvin Froehlich (aka Qudus)
 */
public interface Billboard
{
    /**
     * Returns the Billboard desired on screen dimensions. 
     * 
     * For the default Billboard implementation,
     * this method should return {@code null}, as the on-screen dimension is dependant on the 
     * distance between the Billboard and the camera.
     * 
     * If the desired effect is a Billboard having a constant size on screen (usefull for icons, 
     * or textual information that should be readable at any distance), then this method should
     * return the desired size in pixels. In this case, the {@code Sized2iRO} returned will
     * generally be a constant.
     * 
     * This method is called by the renderer each frame the Billboard is rendered.
     * 
     * Note to implementers: for this behaviour to work properly, the unmodified geometry 
     * should of course have a unit size, ie: the width and the height should should be 
     * equal to 1f. Else the effective desired size on screen will be scaled accordingly.
     * 
     * @return the desired size on screen, or {@code null} for a standard billboard.
     */
    public Sized2iRO getSizeOnScreen();
    
    /**
     * This method is called by the renderer each frame, the BillBoard is
     * rendered.
     * 
     * @param viewRotation the camera's rotation
     * @param frameId the current rendered frame's id
     * @param nanoTime
     * @param nanoStep
     */
    public void updateFaceToCamera( Matrix3f viewRotation, long frameId, long nanoTime, long nanoStep );
}