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      1 /*
      2  * Copyright (c) 2009-2010 jMonkeyEngine
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are
      7  * met:
      8  *
      9  * * Redistributions of source code must retain the above copyright
     10  *   notice, this list of conditions and the following disclaimer.
     11  *
     12  * * Redistributions in binary form must reproduce the above copyright
     13  *   notice, this list of conditions and the following disclaimer in the
     14  *   documentation and/or other materials provided with the distribution.
     15  *
     16  * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
     17  *   may be used to endorse or promote products derived from this software
     18  *   without specific prior written permission.
     19  *
     20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     21  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     22  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     23  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
     24  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     25  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     26  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     27  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
     28  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
     29  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     30  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 package com.jme3.scene.control;
     34 
     35 import com.jme3.bounding.BoundingBox;
     36 import com.jme3.bounding.BoundingSphere;
     37 import com.jme3.bounding.BoundingVolume;
     38 import com.jme3.math.FastMath;
     39 
     40 /**
     41  * <code>AreaUtils</code> is used to calculate the area of various objects, such as bounding volumes.  These
     42  * functions are very loose approximations.
     43  * @author Joshua Slack
     44  * @version $Id: AreaUtils.java 4131 2009-03-19 20:15:28Z blaine.dev $
     45  */
     46 
     47 public class AreaUtils {
     48 
     49   /**
     50    * calcScreenArea -- in Pixels
     51    * Aproximates the screen area of a bounding volume.  If the volume isn't a
     52    * BoundingSphere, BoundingBox, or OrientedBoundingBox 0 is returned.
     53    *
     54    * @param bound The bounds to calculate the volume from.
     55    * @param distance The distance from camera to object.
     56    * @param screenWidth The width of the screen.
     57    * @return The area in pixels on the screen of the bounding volume.
     58    */
     59   public static float calcScreenArea(BoundingVolume bound, float distance, float screenWidth) {
     60       if (bound.getType() == BoundingVolume.Type.Sphere){
     61           return calcScreenArea((BoundingSphere) bound, distance, screenWidth);
     62       }else if (bound.getType() == BoundingVolume.Type.AABB){
     63           return calcScreenArea((BoundingBox) bound, distance, screenWidth);
     64       }
     65       return 0.0f;
     66   }
     67 
     68   private static float calcScreenArea(BoundingSphere bound, float distance, float screenWidth) {
     69     // Where is the center point and a radius point that lies in a plan parallel to the view plane?
     70 //    // Calc radius based on these two points and plug into circle area formula.
     71 //    Vector2f centerSP = null;
     72 //    Vector2f outerSP = null;
     73 //    float radiusSq = centerSP.subtract(outerSP).lengthSquared();
     74       float radius = (bound.getRadius() * screenWidth) / (distance * 2);
     75       return radius * radius * FastMath.PI;
     76   }
     77 
     78   private static float calcScreenArea(BoundingBox bound, float distance, float screenWidth) {
     79       // Calc as if we are a BoundingSphere for now...
     80       float radiusSquare = bound.getXExtent() * bound.getXExtent()
     81                          + bound.getYExtent() * bound.getYExtent()
     82                          + bound.getZExtent() * bound.getZExtent();
     83       return ((radiusSquare * screenWidth * screenWidth) / (distance * distance * 4)) * FastMath.PI;
     84   }
     85 }