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
33package com.jme3.scene.control;
34
35import com.jme3.bounding.BoundingBox;
36import com.jme3.bounding.BoundingSphere;
37import com.jme3.bounding.BoundingVolume;
38import 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
47public 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}