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| 1 | +/* |
| 2 | + * Copyright (c) 2009-2022 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 | +package com.jme3.util; |
| 33 | + |
| 34 | +import com.jme3.bounding.BoundingBox; |
| 35 | +import com.jme3.bounding.BoundingSphere; |
| 36 | +import com.jme3.bounding.BoundingVolume; |
| 37 | +import com.jme3.math.FastMath; |
| 38 | + |
| 39 | +/** |
| 40 | + * <code>AreaUtils</code> is used to calculate the area of various objects, such as bounding volumes. These |
| 41 | + * functions are very loose approximations. |
| 42 | + * |
| 43 | + * @author Joshua Slack |
| 44 | + * @version $Id: AreaUtils.java 4131 2009-03-19 20:15:28Z blaine.dev $ |
| 45 | + */ |
| 46 | +public final class AreaUtils { |
| 47 | + /** |
| 48 | + * A private constructor to inhibit instantiation of this class. |
| 49 | + */ |
| 50 | + private AreaUtils() { |
| 51 | + } |
| 52 | + |
| 53 | + /** |
| 54 | + * Estimate the screen area of a bounding volume. If the volume isn't a |
| 55 | + * BoundingSphere, BoundingBox, or OrientedBoundingBox, 0 is returned. |
| 56 | + * |
| 57 | + * @param bound The bounds to calculate the volume from. |
| 58 | + * @param distance The distance from camera to object. |
| 59 | + * @param screenWidth The width of the screen. |
| 60 | + * @return The area in pixels on the screen of the bounding volume. |
| 61 | + */ |
| 62 | + public static float calcScreenArea(BoundingVolume bound, float distance, float screenWidth) { |
| 63 | + if (bound.getType() == BoundingVolume.Type.Sphere) { |
| 64 | + return calcScreenArea((BoundingSphere) bound, distance, screenWidth); |
| 65 | + } else if (bound.getType() == BoundingVolume.Type.AABB) { |
| 66 | + return calcScreenArea((BoundingBox) bound, distance, screenWidth); |
| 67 | + } |
| 68 | + return 0.0f; |
| 69 | + } |
| 70 | + |
| 71 | + private static float calcScreenArea(BoundingSphere bound, float distance, float screenWidth) { |
| 72 | + // Where is the center point and a radius point that lies in a plan parallel to the view plane? |
| 73 | + // // Calc radius based on these two points and plug into circle area formula. |
| 74 | + // Vector2f centerSP = null; |
| 75 | + // Vector2f outerSP = null; |
| 76 | + // float radiusSq = centerSP.subtract(outerSP).lengthSquared(); |
| 77 | + float radius = (bound.getRadius() * screenWidth) / (distance * 2); |
| 78 | + return radius * radius * FastMath.PI; |
| 79 | + } |
| 80 | + |
| 81 | + private static float calcScreenArea(BoundingBox bound, float distance, float screenWidth) { |
| 82 | + // Calc as if we are a BoundingSphere for now... |
| 83 | + float radiusSquare = bound.getXExtent() * bound.getXExtent() |
| 84 | + + bound.getYExtent() * bound.getYExtent() |
| 85 | + + bound.getZExtent() * bound.getZExtent(); |
| 86 | + return ((radiusSquare * screenWidth * screenWidth) / (distance * distance * 4)) * FastMath.PI; |
| 87 | + } |
| 88 | +} |
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