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+/*
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+ * Copyright (c) 2009-2022 jMonkeyEngine
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+ * All rights reserved.
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+ *
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+ * Redistribution and use in source and binary forms, with or without
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+ * modification, are permitted provided that the following conditions are
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+ * met:
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+ *
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+ * * Redistributions of source code must retain the above copyright
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+ * notice, this list of conditions and the following disclaimer.
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+ *
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+ * * Redistributions in binary form must reproduce the above copyright
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+ * notice, this list of conditions and the following disclaimer in the
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+ * documentation and/or other materials provided with the distribution.
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+ *
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+ * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
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+ * may be used to endorse or promote products derived from this software
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+ * without specific prior written permission.
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+ *
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+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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+ */
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+package com.jme3.util;
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+
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+import com.jme3.bounding.BoundingBox;
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+import com.jme3.bounding.BoundingSphere;
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+import com.jme3.bounding.BoundingVolume;
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+import com.jme3.math.FastMath;
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+
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+/**
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+ * <code>AreaUtils</code> is used to calculate the area of various objects, such as bounding volumes. These
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+ * functions are very loose approximations.
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+ *
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+ * @author Joshua Slack
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+ * @version $Id: AreaUtils.java 4131 2009-03-19 20:15:28Z blaine.dev $
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+ */
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+public final class AreaUtils {
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+ /**
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+ * A private constructor to inhibit instantiation of this class.
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+ */
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+ private AreaUtils() {
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+ }
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+
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+ /**
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+ * Estimate the screen area of a bounding volume. If the volume isn't a
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+ * BoundingSphere, BoundingBox, or OrientedBoundingBox, 0 is returned.
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+ *
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+ * @param bound The bounds to calculate the volume from.
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+ * @param distance The distance from camera to object.
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+ * @param screenWidth The width of the screen.
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+ * @return The area in pixels on the screen of the bounding volume.
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+ */
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+ public static float calcScreenArea(BoundingVolume bound, float distance, float screenWidth) {
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+ if (bound.getType() == BoundingVolume.Type.Sphere) {
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+ return calcScreenArea((BoundingSphere) bound, distance, screenWidth);
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+ } else if (bound.getType() == BoundingVolume.Type.AABB) {
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+ return calcScreenArea((BoundingBox) bound, distance, screenWidth);
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+ }
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+ return 0.0f;
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+ }
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+
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+ private static float calcScreenArea(BoundingSphere bound, float distance, float screenWidth) {
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+ // Where is the center point and a radius point that lies in a plan parallel to the view plane?
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+ // // Calc radius based on these two points and plug into circle area formula.
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+ // Vector2f centerSP = null;
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+ // Vector2f outerSP = null;
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+ // float radiusSq = centerSP.subtract(outerSP).lengthSquared();
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+ float radius = (bound.getRadius() * screenWidth) / (distance * 2);
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+ return radius * radius * FastMath.PI;
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+ }
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+
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+ private static float calcScreenArea(BoundingBox bound, float distance, float screenWidth) {
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+ // Calc as if we are a BoundingSphere for now...
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+ float radiusSquare = bound.getXExtent() * bound.getXExtent()
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+ + bound.getYExtent() * bound.getYExtent()
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+ + bound.getZExtent() * bound.getZExtent();
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+ return ((radiusSquare * screenWidth * screenWidth) / (distance * distance * 4)) * FastMath.PI;
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+ }
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+}
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