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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.replica.replicaisland;
     18 
     19 /**
     20  * An Axis-Aligned rectangular collision volume.  This code treats other volumes as if they are
     21  * also rectangles when calculating intersections.  Therefore certain types of intersections, such
     22  * as sphere vs rectangle, may not be absolutely precise (in the case of a sphere vs a rectangle,
     23  * for example, a new rectangle that fits the sphere is used to perform the intersection test, so
     24  * there is some potential for false-positives at the corners).  However, for our purposes absolute
     25  * precision isn't necessary, so this simple implementation is sufficient.
     26  */
     27 public class AABoxCollisionVolume extends CollisionVolume {
     28     private Vector2 mWidthHeight;
     29     private Vector2 mBottomLeft;
     30 
     31     public AABoxCollisionVolume(float offsetX, float offsetY, float width, float height) {
     32         super();
     33         mBottomLeft = new Vector2(offsetX, offsetY);
     34         mWidthHeight = new Vector2(width, height);
     35     }
     36 
     37     public AABoxCollisionVolume(float offsetX, float offsetY, float width, float height,
     38             int hit) {
     39         super(hit);
     40         mBottomLeft = new Vector2(offsetX, offsetY);
     41         mWidthHeight = new Vector2(width, height);
     42     }
     43 
     44     @Override
     45     public final float getMaxX() {
     46         return mBottomLeft.x + mWidthHeight.x;
     47     }
     48 
     49     @Override
     50     public final float getMinX() {
     51         return mBottomLeft.x;
     52     }
     53 
     54     @Override
     55     public final float getMaxY() {
     56         return mBottomLeft.y + mWidthHeight.y;
     57     }
     58 
     59     @Override
     60     public final float getMinY() {
     61         return mBottomLeft.y;
     62     }
     63 
     64     /**
     65      * Calculates the intersection of this volume and another, and returns true if the
     66      * volumes intersect.  This test treats the other volume as an AABox.
     67      * @param position The world position of this volume.
     68      * @param other The volume to test for intersections.
     69      * @param otherPosition The world position of the other volume.
     70      * @return true if the volumes overlap, false otherwise.
     71      */
     72     @Override
     73     public boolean intersects(Vector2 position, FlipInfo flip, CollisionVolume other,
     74             Vector2 otherPosition, FlipInfo otherFlip) {
     75         final float left = getMinXPosition(flip) + position.x;
     76         final float right = getMaxXPosition(flip) + position.x;
     77         final float bottom = getMinYPosition(flip) + position.y;
     78         final float top = getMaxYPosition(flip) + position.y;
     79 
     80         final float otherLeft = other.getMinXPosition(otherFlip) + otherPosition.x;
     81         final float otherRight = other.getMaxXPosition(otherFlip) + otherPosition.x;
     82         final float otherBottom = other.getMinYPosition(otherFlip) + otherPosition.y;
     83         final float otherTop = other.getMaxYPosition(otherFlip) + otherPosition.y;
     84 
     85         final boolean result = boxIntersect(left, right, top, bottom,
     86                     otherLeft, otherRight, otherTop, otherBottom)
     87                 || boxIntersect(otherLeft, otherRight, otherTop, otherBottom,
     88                     left, right, top, bottom);
     89 
     90         return result;
     91     }
     92 
     93     /** Tests two axis-aligned boxes for overlap. */
     94     private boolean boxIntersect(float left1, float right1, float top1, float bottom1,
     95             float left2, float right2, float top2, float bottom2) {
     96         final boolean horizontalIntersection = left1 < right2 && left2 < right1;
     97         final boolean verticalIntersection = top1 > bottom2 && top2 > bottom1;
     98         final boolean intersecting = horizontalIntersection && verticalIntersection;
     99         return intersecting;
    100     }
    101 
    102     /** Increases the size of this volume as necessary to fit the passed volume. */
    103     public void growBy(CollisionVolume other) {
    104         final float maxX;
    105         final float minX;
    106 
    107         final float maxY;
    108         final float minY;
    109 
    110         if (mWidthHeight.length2() > 0) {
    111             maxX = Math.max(getMaxX(), other.getMaxX());
    112             minX = Math.max(getMinX(), other.getMinX());
    113             maxY = Math.max(getMaxY(), other.getMaxY());
    114             minY = Math.max(getMinY(), other.getMinY());
    115         } else {
    116             maxX = other.getMaxX();
    117             minX = other.getMinX();
    118             maxY = other.getMaxY();
    119             minY = other.getMinY();
    120         }
    121         final float horizontalDelta = maxX - minX;
    122         final float verticalDelta = maxY - minY;
    123         mBottomLeft.set(minX, minY);
    124         mWidthHeight.set(horizontalDelta, verticalDelta);
    125     }
    126 
    127 }
    128