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 }
