Android游戏框架之基础之AA碰撞系统

浏览数：20 / 时间：2015年06月11日

AA 碰撞体就是将所有的物体设置为矩形框进行碰撞计算。下面是代码

Java代码

/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.replica.replicaisland;
/**
* An Axis-Aligned rectangular collision volume. This code treats other volumes as if they are
* also rectangles when calculating intersections. Therefore certain types of intersections, such
* as sphere vs rectangle, may not be absolutely precise (in the case of a sphere vs a rectangle,
* for example, a new rectangle that fits the sphere is used to perform the intersection test, so
* there is some potential for false-positives at the corners). However, for our purposes absolute
* precision isn‘t necessary, so this simple implementation is sufficient.
*/
public class AABoxCollisionVolume extends CollisionVolume {
private Vector2 mWidthHeight;
private Vector2 mBottomLeft;
public AABoxCollisionVolume(float offsetX, float offsetY, float width, float height) {
super();
mBottomLeft = new Vector2(offsetX, offsetY);
mWidthHeight = new Vector2(width, height);
}
public AABoxCollisionVolume(float offsetX, float offsetY, float width, float height,
int hit) {
super(hit);
mBottomLeft = new Vector2(offsetX, offsetY);
mWidthHeight = new Vector2(width, height);
}
@Override
public final float getMaxX() {
return mBottomLeft.x + mWidthHeight.x;
}
@Override
public final float getMinX() {
return mBottomLeft.x;
}
@Override
public final float getMaxY() {
return mBottomLeft.y + mWidthHeight.y;
}
@Override
public final float getMinY() {
return mBottomLeft.y;
}
/**
* Calculates the intersection of this volume and another, and returns true if the
* volumes intersect. This test treats the other volume as an AABox.
* @param position The world position of this volume.
* @param other The volume to test for intersections.
* @param otherPosition The world position of the other volume.
* @return true if the volumes overlap, false otherwise.
*/
@Override
public boolean intersects(Vector2 position, FlipInfo flip, CollisionVolume other,
Vector2 otherPosition, FlipInfo otherFlip) {
final float left = getMinXPosition(flip) + position.x;
final float right = getMaxXPosition(flip) + position.x;
final float bottom = getMinYPosition(flip) + position.y;
final float top = getMaxYPosition(flip) + position.y;
final float otherLeft = other.getMinXPosition(otherFlip) + otherPosition.x;
final float otherRight = other.getMaxXPosition(otherFlip) + otherPosition.x;
final float otherBottom = other.getMinYPosition(otherFlip) + otherPosition.y;
final float otherTop = other.getMaxYPosition(otherFlip) + otherPosition.y;
final boolean result = boxIntersect(left, right, top, bottom,
otherLeft, otherRight, otherTop, otherBottom)
|| boxIntersect(otherLeft, otherRight, otherTop, otherBottom,
left, right, top, bottom);
return result;
}
/** Tests two axis-aligned boxes for overlap. */
private boolean boxIntersect(float left1, float right1, float top1, float bottom1,
float left2, float right2, float top2, float bottom2) {
final boolean horizontalIntersection = left1 < right2 && left2 < right1;
final boolean verticalIntersection = top1 > bottom2 && top2 > bottom1;
final boolean intersecting = horizontalIntersection && verticalIntersection;
return intersecting;
}
/** Increases the size of this volume as necessary to fit the passed volume. */
public void growBy(CollisionVolume other) {
final float maxX;
final float minX;
final float maxY;
final float minY;
if (mWidthHeight.length2() > 0) {
maxX = Math.max(getMaxX(), other.getMaxX());
minX = Math.max(getMinX(), other.getMinX());
maxY = Math.max(getMaxY(), other.getMaxY());
minY = Math.max(getMinY(), other.getMinY());
} else {
maxX = other.getMaxX();
minX = other.getMinX();
maxY = other.getMaxY();
minY = other.getMinY();
}
final float horizontalDelta = maxX - minX;
final float verticalDelta = maxY - minY;
mBottomLeft.set(minX, minY);
mWidthHeight.set(horizontalDelta, verticalDelta);
}
}