org.andengine.util.algorithm.collision.BaseCollisionChecker Maven / Gradle / Ivy
package org.andengine.util.algorithm.collision;
/**
* (c) 2010 Nicolas Gramlich
* (c) 2011 Zynga Inc.
*
* @author Nicolas Gramlich
* @since 11:50:19 - 11.03.2010
*/
public class BaseCollisionChecker {
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// Constants
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// Fields
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// Constructors
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// Getter & Setter
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// Methods for/from SuperClass/Interfaces
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// Methods
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public static boolean checkAxisAlignedRectangleCollision(final float pLeftA, final float pTopA, final float pRightA, final float pBottomA, final float pLeftB, final float pTopB, final float pRightB, final float pBottomB) {
return pLeftA < pRightB &&
pLeftB < pRightA &&
pTopA < pBottomB &&
pTopB < pBottomA;
}
public static boolean checkAxisAlignedRectangleContains(final float pLeft, final float pTop, final float pRight, final float pBottom, final float pX, final float pY) {
return pX > pLeft &&
pX < pRight &&
pY > pTop &&
pY < pBottom;
}
/**
* Returns an indicator of where the specified point (PX, PY) lies with
* respect to the line segment from (X1, Y1) to (X2, Y2). The
* return value can be either 1, -1, or 0 and indicates in which direction
* the specified line must pivot around its first endpoint, (X1, Y1),
* in order to point at the specified point (PX, PY).
*
* A return value of 1 indicates that the line segment must turn in the
* direction that takes the positive X axis towards the negative Y axis. In
* the default coordinate system used by Java 2D, this direction is
* counterclockwise.
*
* A return value of -1 indicates that the line segment must turn in the
* direction that takes the positive X axis towards the positive Y axis. In
* the default coordinate system, this direction is clockwise.
*
* A return value of 0 indicates that the point lies exactly on the line
* segment. Note that an indicator value of 0 is rare and not useful for
* determining colinearity because of floating point rounding issues.
*
* If the point is colinear with the line segment, but not between the
* endpoints, then the value will be -1 if the point lies
* "beyond (X1, Y1)" or 1 if the point lies "beyond (X2, Y2)".
*
* @param pX1
* , Y1 the coordinates of the beginning of the specified
* line segment
* @param pX2
* , Y2 the coordinates of the end of the specified line
* segment
* @param pPX
* , PY the coordinates of the specified point to be
* compared with the specified line segment
* @return an integer that indicates the position of the third specified
* coordinates with respect to the line segment formed by the first
* two specified coordinates.
*/
public static int relativeCCW(final float pX1, final float pY1, float pX2, float pY2, float pPX, float pPY) {
pX2 -= pX1;
pY2 -= pY1;
pPX -= pX1;
pPY -= pY1;
float ccw = pPX * pY2 - pPY * pX2;
if (ccw == 0.0f) {
// The point is colinear, classify based on which side of
// the segment the point falls on. We can calculate a
// relative value using the projection of PX,PY onto the
// segment - a negative value indicates the point projects
// outside of the segment in the direction of the particular
// endpoint used as the origin for the projection.
ccw = pPX * pX2 + pPY * pY2;
if (ccw > 0.0f) {
// Reverse the projection to be relative to the original X2,Y2
// X2 and Y2 are simply negated.
// PX and PY need to have (X2 - X1) or (Y2 - Y1) subtracted
// from them (based on the original values)
// Since we really want to get a positive answer when the
// point is "beyond (X2,Y2)", then we want to calculate
// the inverse anyway - thus we leave X2 & Y2 negated.
pPX -= pX2;
pPY -= pY2;
ccw = pPX * pX2 + pPY * pY2;
if (ccw < 0.0f) {
ccw = 0.0f;
}
}
}
return (ccw < 0.0f) ? -1 : ((ccw > 0.0f) ? 1 : 0);
}
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// Inner and Anonymous Classes
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}