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*DECK NXTPRR
FUNCTION NXTPRR(XYREC1,XYREC2,XYRECI)
*
*----------
*
*Purpose:
* Find the rectangle representing the intersection of two rectangles.
*
*Copyright:
* Copyright (C) 2005 Ecole Polytechnique de Montreal
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
*Author(s): G. Marleau.
*
*Parameters: input
* XYREC1 spatial description of the first rectangle with:
* XYREC1(1) for left face; XYREC1(2) for right face;
* XYREC1(3) for bottom face; XYREC1(4) for top face
* positions.
* XYREC2 spatial description of the second rectangle with:
* XYREC2(1) for left face; XYREC2(2) for right face;
* XYREC2(3) for bottom face; XYREC2(4) for top face
* positions.
*Parameters: output
* NXTPRR type of intersection between rectangles where
* =0 means that there is no intersection
* between the two regions;
* =1 means that there is an intersection between
* between the two regions.
* XYRECI spatial description of the intersection rectangle with:
* XYRECI(1) for left face; XYRECI(2) for right face;
* XYRECI(3) for bottom face; XYRECI(4) for top face
* positions.
*
*Reference:
* G. Marleau,
* New Geometries Processing in DRAGON: The NXT: Module,
* Report IGE-260, Polytechnique Montreal,
* Montreal, 2005.
*
*----------
*
IMPLICIT NONE
*----
* Subroutine arguments
*----
INTEGER NXTPRR
DOUBLE PRECISION XYREC1(4),XYREC2(4)
DOUBLE PRECISION XYRECI(4)
*----
* Local parameters
*----
INTEGER IOUT
CHARACTER NAMSBR*6
PARAMETER (IOUT=6,NAMSBR='NXTPRR')
*----
* Local variables
*----
INTEGER IFACE
*----
* Find position of surface of intersection
* -> for left and bottom faces, maximum $X$ and $Y$ location.
* -> for right and top faces, minimum $X$ and $Y$ location.
*----
NXTPRR=1
DO 100 IFACE=1,3,2
XYRECI(IFACE)=MAX(XYREC2(IFACE),XYREC1(IFACE))
100 CONTINUE
DO 101 IFACE=2,4,2
XYRECI(IFACE)=MIN(XYREC2(IFACE),XYREC1(IFACE))
101 CONTINUE
*----
* Test if intersection is valid
*----
IF(XYRECI(1) .GE. XYRECI(2) .OR.
> XYRECI(3) .GE. XYRECI(4)) NXTPRR=0
RETURN
END
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