[u/mrichter/AliRoot.git] / GEANT321 / ggeom / gingtr.F

*
* $Id$
*
* $Log$
* Revision 1.1.1.1  1995/10/24 10:20:50  cernlib
* Geant
*
*
#include "geant321/pilot.h"
*CMZ :  3.21/02 29/03/94  15.41.29  by  S.Giani
*-- Author :
      SUBROUTINE GINGTR(X,P,IYES)
C.
C.    ******************************************************************
C.    *                                                                *
C.    *                                                                *
C.    *          SUBROUTINE GINGTR(X,P,IYES)                           *
C.    *      Routine performes GINME type function to determine        *
C.    *      whether the point X is in the GTRA shape with parameters  *
C.    *      P. IYES is returned 1 if it is 0 if not.                  *
C.    *          A.C.McPherson 22nd April 1985                         *
C.    *                                                                *
C.    *      Called by : GINME                                         *
C.    *                                                                *
C     ******************************************************************
C.
      DIMENSION X(3),P(30),XPT(4),YPT(4)
C.
C.            ----------------------------------------
C.
C             First the range in Z is checked.
C
      IYES=0
      IF(ABS(X(3)).GT.P(1)) GO TO 30
C
C             Next the four corners at the z of the input point (X(3))
C             are computed as:
C
      DO 10 I=1,4
      I0=I*4+11
      XPT(I) = P(I0)+P(I0+2)*X(3)
      YPT(I) = P(I0+1)+P(I0+3)*X(3)
   10 CONTINUE
C
C             Then the cross product between the vector from that
C             corner to the input point and the vector from that corner
C             to the next corner is computed and its sign is
C             interrogated. Since the quadralateral is convex, if any
C             one of these signs is wrong, the point is outside the
C             shape. This task is performed as follows:
C
      DO 20 I=1,4
      J = I+1
      IF(J.EQ.5) J=1
      CROSS = (X(1)-XPT(I))*(YPT(J)-YPT(I)) -
     +        (X(2)-YPT(I))*(XPT(J)-XPT(I))
      IF(CROSS.GT.0.0) GO TO 30
   20 CONTINUE
      IYES = 1
   30 CONTINUE
      RETURN
      END
Commit	Line	Data
fe4da5cc	1	*
	2	* $Id$
	3	*
	4	* $Log$
	5	* Revision 1.1.1.1 1995/10/24 10:20:50 cernlib
	6	* Geant
	7	*
	8	*
	9	#include "geant321/pilot.h"
	10	*CMZ : 3.21/02 29/03/94 15.41.29 by S.Giani
	11	*-- Author :
	12	SUBROUTINE GINGTR(X,P,IYES)
	13	C.
	14	C. ******************************************************************
	15	C. * *
	16	C. * *
	17	C. * SUBROUTINE GINGTR(X,P,IYES) *
	18	C. * Routine performes GINME type function to determine *
	19	C. * whether the point X is in the GTRA shape with parameters *
	20	C. * P. IYES is returned 1 if it is 0 if not. *
	21	C. * A.C.McPherson 22nd April 1985 *
	22	C. * *
	23	C. * Called by : GINME *
	24	C. * *
	25	C ******************************************************************
	26	C.
	27	DIMENSION X(3),P(30),XPT(4),YPT(4)
	28	C.
	29	C. ----------------------------------------
	30	C.
	31	C First the range in Z is checked.
	32	C
	33	IYES=0
	34	IF(ABS(X(3)).GT.P(1)) GO TO 30
	35	C
	36	C Next the four corners at the z of the input point (X(3))
	37	C are computed as:
	38	C
	39	DO 10 I=1,4
	40	I0=I*4+11
	41	XPT(I) = P(I0)+P(I0+2)*X(3)
	42	YPT(I) = P(I0+1)+P(I0+3)*X(3)
	43	10 CONTINUE
	44	C
	45	C Then the cross product between the vector from that
	46	C corner to the input point and the vector from that corner
	47	C to the next corner is computed and its sign is
	48	C interrogated. Since the quadralateral is convex, if any
	49	C one of these signs is wrong, the point is outside the
	50	C shape. This task is performed as follows:
	51	C
	52	DO 20 I=1,4
	53	J = I+1
	54	IF(J.EQ.5) J=1
	55	CROSS = (X(1)-XPT(I))*(YPT(J)-YPT(I)) -
	56	+ (X(2)-YPT(I))*(XPT(J)-XPT(I))
	57	IF(CROSS.GT.0.0) GO TO 30
	58	20 CONTINUE
	59	IYES = 1
	60	30 CONTINUE
	61	RETURN
	62	END