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

*
* $Id$
*
* $Log$
* Revision 1.1.1.1  1995/10/24 10:20:57  cernlib
* Geant
*
*
#include "geant321/pilot.h"
*CMZ :  3.21/02 29/03/94  15.41.31  by  S.Giani
*-- Author :
*
      SUBROUTINE GVLONG (DIR, C, NC, TAU, NTAU)
************************************************************************
*                                                                      *
* GVLONG calculates the distance to the surface along a      VP 920125 *
*        given DIRection                                               *
*                                                                      *
*        SHOULD BE called ONLY AFTER call GVSAFE.                      *
*        due to some results of GVSAFE are used.                       *
*        Just by this reason starting XYZ point                        *
*        is omitted                                                    *
*        =======================================                       *
*                                                                      *
* Input  : DIR -   direction                                           *
*          C   -   coeffs of surface (C(1) not used)                   *
*          NC  -   number of coefs                                     *
*                                                                      *
* Output : TAU -   TAU(1:2) distances to surface in increasing order   *
*                  in the units of the length of DIR                   *
*          NTAU -  number of distances (solutions)  (0,1,2)            *
*                                                                      *
************************************************************************
      COMMON /SLATE/ SLATE (40)
      INTEGER        ISLATE(40)
      EQUIVALENCE    (SLATE,ISLATE)
      REAL           C(*), DIR(3), TAU(2), CBA(3)
      LOGICAL        XLINE
*-----------------------------------------------------------------------
*
*     SLATE(10) is the value of S(X) = equation of the surface with
*     the point coordinates
*     SLATE(11),SLATE(12),SLATE(13) is the gradient to the surface
*
      NTAU = 0
      CBA(1) = SLATE(10)
      CBA(2) = SLATE(11)*DIR(1)+SLATE(12)*DIR(2)+SLATE(13)*DIR(3)
*
      CBA(3) = 0.
      XLINE  = .TRUE.
*
**              in case of a plane
      IF (NC.EQ.4)              GO TO 200
*
*     in case it is a simplified surface X=-C0,Y=-C0,Z=-C0, or X*2+Y*2=-C0
*
      IF (NC.EQ.2)              THEN
        IAX  = C(2)
        IF (IAX.NE.4)           GO TO 200
        CBA(3) = DIR(1)**2+DIR(2)**2
      ELSE
*
**              in case it is a surface with 7 or 10 coefficients
        CBA(3) = DIR(1)**2*C(5)+DIR(2)**2*C(6)+DIR(3)**2*C(7)
*
**              in case it is a surface with 10 coefficients
        IF (NC.EQ.10)           THEN
          CBA(3) = CBA(3) + C(08)*DIR(1)*DIR(2)
          CBA(3) = CBA(3) + C(09)*DIR(2)*DIR(3)
          CBA(3) = CBA(3) + C(10)*DIR(3)*DIR(1)
        ENDIF
      ENDIF
      XLINE = .FALSE.
*
  200 IF (XLINE)                THEN
*
*     in case it is a plane (4 coefficients) or a simplified surface
*
        IF (1.E+6*ABS(CBA(2)).LE.ABS(CBA(1)))   GO TO 999
        NTAU = 1
        TAU(1) = - CBA(1)/CBA(2)
      ELSE
*
**              in case it is a surface with 7 or 10 coefficients
        CALL GVPSQR (CBA, TAU, NTAU)
      ENDIF
*
  999 NTAU = MAX(0,NTAU)
      RETURN
      END
Commit	Line	Data
fe4da5cc	1	*
	2	* $Id$
	3	*
	4	* $Log$
	5	* Revision 1.1.1.1 1995/10/24 10:20:57 cernlib
	6	* Geant
	7	*
	8	*
	9	#include "geant321/pilot.h"
	10	*CMZ : 3.21/02 29/03/94 15.41.31 by S.Giani
	11	*-- Author :
	12	*
	13	SUBROUTINE GVLONG (DIR, C, NC, TAU, NTAU)
	14	************************************************************************
	15	* *
	16	* GVLONG calculates the distance to the surface along a VP 920125 *
	17	* given DIRection *
	18	* *
	19	* SHOULD BE called ONLY AFTER call GVSAFE. *
	20	* due to some results of GVSAFE are used. *
	21	* Just by this reason starting XYZ point *
	22	* is omitted *
	23	* ======================================= *
	24	* *
	25	* Input : DIR - direction *
	26	* C - coeffs of surface (C(1) not used) *
	27	* NC - number of coefs *
	28	* *
	29	* Output : TAU - TAU(1:2) distances to surface in increasing order *
	30	* in the units of the length of DIR *
	31	* NTAU - number of distances (solutions) (0,1,2) *
	32	* *
	33	************************************************************************
	34	COMMON /SLATE/ SLATE (40)
	35	INTEGER ISLATE(40)
	36	EQUIVALENCE (SLATE,ISLATE)
	37	REAL C(*), DIR(3), TAU(2), CBA(3)
	38	LOGICAL XLINE
	39	*-----------------------------------------------------------------------
	40	*
	41	* SLATE(10) is the value of S(X) = equation of the surface with
	42	* the point coordinates
	43	* SLATE(11),SLATE(12),SLATE(13) is the gradient to the surface
	44	*
	45	NTAU = 0
	46	CBA(1) = SLATE(10)
	47	CBA(2) = SLATE(11)DIR(1)+SLATE(12)DIR(2)+SLATE(13)*DIR(3)
	48	*
	49	CBA(3) = 0.
	50	XLINE = .TRUE.
	51	*
	52	** in case of a plane
	53	IF (NC.EQ.4) GO TO 200
	54	*
	55	* in case it is a simplified surface X=-C0,Y=-C0,Z=-C0, or X2+Y2=-C0
	56	*
	57	IF (NC.EQ.2) THEN
	58	IAX = C(2)
	59	IF (IAX.NE.4) GO TO 200
	60	CBA(3) = DIR(1)2+DIR(2)2
	61	ELSE
	62	*
	63	** in case it is a surface with 7 or 10 coefficients
	64	CBA(3) = DIR(1)*2C(5)+DIR(2)*2C(6)+DIR(3)*2C(7)
65	*
66	** in case it is a surface with 10 coefficients
67	IF (NC.EQ.10) THEN
68	CBA(3) = CBA(3) + C(08)DIR(1)DIR(2)
69	CBA(3) = CBA(3) + C(09)DIR(2)DIR(3)
70	CBA(3) = CBA(3) + C(10)DIR(3)DIR(1)
71	ENDIF
72	ENDIF
73	XLINE = .FALSE.
74	*
75	200 IF (XLINE) THEN
76	*
77	* in case it is a plane (4 coefficients) or a simplified surface
78	*
79	IF (1.E+6*ABS(CBA(2)).LE.ABS(CBA(1))) GO TO 999
80	NTAU = 1
81	TAU(1) = - CBA(1)/CBA(2)
82	ELSE
83	*
84	** in case it is a surface with 7 or 10 coefficients
85	CALL GVPSQR (CBA, TAU, NTAU)
86	ENDIF
87	*
88	999 NTAU = MAX(0,NTAU)
89	RETURN
90	END