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

*
* $Id$
*
* $Log$
* Revision 1.1.1.1  1995/10/24 10:20:53  cernlib
* Geant
*
*
#include "geant321/pilot.h"
*CMZ :  3.21/02 29/03/94  15.41.29  by  S.Giani
*-- Author :
      SUBROUTINE GNOSPH (X, PAR, IACT, SNEXT, SNXT, SAFE)
C.
C.    ******************************************************************
C.    *                                                                *
C.    *       COMPUTE DISTANCE UP TO INTERSECTION WITH 'SPHE' VOLUME,  *
C.    *       FROM OUTSIDE POINT X(1-3) ALONG DIRECTION X(4-6)SPHERE   *
C.    *                                                                *
C.    *       PAR   (input)  : volume parameters                       *
C.    *       IACT  (input)  : action flag                             *
C.    *         = 0  Compute SAFE only                                 *
C.    *         = 1  Compute SAFE, and SNXT only if SNEXT .GT.new SAFE *
C.    *         = 2  Compute both SAFE and SNXT                        *
C.    *         = 3  Compute SNXT only                                 *
C.    *       SNEXT (input)  : see IACT = 1                            *
C.    *       SNXT  (output) : distance to volume boundary             *
C.    *       SAFE  (output) : shortest distance to any boundary       *
C.    *                                                                *
C.    *    ==>Called by : GNEXT, GTNEXT                                *
C.    *         Author  A.McPherson,  P.Weidhaas  *********            *
C.    *                                                                *
C.    ******************************************************************
C.
#if !defined(CERNLIB_SINGLE)
      IMPLICIT DOUBLE PRECISION (A-H,O-Z)
#endif
#include "geant321/gconsp.inc"
      REAL X(6),PAR(6),SNEXT,SNXT,SAFE
      DIMENSION IS(4),SS(4)
C.
C.    ----------------------------------------------------------------
C.
 
      SNXT = BIG
      R2  = X(1)*X(1) + X(2)*X(2) + X(3)*X(3)
      R   = SQRT (R2)
 
      IF (IACT .LT. 3) THEN
 
C       -------------------------------------------------
C       |  Compute safety-distance 'SAFE' (P.Weidhaas)  |
C       -------------------------------------------------
 
        RIN  = PAR(1)
        ROUT = PAR(2)
        IF (R .LT. RIN) THEN
          SAFE  = RIN - R
        ELSEIF (R .GT. ROUT) THEN
          SAFE  = R - ROUT
        ENDIF
 
 
        IF (IACT .EQ. 0) GO TO 999
        IF (IACT .EQ. 1) THEN
          IF (SNEXT .LT. SAFE) GO TO 999
        ENDIF
      ENDIF
 
 
C     ------------------------------------------------
C     |  Compute vector-distance 'SNXT' (McPherson)  |
C     ------------------------------------------------
 
 
      BA=X(1)*X(4)+X(2)*X(5)+X(3)*X(6)
      IF(R2.GE.PAR(2)*PAR(2).AND.BA.GE.0.0) GO TO 999
C
      CA=R2-PAR(2)*PAR(2)
      DISC=BA*BA-CA
      IF(DISC.LE.0.0) GO TO 999
C
      RDISC=SQRT(DISC)
      SMAX=-BA+RDISC
      SMIN=-BA-RDISC
C
C                   NOW DO RMIN
C
      CA=R2-PAR(1)*PAR(1)
      DISC=BA*BA-CA
C
      SMIN1=SMIN
      SMAX1=-1.0
      SMIN2=SMIN
      SMAX2=SMAX
C
      IF(DISC.LE.0.0) GO TO 30
      RDISC=SQRT(DISC)
      SMIN2=-BA+RDISC
      SMAX1=-BA-RDISC
C
   30 CONTINUE
C
C                   NOW DO THE PHI STUFF.
C
      IP2=0
      SMNP1=0.0
      SMXP1=SMAX2
C
      IF(PAR(6)-PAR(5).GE.360.0) GO TO  110
C
      DPSGN=X(1)*X(5)-X(2)*X(4)
      PHL=PAR(5)/RADDEG
      PHH=PAR(6)/RADDEG
      ISMIN=0
      ISMAX=0
C
      TSGN=SIN(PHL)
      TCSG=COS(PHL)
      DEN=X(4)*TSGN-X(5)*TCSG
      IF(DEN.EQ.0.0) GO TO 40
      SNL=(X(2)*TCSG-X(1)*TSGN)/DEN
      IF(ABS(TSGN).GT.1.E-6.AND.(X(2)+SNL*X(5))*TSGN.LT.0.) GO TO 40
      IF(ABS(TCSG).GT.1.E-6.AND.(X(1)+SNL*X(4))*TCSG.LT.0.) GO TO 40
C
      ISMIN=1
      SMIN=SNL
      IF(DPSGN.GT.0.0) GO TO 40
      ISMIN=0
      ISMAX=1
      SMAX=SNL
C
   40 CONTINUE
C
      TSGN=SIN(PHH)
      TCSG=COS(PHH)
      DEN=X(4)*TSGN-X(5)*TCSG
      IF(DEN.EQ.0.0) GO TO 60
      SNH=(X(2)*TCSG-X(1)*TSGN)/DEN
      IF(ABS(TSGN).GT.1.E-6.AND.(X(2)+SNH*X(5))*TSGN.LT.0.) GO TO 60
      IF(ABS(TCSG).GT.1.E-6.AND.(X(1)+SNH*X(4))*TCSG.LT.0.) GO TO 60
      IF(DPSGN.LT.0.0) GO TO 50
      ISMAX=1
      SMAX=SNH
      GO TO 60
C
   50 CONTINUE
      ISMIN=1
      SMIN=SNH
C
   60 CONTINUE
C
      IF(ISMIN.EQ.0.OR.ISMAX.EQ.0) GO TO 80
      IF(SMAX.LT.0.0.AND.SMAX.GT.SMIN) GO TO 999
      IF(SMIN.LT.0.0) SMIN=0.0
      IF(SMAX.LT.0.0) GO TO  100
      IF(SMAX.GT.SMIN) GO TO 70
C
C                         SMAX +VE AND LESS THAN SMIN - 2 ALLOWED
C                         REGIONS.
C
      IP2=1
      SMXP1=SMAX
      SMNP2=SMIN
      SMXP2=SMAX2
      GO TO  110
C
   70 CONTINUE
C
C                         SMIN +VE AND SMAX GT SMIN: NORMAL SINGLE
C                         REGION
C
      SMNP1=SMIN
      SMXP1=SMAX
      GO TO  110
C
   80 CONTINUE
      IF(ISMIN.EQ.1) GO TO  100
      IF(ISMAX.EQ.0) GO TO  90
C
C                    SMAX BUT NO SMIN
C
      SMXP1=SMAX
      GO TO  110
C
   90 CONTINUE
C
C                   NO SMIN OR SMAX: ALWAYS IN OR ALWAYS OUT.
C
      DPH=PAR(5)-PAR(4)
      IF(DPH.LT.180.0.AND.DPH.GT.0.0) GO TO 999
      IF(DPH.LT.-180.0) GO TO 999
      GO TO  110
C
  100 CONTINUE
C
C                  SMIN BUT NO SMAX.
C
      SMNP1=SMIN
C
  110 CONTINUE
C
C                  NOW DO THETA.
C
      IT2=0
      SMNT1=0.0
      SMXT1=SMAX2
      IF(PAR(4)-PAR(3).GE.180.0) GO TO 360
C
      TH=PAR(3)
      IT=1
      ITLN=0
      ITLX=0
      ITHN=0
      ITHX=0
C
  120 CONTINUE
C
      IF(TH.NE.90.0) GO TO 130
      IF(X(6).EQ.0.0) GO TO 220
C
      ST=-X(3)/X(6)
      STST=-X(6)
      GO TO 180
C
  130 CONTINUE
C
      TT=TAN(TH/RADDEG)
      TT2=TT*TT
C
      A=X(4)*X(4)+X(5)*X(5)-TT2*X(6)*X(6)
      B=X(1)*X(4)+X(2)*X(5)-TT2*X(3)*X(6)
      C=X(1)*X(1)+X(2)*X(2)-TT2*X(3)*X(3)
C
      IF(A.NE.0.0) GO TO 140
      IF(B.EQ.0.0) GO TO 220
C
      ST=-C*0.5/B
C
      Z=X(3)+ST*X(6)
      IF(Z*TT.LT.0.0) GO TO 220
C
      STST=(B+ST*A)/Z
      ITRY=2
C
      GO TO 180
  140 CONTINUE
C
      BA=B/A
      CA=C/A
      DISC=BA*BA-CA
      IF(DISC.LT.0.0) GO TO 220
C
      RDISC=0.0
      IF(DISC.GT.0.0) RDISC=SQRT(DISC)
      ITRY=1
      ST=-BA-RDISC
C
  150 CONTINUE
C
      IF(ST.LT.0.0) GO TO 160
      Z=X(3)+ST*X(6)
      IF(Z.EQ.0.0.AND.ABS(A).LT.0.0) GO TO 170
      IF(RDISC.EQ.0.0) GO TO 160
      IF(Z*TT.LT.0.0) GO TO 160
C
      STST=(B+ST*A)/Z
      GO TO 180
C
  160 CONTINUE
C
      IF(ITRY.EQ.2) GO TO 220
      ST=-BA+RDISC
      ITRY=2
      GO TO 150
C
  170 CONTINUE
      STST=-X(6)
  180 CONTINUE
C
      IF(IT.NE.1) GO TO 200
      IF(STST.GT.0.0) GO TO 190
      ITLX=1
      SMXTL=ST
      GO TO 160
C
  190 CONTINUE
      ITLN=1
      SMNTL=ST
      GO TO 160
C
  200 CONTINUE
      IF(STST.GT.0.0) GO TO 210
      ITHN=1
      SMNTH=ST
      GO TO 160
C
  210 CONTINUE
      ITHX=1
      SMXTH=ST
      GO TO 160
C
  220 CONTINUE
      IF(IT.EQ.2) GO TO 230
      IT=2
      TH=PAR(4)
      GO TO 120
C
  230 CONTINUE
C
C              ORDER THE VARIOUS BOUNDARIES.
C
      ICOUNT=0
      IF(ITLN.EQ.0.OR.SMNTL.LE.0.0) GO TO 240
      IS(1)=1
      SS(1)=SMNTL
      ICOUNT=1
C
  240 CONTINUE
      IF(ITLX.EQ.0.OR.SMXTL.LE.0.0) GO TO 260
      IPL=ICOUNT+1
      IF(ICOUNT.EQ.0.OR.SMXTL.GT.SS(1)) GO TO 250
      IS(2)=IS(1)
      SS(2)=SS(1)
      IPL=1
  250 CONTINUE
      ICOUNT=ICOUNT+1
      IS(IPL)=2
      SS(IPL)=SMXTL
C
  260 CONTINUE
      IST=3
      IF(ITHN.EQ.0.OR.SMNTH.LE.0.0) GO TO 320
      STEST=SMNTH
C
  270 CONTINUE
      IPL=ICOUNT+1
      IF(ICOUNT.EQ.0) GO TO 310
      DO 280 IC=1,ICOUNT
      IC1=ICOUNT-IC+1
      IF(STEST.GT.SS(IC1)) GO TO 290
      IPL=IPL-1
  280 CONTINUE
C
  290 CONTINUE
      IF(IPL.EQ.ICOUNT+1) GO TO 310
      IM=ICOUNT+1-IPL
      DO 300 I=1,IM
      I1=ICOUNT-I+1
      I2=I1+1
      IS(I2)=IS(I1)
      SS(I2)=SS(I1)
  300 CONTINUE
C
  310 CONTINUE
      ICOUNT=ICOUNT+1
      IS(IPL)=IST
      SS(IPL)=STEST
C
  320 CONTINUE
      IF(IST.EQ.4) GO TO 330
      IF(ITHX.EQ.0.OR.SMXTH.LE.0.0) GO TO 330
      IST=4
      STEST=SMXTH
      GO TO 270
C
  330 CONTINUE
C
C               CHECK WHETHER 1ST IS MAX OR MIN.
C
      IF(ICOUNT.EQ.0) GO TO 350
      IF(IS(1).EQ.2.OR.IS(1).EQ.4) GO TO 340
C
C               START WITH MIN.
C
      SMNT1=SS(1)
      IF(ICOUNT.GE.2) SMXT1=SS(2)
      IF(ICOUNT.LE.2) GO TO 360
      IT2=1
      SMNT2=SS(3)
      SMXT2=SMAX2
      IF(ICOUNT.GE.4) SMXT2=SS(4)
      GO TO 360
C
  340 CONTINUE
C
C              START WITH MAX SO 1ST MIN IS 0.0
C
      SMNT1=0.0
      SMXT1=SS(1)
      IF(ICOUNT.LE.1) GO TO 360
      IT2=1
      SMNT2=SS(2)
      SMXT2=SMAX2
      IF(ICOUNT.GE.3) SMXT2=SS(3)
      GO TO 360
C
  350 CONTINUE
C
C              NO INTERSECTIONS ALWAYS IN OR ALWAYS OUT.
C
      R=X(1)*X(1)+X(2)*X(2)
      IF(R.GT.0.0) R=SQRT(R)
      TH=90.0
      IF(X(3).NE.0.0) TH=ATAN(R/X(3))*RADDEG
      IF(TH.LT.0.0) TH=180.0+TH
      IF(TH.LT.PAR(3).OR.TH.GT.PAR(4)) GO TO 999
C
  360 CONTINUE
C
C              NOW FIND SMALLEST S ALOWED BY ALL.
C
      IF(SMAX1.LE.SMIN1) GO TO 370
      SMAXR=SMAX1
      SMINR=SMIN1
      IRT=1
      GO TO 380
C
  370 CONTINUE
      SMAXR=SMAX2
      SMINR=SMIN2
      IRT=2
C
  380 CONTINUE
      IF(SMNP1.GT.SMAXR) GO TO 430
      IF(SMXP1.LT.SMINR) GO TO 390
      SMIN=SMINR
      SMAX=SMAXR
      IF(SMNP1.GT.SMIN) SMIN=SMNP1
      IF(SMXP1.LT.SMAX) SMAX=SMXP1
      IPT=1
      GO TO 400
C
  390 CONTINUE
      IF(IP2.EQ.0) GO TO 430
      IF(SMNP2.GT.SMAXR) GO TO 430
      IF(SMXP2.LT.SMINR) GO TO 430
      SMIN=SMINR
      SMAX=SMAXR
      IF(SMNP2.GT.SMIN) SMIN=SMNP2
      IF(SMXP2.LT.SMAX) SMAX=SMXP2
      IPT=2
C
  400 CONTINUE
C
      IF(SMNT1.GT.SMAX) GO TO 420
      IF(SMXT1.LT.SMIN) GO TO 410
      IF(SMNT1.GT.SMIN) SMIN=SMNT1
      GO TO 440
C
  410 CONTINUE
      IF(IT2.EQ.0) GO TO 420
      IF(SMNT2.GT.SMAX) GO TO 420
      IF(SMXT2.LT.SMIN) GO TO 420
      IF(SMNT2.GT.SMIN) SMIN=SMNT2
      GO TO 440
C
  420 CONTINUE
      IF(IPT.EQ.1) GO TO 390
  430 CONTINUE
      IF(IRT.EQ.1) GO TO 370
      GO TO 999
C
  440 CONTINUE
      IF(SMIN.LE.0.)GO TO 999
      SNXT = SMIN
 
  999 CONTINUE
      END
Commit	Line	Data
fe4da5cc	1	*
	2	* $Id$
	3	*
	4	* $Log$
	5	* Revision 1.1.1.1 1995/10/24 10:20:53 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 GNOSPH (X, PAR, IACT, SNEXT, SNXT, SAFE)
	13	C.
	14	C. ******************************************************************
	15	C. * *
	16	C. * COMPUTE DISTANCE UP TO INTERSECTION WITH 'SPHE' VOLUME, *
	17	C. * FROM OUTSIDE POINT X(1-3) ALONG DIRECTION X(4-6)SPHERE *
	18	C. * *
	19	C. * PAR (input) : volume parameters *
	20	C. * IACT (input) : action flag *
	21	C. * = 0 Compute SAFE only *
	22	C. * = 1 Compute SAFE, and SNXT only if SNEXT .GT.new SAFE *
	23	C. * = 2 Compute both SAFE and SNXT *
	24	C. * = 3 Compute SNXT only *
	25	C. * SNEXT (input) : see IACT = 1 *
	26	C. * SNXT (output) : distance to volume boundary *
	27	C. * SAFE (output) : shortest distance to any boundary *
	28	C. * *
	29	C. * ==>Called by : GNEXT, GTNEXT *
	30	C. * Author A.McPherson, P.Weidhaas ********* *
	31	C. * *
	32	C. ******************************************************************
	33	C.
	34	#if !defined(CERNLIB_SINGLE)
	35	IMPLICIT DOUBLE PRECISION (A-H,O-Z)
	36	#endif
	37	#include "geant321/gconsp.inc"
	38	REAL X(6),PAR(6),SNEXT,SNXT,SAFE
	39	DIMENSION IS(4),SS(4)
	40	C.
	41	C. ----------------------------------------------------------------
	42	C.
	43
	44	SNXT = BIG
	45	R2 = X(1)X(1) + X(2)X(2) + X(3)*X(3)
	46	R = SQRT (R2)
	47
	48	IF (IACT .LT. 3) THEN
	49
	50	C -------------------------------------------------
	51	C \| Compute safety-distance 'SAFE' (P.Weidhaas) \|
	52	C -------------------------------------------------
	53
	54	RIN = PAR(1)
	55	ROUT = PAR(2)
	56	IF (R .LT. RIN) THEN
	57	SAFE = RIN - R
	58	ELSEIF (R .GT. ROUT) THEN
	59	SAFE = R - ROUT
	60	ENDIF
	61
	62
	63	IF (IACT .EQ. 0) GO TO 999
	64	IF (IACT .EQ. 1) THEN
65	IF (SNEXT .LT. SAFE) GO TO 999
66	ENDIF
67	ENDIF
68
69
70	C ------------------------------------------------
71	C \| Compute vector-distance 'SNXT' (McPherson) \|
72	C ------------------------------------------------
73
74
75	BA=X(1)X(4)+X(2)X(5)+X(3)*X(6)
76	IF(R2.GE.PAR(2)*PAR(2).AND.BA.GE.0.0) GO TO 999
77	C
78	CA=R2-PAR(2)*PAR(2)
79	DISC=BA*BA-CA
80	IF(DISC.LE.0.0) GO TO 999
81	C
82	RDISC=SQRT(DISC)
83	SMAX=-BA+RDISC
84	SMIN=-BA-RDISC
85	C
86	C NOW DO RMIN
87	C
88	CA=R2-PAR(1)*PAR(1)
89	DISC=BA*BA-CA
90	C
91	SMIN1=SMIN
92	SMAX1=-1.0
93	SMIN2=SMIN
94	SMAX2=SMAX
95	C
96	IF(DISC.LE.0.0) GO TO 30
97	RDISC=SQRT(DISC)
98	SMIN2=-BA+RDISC
99	SMAX1=-BA-RDISC
100	C
101	30 CONTINUE
102	C
103	C NOW DO THE PHI STUFF.
104	C
105	IP2=0
106	SMNP1=0.0
107	SMXP1=SMAX2
108	C
109	IF(PAR(6)-PAR(5).GE.360.0) GO TO 110
110	C
111	DPSGN=X(1)X(5)-X(2)X(4)
112	PHL=PAR(5)/RADDEG
113	PHH=PAR(6)/RADDEG
114	ISMIN=0
115	ISMAX=0
116	C
117	TSGN=SIN(PHL)
118	TCSG=COS(PHL)
119	DEN=X(4)TSGN-X(5)TCSG
120	IF(DEN.EQ.0.0) GO TO 40
121	SNL=(X(2)TCSG-X(1)TSGN)/DEN
122	IF(ABS(TSGN).GT.1.E-6.AND.(X(2)+SNLX(5))TSGN.LT.0.) GO TO 40
123	IF(ABS(TCSG).GT.1.E-6.AND.(X(1)+SNLX(4))TCSG.LT.0.) GO TO 40
124	C
125	ISMIN=1
126	SMIN=SNL
127	IF(DPSGN.GT.0.0) GO TO 40
128	ISMIN=0
129	ISMAX=1
130	SMAX=SNL
131	C
132	40 CONTINUE
133	C
134	TSGN=SIN(PHH)
135	TCSG=COS(PHH)
136	DEN=X(4)TSGN-X(5)TCSG
137	IF(DEN.EQ.0.0) GO TO 60
138	SNH=(X(2)TCSG-X(1)TSGN)/DEN
139	IF(ABS(TSGN).GT.1.E-6.AND.(X(2)+SNHX(5))TSGN.LT.0.) GO TO 60
140	IF(ABS(TCSG).GT.1.E-6.AND.(X(1)+SNHX(4))TCSG.LT.0.) GO TO 60
141	IF(DPSGN.LT.0.0) GO TO 50
142	ISMAX=1
143	SMAX=SNH
144	GO TO 60
145	C
146	50 CONTINUE
147	ISMIN=1
148	SMIN=SNH
149	C
150	60 CONTINUE
151	C
152	IF(ISMIN.EQ.0.OR.ISMAX.EQ.0) GO TO 80
153	IF(SMAX.LT.0.0.AND.SMAX.GT.SMIN) GO TO 999
154	IF(SMIN.LT.0.0) SMIN=0.0
155	IF(SMAX.LT.0.0) GO TO 100
156	IF(SMAX.GT.SMIN) GO TO 70
157	C
158	C SMAX +VE AND LESS THAN SMIN - 2 ALLOWED
159	C REGIONS.
160	C
161	IP2=1
162	SMXP1=SMAX
163	SMNP2=SMIN
164	SMXP2=SMAX2
165	GO TO 110
166	C
167	70 CONTINUE
168	C
169	C SMIN +VE AND SMAX GT SMIN: NORMAL SINGLE
170	C REGION
171	C
172	SMNP1=SMIN
173	SMXP1=SMAX
174	GO TO 110
175	C
176	80 CONTINUE
177	IF(ISMIN.EQ.1) GO TO 100
178	IF(ISMAX.EQ.0) GO TO 90
179	C
180	C SMAX BUT NO SMIN
181	C
182	SMXP1=SMAX
183	GO TO 110
184	C
185	90 CONTINUE
186	C
187	C NO SMIN OR SMAX: ALWAYS IN OR ALWAYS OUT.
188	C
189	DPH=PAR(5)-PAR(4)
190	IF(DPH.LT.180.0.AND.DPH.GT.0.0) GO TO 999
191	IF(DPH.LT.-180.0) GO TO 999
192	GO TO 110
193	C
194	100 CONTINUE
195	C
196	C SMIN BUT NO SMAX.
197	C
198	SMNP1=SMIN
199	C
200	110 CONTINUE
201	C
202	C NOW DO THETA.
203	C
204	IT2=0
205	SMNT1=0.0
206	SMXT1=SMAX2
207	IF(PAR(4)-PAR(3).GE.180.0) GO TO 360
208	C
209	TH=PAR(3)
210	IT=1
211	ITLN=0
212	ITLX=0
213	ITHN=0
214	ITHX=0
215	C
216	120 CONTINUE
217	C
218	IF(TH.NE.90.0) GO TO 130
219	IF(X(6).EQ.0.0) GO TO 220
220	C
221	ST=-X(3)/X(6)
222	STST=-X(6)
223	GO TO 180
224	C
225	130 CONTINUE
226	C
227	TT=TAN(TH/RADDEG)
228	TT2=TT*TT
229	C
230	A=X(4)X(4)+X(5)X(5)-TT2X(6)X(6)
231	B=X(1)X(4)+X(2)X(5)-TT2X(3)X(6)
232	C=X(1)X(1)+X(2)X(2)-TT2X(3)X(3)
233	C
234	IF(A.NE.0.0) GO TO 140
235	IF(B.EQ.0.0) GO TO 220
236	C
237	ST=-C*0.5/B
238	C
239	Z=X(3)+ST*X(6)
240	IF(Z*TT.LT.0.0) GO TO 220
241	C
242	STST=(B+ST*A)/Z
243	ITRY=2
244	C
245	GO TO 180
246	140 CONTINUE
247	C
248	BA=B/A
249	CA=C/A
250	DISC=BA*BA-CA
251	IF(DISC.LT.0.0) GO TO 220
252	C
253	RDISC=0.0
254	IF(DISC.GT.0.0) RDISC=SQRT(DISC)
255	ITRY=1
256	ST=-BA-RDISC
257	C
258	150 CONTINUE
259	C
260	IF(ST.LT.0.0) GO TO 160
261	Z=X(3)+ST*X(6)
262	IF(Z.EQ.0.0.AND.ABS(A).LT.0.0) GO TO 170
263	IF(RDISC.EQ.0.0) GO TO 160
264	IF(Z*TT.LT.0.0) GO TO 160
265	C
266	STST=(B+ST*A)/Z
267	GO TO 180
268	C
269	160 CONTINUE
270	C
271	IF(ITRY.EQ.2) GO TO 220
272	ST=-BA+RDISC
273	ITRY=2
274	GO TO 150
275	C
276	170 CONTINUE
277	STST=-X(6)
278	180 CONTINUE
279	C
280	IF(IT.NE.1) GO TO 200
281	IF(STST.GT.0.0) GO TO 190
282	ITLX=1
283	SMXTL=ST
284	GO TO 160
285	C
286	190 CONTINUE
287	ITLN=1
288	SMNTL=ST
289	GO TO 160
290	C
291	200 CONTINUE
292	IF(STST.GT.0.0) GO TO 210
293	ITHN=1
294	SMNTH=ST
295	GO TO 160
296	C
297	210 CONTINUE
298	ITHX=1
299	SMXTH=ST
300	GO TO 160
301	C
302	220 CONTINUE
303	IF(IT.EQ.2) GO TO 230
304	IT=2
305	TH=PAR(4)
306	GO TO 120
307	C
308	230 CONTINUE
309	C
310	C ORDER THE VARIOUS BOUNDARIES.
311	C
312	ICOUNT=0
313	IF(ITLN.EQ.0.OR.SMNTL.LE.0.0) GO TO 240
314	IS(1)=1
315	SS(1)=SMNTL
316	ICOUNT=1
317	C
318	240 CONTINUE
319	IF(ITLX.EQ.0.OR.SMXTL.LE.0.0) GO TO 260
320	IPL=ICOUNT+1
321	IF(ICOUNT.EQ.0.OR.SMXTL.GT.SS(1)) GO TO 250
322	IS(2)=IS(1)
323	SS(2)=SS(1)
324	IPL=1
325	250 CONTINUE
326	ICOUNT=ICOUNT+1
327	IS(IPL)=2
328	SS(IPL)=SMXTL
329	C
330	260 CONTINUE
331	IST=3
332	IF(ITHN.EQ.0.OR.SMNTH.LE.0.0) GO TO 320
333	STEST=SMNTH
334	C
335	270 CONTINUE
336	IPL=ICOUNT+1
337	IF(ICOUNT.EQ.0) GO TO 310
338	DO 280 IC=1,ICOUNT
339	IC1=ICOUNT-IC+1
340	IF(STEST.GT.SS(IC1)) GO TO 290
341	IPL=IPL-1
342	280 CONTINUE
343	C
344	290 CONTINUE
345	IF(IPL.EQ.ICOUNT+1) GO TO 310
346	IM=ICOUNT+1-IPL
347	DO 300 I=1,IM
348	I1=ICOUNT-I+1
349	I2=I1+1
350	IS(I2)=IS(I1)
351	SS(I2)=SS(I1)
352	300 CONTINUE
353	C
354	310 CONTINUE
355	ICOUNT=ICOUNT+1
356	IS(IPL)=IST
357	SS(IPL)=STEST
358	C
359	320 CONTINUE
360	IF(IST.EQ.4) GO TO 330
361	IF(ITHX.EQ.0.OR.SMXTH.LE.0.0) GO TO 330
362	IST=4
363	STEST=SMXTH
364	GO TO 270
365	C
366	330 CONTINUE
367	C
368	C CHECK WHETHER 1ST IS MAX OR MIN.
369	C
370	IF(ICOUNT.EQ.0) GO TO 350
371	IF(IS(1).EQ.2.OR.IS(1).EQ.4) GO TO 340
372	C
373	C START WITH MIN.
374	C
375	SMNT1=SS(1)
376	IF(ICOUNT.GE.2) SMXT1=SS(2)
377	IF(ICOUNT.LE.2) GO TO 360
378	IT2=1
379	SMNT2=SS(3)
380	SMXT2=SMAX2
381	IF(ICOUNT.GE.4) SMXT2=SS(4)
382	GO TO 360
383	C
384	340 CONTINUE
385	C
386	C START WITH MAX SO 1ST MIN IS 0.0
387	C
388	SMNT1=0.0
389	SMXT1=SS(1)
390	IF(ICOUNT.LE.1) GO TO 360
391	IT2=1
392	SMNT2=SS(2)
393	SMXT2=SMAX2
394	IF(ICOUNT.GE.3) SMXT2=SS(3)
395	GO TO 360
396	C
397	350 CONTINUE
398	C
399	C NO INTERSECTIONS ALWAYS IN OR ALWAYS OUT.
400	C
401	R=X(1)X(1)+X(2)X(2)
402	IF(R.GT.0.0) R=SQRT(R)
403	TH=90.0
404	IF(X(3).NE.0.0) TH=ATAN(R/X(3))*RADDEG
405	IF(TH.LT.0.0) TH=180.0+TH
406	IF(TH.LT.PAR(3).OR.TH.GT.PAR(4)) GO TO 999
407	C
408	360 CONTINUE
409	C
410	C NOW FIND SMALLEST S ALOWED BY ALL.
411	C
412	IF(SMAX1.LE.SMIN1) GO TO 370
413	SMAXR=SMAX1
414	SMINR=SMIN1
415	IRT=1
416	GO TO 380
417	C
418	370 CONTINUE
419	SMAXR=SMAX2
420	SMINR=SMIN2
421	IRT=2
422	C
423	380 CONTINUE
424	IF(SMNP1.GT.SMAXR) GO TO 430
425	IF(SMXP1.LT.SMINR) GO TO 390
426	SMIN=SMINR
427	SMAX=SMAXR
428	IF(SMNP1.GT.SMIN) SMIN=SMNP1
429	IF(SMXP1.LT.SMAX) SMAX=SMXP1
430	IPT=1
431	GO TO 400
432	C
433	390 CONTINUE
434	IF(IP2.EQ.0) GO TO 430
435	IF(SMNP2.GT.SMAXR) GO TO 430
436	IF(SMXP2.LT.SMINR) GO TO 430
437	SMIN=SMINR
438	SMAX=SMAXR
439	IF(SMNP2.GT.SMIN) SMIN=SMNP2
440	IF(SMXP2.LT.SMAX) SMAX=SMXP2
441	IPT=2
442	C
443	400 CONTINUE
444	C
445	IF(SMNT1.GT.SMAX) GO TO 420
446	IF(SMXT1.LT.SMIN) GO TO 410
447	IF(SMNT1.GT.SMIN) SMIN=SMNT1
448	GO TO 440
449	C
450	410 CONTINUE
451	IF(IT2.EQ.0) GO TO 420
452	IF(SMNT2.GT.SMAX) GO TO 420
453	IF(SMXT2.LT.SMIN) GO TO 420
454	IF(SMNT2.GT.SMIN) SMIN=SMNT2
455	GO TO 440
456	C
457	420 CONTINUE
458	IF(IPT.EQ.1) GO TO 390
459	430 CONTINUE
460	IF(IRT.EQ.1) GO TO 370
461	GO TO 999
462	C
463	440 CONTINUE
464	IF(SMIN.LE.0.)GO TO 999
465	SNXT = SMIN
466
467	999 CONTINUE
468	END