This commit was generated by cvs2svn to compensate for changes in r2,

[u/mrichter/AliRoot.git] / GEANT321 / gphys / gfang.F

diff --git a/GEANT321/gphys/gfang.F b/GEANT321/gphys/gfang.F
new file mode 100644 (file)
index 0000000..ed8bfb4
--- /dev/null
+++ b/GEANT321/gphys/gfang.F
@@ -0,0 +1,68 @@
+*
+* $Id$
+*
+* $Log$
+* Revision 1.1.1.1  1995/10/24 10:21:24  cernlib
+* Geant
+*
+*
+#include "geant321/pilot.h"
+*CMZ :  3.21/02 06/07/94  18.28.55  by  S.Giani
+*-- Author :
+      SUBROUTINE GFANG(P,COSTH,SINTH,COSPH,SINPH,ROTATE)
+C.
+C.    ******************************************************************
+C.    *                                                                *
+C.    *  Finds theta-phi angles for a particle with director cosines P *
+C.    *  The logical flag ROTATE indicates whether the the director    *
+C.    *  cosines are along the Z axis (.FALSE.) or not (.TRUE.).       *
+C.    *                                                                *
+C.    *    ==>Called by :                                              *
+C.    *       Author    F.Carminati  *********                         *
+C.    *                                                                *
+C.    *                                                                *
+C.    ******************************************************************
+C.
+      DIMENSION P(*)
+#if !defined(CERNLIB_SINGLE)
+      DOUBLE PRECISION DUX, DUY, DUZ, DSITH2, ONE, DNORM
+#endif
+      LOGICAL ROTATE
+      PARAMETER (ONE=1)
+C.
+C.    ------------------------------------------------------------------
+C.
+      DUX      = P(1)
+      DUY      = P(2)
+      DUZ      = P(3)
+      ROTATE   = .TRUE.
+      IF(ABS(DUZ).GE.0.85) THEN
+         DSITH2=DUX**2+DUY**2
+         IF(DSITH2.GT.0.) THEN
+            COSTH  = SIGN(ONE,DUZ)*SQRT(ONE-DSITH2)
+            DSITH  = SQRT(DSITH2)
+            SINTH  = DSITH
+            COSPH  = DUX/DSITH
+            SINPH  = DUY/DSITH
+         ELSEIF(DUZ.GT.0.)THEN
+            ROTATE = .FALSE.
+            COSTH =  1.
+            SINTH =  0.
+            COSPH =  1.
+            SINPH =  0.
+         ELSE
+            COSTH = -1.
+            SINTH =  0.
+            COSPH =  1.
+            SINPH =  0.
+         ENDIF
+      ELSE
+         COSTH  = DUZ
+         DSITH  = SQRT((ONE+DUZ)*(ONE-DUZ))
+         SINTH  = DSITH
+         DNORM  = ONE/SQRT(DUX**2+DUY**2)
+         COSPH  = DUX*DNORM
+         SINPH  = DUY*DNORM
+      ENDIF
+*
+      END