cr_spline_knots.F

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!||====================================================================
!||    cr_spline_knots        ../common_source/tools/interpolation/cr_spline_knots.F
!||--- called by ------------------------------------------------------
!||    cr_spline_length       ../common_source/tools/interpolation/cr_spline_length.F
!||    cr_spline_point_proj   ../common_source/tools/interpolation/cr_spline_point_proj.F
!||    detcord                ../starter/source/initial_conditions/detonation/detcord.F
!||====================================================================
      SUBROUTINE cr_spline_knots( PTS , KNOTS, ALPHA)
C-----------------------------------------------
C   I m p l i c i t   T y p e s
C-----------------------------------------------
#include      "implicit_f.inc"
C-----------------------------------------------
C   D e s c r i p t i o n
C-----------------------------------------------
        ! computes knots for solving 4-point spline path.
        ! CATMULL-ROM PARAMETER
        !  ALPHA = 0.0 : uniform
        !  ALPHA = 0.5 : centripetal
        !  ALPHA = 1.0 : chordal
        !      INPUT  - PTS(0:3,:) are 4 control points
        !      INPUT  - ALPHA CCR SPLINE PARAMETER
        !      OUTPU  - KNOTS() : t0,t1,t2,t3
C-----------------------------------------------
C   D u m m y   A r g u m e n t s
C-----------------------------------------------
        my_real, INTENT(IN)    :: pts(0:3,3),  alpha
        my_real, INTENT(INOUT) :: knots(0:3)
C-----------------------------------------------
C   L o c a l   V a r i a b l e s
C-----------------------------------------------
        my_real :: x,y,z
C-----------------------------------------------
C   S o u r c e   L i n e s
C-----------------------------------------------
        knots(0)=0.0
        x=pts(1-1,1)-pts(1,1)
        y=pts(1-1,2)-pts(1,2)
        z=pts(1-1,3)-pts(1,3)
        knots(1)=knots(0)+ exp(alpha*log(sqrt(x*x+y*y+z*z)))
        x=pts(1,1)-pts(1+1,1)
        y=pts(1,2)-pts(1+1,2)
        z=pts(1,3)-pts(1+1,3)
        knots(2)=knots(1)+ exp(alpha*log(sqrt(x*x+y*y+z*z)))
        x=pts(1+1,1)-pts(1+2,1)
        y=pts(1+1,2)-pts(1+2,2)
        z=pts(1+1,3)-pts(1+2,3)
        knots(3)=knots(2)+ exp(alpha*log(sqrt(x*x+y*y+z*z)))
      END SUBROUTINE cr_spline_knots