# clawpack/applications/euler/3d/ForwardFacingStep/src/physbd3.f

```!-----------------------------------------------------------------------
! Physical boundary conditions
! Interface:
!   mx,my,mz  := shape of grid
!
!   u(,) := grid function
!
!   lb(3) := lower bound for grid
!   ub(3) := upper bound for grid
!   lbbnd(3) := lower bound for boundary region
!   ubnd(3) := upper bound for boundary region
!   shapebnd(3) := shape of boundary region
!   xc(3) := lower left corner of grid
!   dx(3) := grid spacing
!   dir := at which side of the grid is the boundary?
!   bnd(,2,3) := lower left and upper right corner of global grid and
!      of mb-1 internal boundary regions
!
! Copyright (C) 2002 Ralf Deiterding
! Brandenburgische Universitaet Cottbus
!
! Copyright (C) 2003-2007 California Institute of Technology
! Ralf Deiterding, ralf@amroc.net
!
!-----------------------------------------------------------------------

subroutine physbd(u,mx,my,mz,lb,ub,lbbnd,ubbnd,shapebnd,
&     xc,dx,dir,bnd,mb,time,meqn)

implicit double precision (a-h,o-z)
include  "cuser.i"

integer   meqn, mx, my, mz, mb, dir
integer   lb(3), ub(3), lbbnd(3), ubbnd(3), shapebnd(3)
double precision u(meqn,mx,my,mz), xc(3), dx(3), bnd(mb,2,3), time

!      Local variables
integer   i, j, k, imin, imax, jmin, jmax, kmin, kmax, m
integer   stride, getindx, isym, jsym, ksym
integer   isx(5), isy(5), isz(5)
c
data isx /1,-1,1,1,1/
data isy /1,1,-1,1,1/
data isz /1,1,1,-1,1/

!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
!      See definition of member-function extents() in BBox.h
!      for calculation of stride

stride = (ub(1) - lb(1))/(mx-1)
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
!     Find working domain

imin = getindx(max(lbbnd(1), lb(1)), lb(1), stride)
imax = getindx(min(ubbnd(1), ub(1)), lb(1), stride)

jmin = getindx(max(lbbnd(2), lb(2)), lb(2), stride)
jmax = getindx(min(ubbnd(2), ub(2)), lb(2), stride)

kmin = getindx(max(lbbnd(3), lb(3)), lb(3), stride)
kmax = getindx(min(ubbnd(3), ub(3)), lb(3), stride)

if(imax .gt. mx .or. jmax .gt. my .or. kmax .gt. mz .or.
&     imin .lt. 1 .or. jmin .lt. 1 .or. kmin .lt. 1) then
write(0,*)'INDEX ERROR in physbd'
end if

go to (100,200,300,400,500,600) dir+1

!        Left Side --- Inflow
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
100  continue
do 110 i = imax, imin, -1
if (xc(1)+(i-0.5d0)*dx(1).lt.bnd(1,1,1)) then
do 120 k = kmin, kmax
do 120 j = jmin, jmax
do 120 m = 1, meqn
u(m,i,j,k) = qin(m)
120        continue
endif
110  continue
return

!        Right Side --- Outflow and fixed wall
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
200  continue
do 210 i = imin, imax
if (xc(1)+(i-0.5d0)*dx(1).gt.bnd(1,2,1)) then
do 220 k = kmin, kmax
do 220 j = jmin, jmax
do 220 m = 1, meqn
u(m,i,j,k) = u(m,i-1,j,k)
220        continue
else if (xc(1)+(i-0.5d0)*dx(1).gt.bnd(2,1,1)) then
isym = 2*imin-1-i
do 230 k = kmin, kmax
do 230 j = jmin, jmax
do 230 m = 1, meqn
u(m,i,j,k) = u(m,isym,j,k)*isx(m)
230        continue
endif
210  continue
return

!        Bottom Side --- Symmetry and fixed Wall
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
300  continue
do 310 j = jmax, jmin, -1
if (xc(2)+(j-0.5d0)*dx(2).lt.bnd(1,1,2).or.
&        xc(2)+(j-0.5d0)*dx(2).lt.bnd(2,2,2)) then
jsym = 2*jmax+1-j
do 330 k = kmin, kmax
do 330 i = imin, imax
do 330 m = 1, meqn
u(m,i,j,k) = u(m,i,jsym,k)*isy(m)
330        continue
endif
310  continue
return

!        Top Side --- Fixed Wall
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
400  continue
do 410 j = jmin, jmax
if (xc(2)+(j-0.5d0)*dx(2).gt.bnd(1,2,2)) then
jsym = 2*jmin-1-j
do 420 k = kmin, kmax
do 420 i = imin, imax
do 420 m = 1, meqn
u(m,i,j,k) = u(m,i,jsym,k)*isy(m)
420        continue
endif
410  continue
return

!        Front side --- Symmetry and fixed Wall
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
500  continue
do 510 k = kmax, kmin, -1
if (xc(3)+(k-0.5d0)*dx(3).lt.bnd(1,1,3).or.
&        xc(3)+(k-0.5d0)*dx(3).lt.bnd(2,2,3)) then
ksym = 2*kmax+1-k
do 530 j = jmin, jmax
do 530 i = imin, imax
do 530 m = 1, meqn
u(m,i,j,k) = u(m,i,j,ksym)*isz(m)
530        continue
endif
510  continue
return

!        Back Side --- Fixed Wall
!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
600  continue
do 610 k = kmin, kmax
if (xc(3)+(k-0.5d0)*dx(3).gt.bnd(1,2,3)) then
ksym = 2*kmin-1-k
do 620 j = jmin, jmax
do 620 i = imin, imax
do 620 m = 1, meqn
u(m,i,j,k) = u(m,i,j,ksym)*isz(m)
620        continue
endif
610  continue
return

end
```