proc drawselectionsphere { rad cx cy cz } {
  draw material Transparent
  set solvdraw [format "draw sphere { $cx $cy $cz } radius $rad"]
  eval $solvdraw
  display update 
}


proc makewatersphere { rad cx cy cz } {
  echo "generating water box of size [expr $rad * 2] cubed"
  package require solvate
 
  set solvcmd [format "solvate -o new -minmax {{ -$rad -$rad -$rad} {$rad $rad $rad}} -t 1.0"] 
  puts $solvcmd
  # run the solvate command 
  eval $solvcmd

  mol new combine.psf 
  mol addfile combine.pdb
  drawselectionsphere $rad $cx $cy $cz
 
  echo "generating water sphere of radius $rad from box, in VMD"
  set r2 [expr $rad*$rad] 
  set wat2keep   [atomselect top "same residue as ((sqr(x-$cx)+sqr(y-$cy)+sqr(z-$cz)) <= $r2)"]
  $wat2keep writepdb watersphere.pdb
  $wat2keep delete
  mol delete top
}

proc makewaterspherepsf {} {
  package require psfgen
  set solversion [package require solvate]
  
  echo "generating water sphere PSF, via psfgen"
  set oldctx [psfcontext new]

  topology $env(VMDDIR)/plugins/noarch/tcl/solvate$solversion/wat.top
 
  segment SOLV {
    auto none
    pdb watersphere.pdb
  }

  coordpdb watersphere.pdb SOLV

  writepsf watersphere.psf
  writepdb watersphere.pdb
  psfcontext $oldctx delete
}

echo "deleting any old files"
file delete -force watersphere.psf
file delete -force watersphere.pdb

makewatersphere 10.0 20 20 20

mol new watersphere.pdb
makewaterspherepsf

mol delete top
mol new watersphere.psf 
mol addfile watersphere.pdb