def DoCoProcessing(datadescription):
  timestep = datadescription.GetTimeStep()

  grid = datadescription.GetInputDescriptionByName("input").GetGrid()
  pressure = grid.GetPointData().GetArray('Pressure')

  grid.GetPointData().SetScalars(pressure)
  obj.SetOutput(grid)

  # get global range of Pressure
  di = trivialproducer.GetDataInformation(0)
  trivialproducer.UpdatePipeline()
  di.Update()
  pdi = di.GetPointDataInformation()
  ai = pdi.GetArrayInformation('Pressure')
  pressurerange = ai.GetComponentRange(0)

  contour.Isosurfaces = .5*(pressurerange[0]+pressurerange[1])

  # now output the results to the screen as well as taking
  # a screen shot of the view
  #setup a window
  rep = Show(contour)
  ren = Render()

  #set the background color
  ren.Background=[1,1,1]  #white

  #set image size
  ren.ViewSize = [200, 300] #[width, height]

  #set representation
  rep.Representation="Surface"

  #save screenshot
  gridimagefilename = 'CPGrid'+str(timestep) + '.png'
  WriteImage(gridimagefilename)

  rep = Show(trivialproducer)
  rep.LookupTable = MakeBlueToRedLT(pressurerange[0], pressurerange[1])
  rep.ColorArrayName = 'Pressure'
  rep.ColorAttributeType = 'POINT_DATA'
  #set representation
  rep.Representation="Surface"
  rep = Show(contour)
  #set the background color
  ren = Render()
  ren.Background=[1,1,1]  #white

  pressureimagefilename = 'CPPressure'+str(timestep) + '.png'
  WriteImage(pressureimagefilename)

  # explicitly delete the proxies -- may have to do this multiple times
  tobedeleted = GetNextProxyToDelete()
  while tobedeleted != None:
      Delete(tobedeleted)
      tobedeleted = GetNextProxyToDelete()

def GetNextProxyToDelete():
  iter = servermanager.vtkSMProxyIterator()
  iter.Begin()
  while not iter.IsAtEnd():
    if iter.GetGroup().find("prototypes") != -1:
       iter.Next()
       continue
    proxy = servermanager._getPyProxy(iter.GetProxy())
    proxygroup = iter.GetGroup()
    iter.Next()
    if proxygroup != 'timekeeper' and proxy != None and proxygroup.find("pq_helper_proxies") == -1 :
        return proxy

  return None

def RequestDataDescription(datadescription):
  time = datadescription.GetTime()
  timestep = datadescription.GetTimeStep()
  if timestep % 20 == 0:
    # add in some fields
    #print 'added Pressure and wanting to do coprocessing'
    datadescription.GetInputDescriptionByName("input").AddPointField("Pressure")
    datadescription.GetInputDescriptionByName('input').GenerateMeshOn()
  return

# the code below is needed to import objects from paraview.simple
# plus the definition of vtkTrivialProducer into this python script.
try: paraview.simple
except: from paraview.simple import *

trivialproducer = TrivialProducer()
contour = Contour(Input=trivialproducer)
obj = trivialproducer.GetClientSideObject()


