VTK:update image in renderwindow fails in specific cases

Question

-----UPDATE and Solution-------

Unless

renderwindow.Render()

is called in the

UpdateData()

function the behavior remains erratic. So the renderwindow needs to be updated as well.

---

I am trying to visualize really large images in vtk. For this i have subdivided them into tiles and now i am trying to browse through them adjusting the camera as i go.

For the time being i have assigned the WASD keys to functions that do move up down right and left. whenever i move up and down in my dataset the view is updated without problem however the image does not move whenever i move right and left. If i move up and down again the image jumps to the correct position. In short only right and left do not work. This puzzles me as i use virtually the same function for the movements , appended is my sample code:

# current position is a  list  with x y z coordinates as filenames
#reader
metaImageReader = vtk.vtkMetaImageReader()
metaImageReader.SetFileName(filefolder + "%03d_%03d_%03d"%(currentPosition[0],currentPosition[1], currentPosition[2]) + extension)
metaImageReader.SetDataScalarTypeToUnsignedChar()
#metaImageReader.SetFileDimensionality(3)
metaImageReader.Update()

#create renderwindow
renWin = vtk.vtkRenderWindow()
renWin.SetSize(600,300)



#create renderer1
renderer_2d = vtk.vtkRenderer()
renderer_2d.SetViewport(0,0,0.5,1)
renderer_2d.SetBackground(1.0,1.0,1.0)
renWin.AddRenderer(renderer_2d)

#create renderer2
renderer_3d = vtk.vtkRenderer()
renderer_3d.SetViewport(0.5,0,1,1)
renderer_3d.SetBackground(0.0,0.0,0.0)
renWin.AddRenderer(renderer_3d)


mapper = vtk.vtkImageSliceMapper()
mapper.SetInput(metaImageReader.GetOutput())
mapper.Update()

actor = vtk.vtkImageSlice()
actor.SetMapper(mapper)
actor.Update()




renderer_2d.AddActor(actor)


def updateData():
    global metaImageReader, actor, mapper, currentPosition, filefolder, extension, viewer, origin
    metaImageReader.SetFileName(filefolder + "%03d_%03d_%03d"%(currentPosition[0],currentPosition[1], currentPosition[2]) + extension)
    metaImageReader.Update()
    mapper.Update()
    actor.Update()


def keypress(obj,event):

    key = obj.GetKeySym()
    print key
    if key == "w":
        print "w"
        moveUp()
    elif key == "s":
        print "s"
        moveDown()
    elif key == "d":
        print "d"
        moveRight()
    elif key == "a":
        print "a"
        moveLeft()


def moveUp():
    global currentPosition
    x,y,z = currentPosition
    y = y-1
    currentPosition = x,y,z
    updateData()

def moveDown():
    global currentPosition
    x,y,z = currentPosition
    y = y+1
    currentPosition = x,y,z
    updateData()

def moveRight():

    global currentPosition
    x,y,z = currentPosition
    x = x+1
    currentPosition = x,y,z
    updateData()

def moveLeft():

    global currentPosition
    x,y,z = currentPosition
    x = x-1
    currentPosition = x,y,z
    updateData()

#create interactor
iren = vtk.vtkRenderWindowInteractor()
iren.AddObserver("KeyPressEvent", keypress)
iren.SetRenderWindow(renWin)

#visualization pipeline
# Source -> Reader -> Filter -> Mapper -> Actor
iren.Start()
renWin.Render() 

Answer 1

Unless

renderwindow.Render()

is called in the

UpdateData()

function the behavior remains erratic. So the renderwindow needs to be updated as well.