[vtk] flipped normals question

[Randy Heiland]

When I apply a vtkTransform with a negative Scale component to an Actor, it
seems to "lose its normals" (ever have days like that?) -- at least the
transformed actor isn't lit (but you can see it by going into wireframe).

Included is a simple Python script; below it, a similar Tcl script where I've
tried introducing flipped normals, etc..  What am I missing?

thanks,
--Randy

----------------------------------------------------------
#!/usr/local/bin/python

from libVTKCommonPython import *
from libVTKGraphicsPython import *

ren = vtkRenderer()
renWin = vtkRenderWindow()
renWin.AddRenderer(ren)
renWin.SetSize(300,300)
iren = vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)

cone = vtkConeSource()
cone.SetResolution(8)
coneMapper = vtkPolyDataMapper()
coneMapper.SetInput(cone.GetOutput())

coneActor = vtkActor()
coneActor.SetMapper(coneMapper)

xform=vtkTransform()
xform.Identity()
xform.Translate(2,0,0)
xform.Scale(1,1,-1)

coneFlipActor = vtkActor()
coneFlipActor.SetMapper(coneMapper)
coneFlipActor.GetProperty().SetColor(1,0,0)
coneFlipActor.SetUserMatrix(xform.GetMatrix())

ren.AddActor(coneActor)
ren.AddActor(coneFlipActor)


# enable user interface interactor
iren.Initialize()

iren.Start()
----------------------------------------------------------

catch {load vtktcl}
# user interface command widget
source ../../examplesTcl/vtkInt.tcl


# create a rendering window and renderer
vtkRenderer ren1
  ren1 TwoSidedLightingOn

vtkRenderWindow renWin
    renWin AddRenderer ren1
vtkRenderWindowInteractor iren
    iren SetRenderWindow renWin

# create an actor and give it cone geometry
vtkConeSource cone
  cone SetResolution 8
vtkPolyDataMapper coneMapper
  coneMapper SetInput [cone GetOutput]
vtkActor coneActor
  coneActor SetMapper coneMapper

vtkTransform xform
  xform Identity
  xform Translate 2 0 0
  xform Scale 1 1 -1

vtkCleanPolyData cleaner
  cleaner SetInput [cone GetOutput]
#  coneFlipActor SetMapper coneMapper
  coneFlipActor SetMapper flipMapper
  [coneFlipActor GetProperty] SetColor 1 0 0
  coneFlipActor SetUserMatrix [xform GetMatrix]
  [coneFlipActor GetProperty] BackfaceCullingOff

# assign actors to the renderer
ren1 AddActor coneActor
ren1 AddActor coneFlipActor

# enable user interface interactor
iren SetUserMethod {wm deiconify .vtkInteract}
iren Initialize

# prevent the tk window from showing up then start the event loop
wm withdraw .

vtkPolyDataNormals normals
#  normals SetInput [cone GetOutput]
  normals SetInput [cleaner GetOutput]
  normals FlipNormalsOn

vtkPolyDataMapper flipMapper
  flipMapper SetInput [normals GetOutput]


vtkActor coneFlipActor



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