[vtkusers] mapper SetResolveCoincidentTopologyToShiftZBuffer - Does this work ?

[David Netherway]

 Hello,

I am trying to have 3D lines always appear in front of other geometry and
volume ray cast images.

I thought to use mapper->SetResolveCoincidentTopologyToShiftZBuffer.

I have added a few test lines at the end of the disk.tcl demo - see below.

ResolveCoincidentTopologyToShiftZBuffer uses a function in
vtkOpenGlPolyDataMapper.cxx that maps the depth of the actor to a restriced
z range:
glDepthRange(zRes, 1.);

I map the line to the range 0.8 - 1.0 so that the line should always appear
in front when the camera is rotated but this is not the case for me.

I am using an NVIDIA GeForce 256 graphics card.  The card may not be
implementing glDepthRange.

Does anyone get the expected behaviour?

There is no test presently in vtk that tests this method. (My version is a
nightly CVS of about 3 months ago).

Thanks, David



# disk.tcl demo

package require vtk

package require vtkinteraction

# Create the RenderWindow, Renderer and both Actors

#

vtkRenderer ren1

vtkRenderWindow renWin

renWin AddRenderer ren1

vtkRenderWindowInteractor iren

iren SetRenderWindow renWin

vtkDiskSource disk

disk SetInnerRadius 1.0

disk SetOuterRadius 2.0

disk SetRadialResolution 1

disk SetCircumferentialResolution 20

vtkPolyDataMapper diskMapper

diskMapper SetInput [disk GetOutput]

vtkActor diskActor

diskActor SetMapper diskMapper

# Add the actors to the renderer, set the background and size

#

ren1 AddActor diskActor

ren1 SetBackground 0.1 0.2 0.4

renWin SetSize 200 200

# Get handles to some useful objects

#

iren AddObserver UserEvent {wm deiconify .vtkInteract}

iren Initialize

renWin Render



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

wm withdraw .

#----------added test code----------------------------

vtkLineSource testLine

testLine SetPoint1 0 0 0

testLine SetPoint2 2.5 0.0 1.0

vtkPolyDataMapper testLineMapper

testLineMapper SetInput [testLine GetOutput]

vtkActor testLineActor

testLineActor SetMapper testLineMapper

[testLineActor GetProperty] SetColor 1.0 0.0 0.0

ren1 AddActor testLineActor

testLineMapper SetResolveCoincidentTopology 1

testLineMapper SetResolveCoincidentTopologyToShiftZBuffer

testLineMapper SetResolveCoincidentTopologyZShift 0.8

#---- end test code --------------------------------