Eye-Dome Lighting: vtkEDLShading (example request)

[banesullivan]

Could someone share an example of how to use the vtkEDLShading class in VTK?

This is commonly used in ParaView but I can’t seem to find any examples using it in pure-VTK.

Any help would be much appreciated!

[Michael (Michael Migliore (Kitware))]

Hi,
Please have a look at https://vtk.org/Wiki/VTK/MultiPass_Rendering
This page explains how render passes work.

[banesullivan]

Thanks, @Michael: that helped me figure out what I need to implement. I did some searching around in the VTK tests and converted the EDL cpp test case to Python (see snippet below). This was actually rather easy to implement and I added an option to vtki to plot with eye dome lighting! See https://github.com/vtkiorg/vtki/pull/128

General Useage

A general solution to use Eye Dome Lighting on a renderer:

...
renderer = vtk.vtkRenderer()
...
# create the basic VTK render steps
basic_passes = vtk.vtkRenderStepsPass()
# blur the resulting image
# The blur delegates rendering the unblured image to the basic_passes
edl = vtk.vtkEDLShading()
edl.SetDelegatePass(basic_passes)
#tell the renderer to use our render pass pipeline
glrenderer = vtk.vtkOpenGLRenderer.SafeDownCast(renderer)
glrenderer.SetPass(edl)
...

Example of Eye Dome Lighting

And the converted, simplified test case:

import vtk

renderer = vtk.vtkRenderer()
renderer.SetBackground(0.3, 0.4, 0.6)
renderWindow = vtk.vtkRenderWindow()
renderWindow.SetSize(600, 600)
renderWindow.AddRenderer(renderer)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renderWindow)

# Read poly data
filename = 'foo.vtp'
reader = vtk.vtkXMLPolyDataReader()
reader.SetFileName(filename)
reader.Update()
mesh = reader.GetOutput()

mapper = vtk.vtkPolyDataMapper()
mapper.SetInputDataObject(mesh)

actor= vtk.vtkActor()
actor.SetMapper(mapper)
renderer.AddActor(actor)

# create the basic VTK render steps
basicPasses = vtk.vtkRenderStepsPass()
# blur the resulting image
# The blur delegates rendering the unblured image
# to the basicPasses
edl = vtk.vtkEDLShading()
edl.SetDelegatePass(basicPasses);
# tell the renderer to use our render pass pipeline
glrenderer = vtk.vtkOpenGLRenderer.SafeDownCast(renderer);
glrenderer.SetPass(edl)

# And view it
iren.Start()

[banesullivan]

One follow up question: is it possible to not shade specific actors like scalar bars? See image below where a scalar bar is shaded and looks not great. I know this is implemented in ParaView, but not sure how

[Michael (Michael Migliore (Kitware))]

Hi,
Nice screenshot!

This should be possible if you render opaque/translucent geometry with the EDL render pass and render overlay separately and mix them up (using vtkSequencePass I guess).
See vtkOpaquePass and vtkOverlayPass.
Let me know if you manage to get something working.

[marcomusy]

you might render it on a different layer (see bgImage.py), something like

 ...
                        self.backgroundRenderer = vtk.vtkRenderer()
                        self.backgroundRenderer.SetLayer(0)
                        self.backgroundRenderer.InteractiveOff()
                        self.backgroundRenderer.SetBackground(1, 1, 1)
                        arenderer.SetLayer(1)
                        self.renwindow.SetNumberOfLayers(2)
                        self.renwindow.AddRenderer(self.backgroundRenderer)
                        self.backgroundRenderer.AddActor(image_actor)

[banesullivan]

I ended up getting this to work in https://github.com/pyvista/pyvista/pull/367 by using 2 layers of vtkRenderers. I only run the EDL shading pass on the renderer layer with data and leave another renderer to hold all the axes grid, scalar bar, etc. actors.

One problem I’m running into right now is how the axes grid appears above the data in the scene when it should be behind.