[vtkusers] Removing lighting from points, lines, and wireframe

[David Pont]

I have experienced invisible (black) lines, so I would like to see some 
option to manage this. Of the four options I would vote for "3) Make it an 
option where the default is to not use lighting (1) but
it could be turned on".
Would it be more compatible to default to lighting on (the current 
behaviour), but it can turned off? or is that already possible?.

To digress: OpenGL provides the following material properties: GL_AMBIENT, 
GL_DIFFUSE, GL_SPECULAR, GL_EMISSION, GL_SHININESS. When using OpenGL some 
years back (before I discovered vtk) I used the EMISSION property at times 
to avoid lighting effects on surfaces. For scientific visualisation this is 
arguably an essential option. While shading is an important visual clue to 
shape, it can be misleading for interpretation of colour as a representation 
of attribute data.

vtkProperty provides: SetAmbient, SetDiffuse, SetSpecular, SetSpecularPower, 
SetOpacity. Could a SetEmitted be added?. This could be used in combination 
with SetAmbient etc to obtain the full range of shading, including none. Or 
am I just misunderstanding and mis-using lighting in general!

  regards
     Dave Pont


>From: "Ken Martin" <ken.martin at kitware.com>
>To: "Vtk-Developers at Public. Kitware. Com" 
><vtk-developers at public.kitware.com>, "Vtkusers at Public. Kitware. Com" 
><vtkusers at public.kitware.com>
>Subject: [vtkusers] Removing lighting from points, lines, and wireframe
>Date: Mon, 1 Oct 2001 12:04:13 -0400
>
>Hello Folk,
>
>We are considering removing lighting from points, lines, and wireframe
>in VTK and I wanted to get some feedback on the idea. Currently
>lighting is applied to a wireframe mesh by default and this frequently
>causes confusion because parts of the mesh are black (or near black)
>due to lighting considerations when they expect the mesh to show up.
>The same thing happens less commonly for lines and points. One
>suggestion is
>
>1) remove lighting from lines, points, and wireframes
>
>2) remove lighting from wireframes, but leave it on for points and
>lines if they have normals
>
>3) Make it an option where the default is to not use lighting (1) but
>it could be turned on
>
>4) leave it the way it is, I like my wireframes shaded
>
>Thanks
>Ken
>
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