[vtkusers] Re: dark printing and clipboard

Nigel Nunn nNunn at ausport.gov.au
Tue Apr 15 10:54:12 EDT 2003

Hi Paul, 
I've also struck the problem of images rendering fine on-screen 
but losing their user-defined lighting when rendered off-screen. 
e.g. into the clipboard.  One place damage may occur is here: 
void vtkOpenGLRenderer::DeviceRender(void) 
  this->ClearLights();                  <--- clears all lights! 
  this->UpdateLights();             <--- not properly restored? 
If no user-defined lights are active, then UpdateLights() adds 
a headlight and at least there is some light in the image.  But 
(guessing here) if we have added a custom set of lights, then 
these are lost in the call to ClearLights(); but not restored 
in UpdateLights().  And since there is a "non-zero" number of 
lights, the default headlight is not added, and scene is dark. 
My (solution :-) when making movies, is to turn off light-kits 
or other user-defined lights, and adjust the scene to be visible 
with just the default headlight (which is better than nothing). 
If I get time, I plan to build a debug Vtk and trace this. 
Hope you can find a better fix! 
> I am displaying 2 surfaces made up of triangles. Hence the 
> top & bottom lut which use scalars attached to each surface. 
> I'm using the vtlLightinghKit so my theory is that the surfaces 
> have an "intrinsic" color which is changed (lightened) by the 
> lighting kit to produce what I see on the screen. When I print 
> only get those "intrinsic" colors. Thats why the 2D scale bar 
> gets displayed ok..... I think
> So how do I get vtk to give me the post processed pixels for 
> printing? 
> Hi
> VTK 4.0
> I'm trying to get my MFC printing working
> I'm using pretty much the same code as in the examples and 
> I've implemented clipboard copying but in both cases my plots 
> come out dark
> I also print out a vtkScalarbarActor which displays perfectly, 
> so I know i'm doing something wrong

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