Hardware clipping planes in VTK

[David Gobbi]

On Tue, 29 Jun 1999, Lisa Sobierajski Avila wrote:

> Since you have named them "ClippingPlanes" it does not seem necessary to
> have a more general representation (because even if in the future OpenGL
> does allow more general clipping functions you would have to change the
> name anyway, right?). 

You got me there.  Time for me to bring the old grey matter in for a
tune-up.

> If vtkImplicitFunctionCollection is the best way to
> store this internally, that's fine (although I think there is probably a
> simpler way) but you might want to add access methods (add/remove clipping
> plane) that do the error checking when you set the clipping plane rather
> than at render time. (So when a user adds a plane you can make sure it is
> truly a plane and that you have not exceeded the limit) What do you think?

Yes, internalizing the vtkImplicitFunctionCollection would be a clean
solution.  I'll make the changes.

 - David

> Lisa
> 
> 
> At 04:05 PM 6/29/99 -0400, David Gobbi wrote:
> >Hi Lisa,
> >
> >It would be easy to to add the SetClippingPlanes method to
> >vtkDataSetMapper (it will just call the same method in its
> >internal vtkPolyDataMapper), so I will do that.
> >
> >I used vtkImplicitFunctions because it already existed, there
> >is no collection of vtkPlanes.  Instead, an error is reported 
> >at render time if any of the functions is not a plane, or
> >if too many planes are specified.  (Who knows, future versions
> >of OpenGL might allow more complicated clipping functions -- I
> >prefer to keep things general).
> >
> > - David
> >
> >On Tue, 29 Jun 1999, Lisa Sobierajski Avila wrote:
> >
> >> Hello David,
> >> 
> >> Now that XGL and Starbase are gone, this seems like a good addition - at
> >> least until we add some new graphics language that doesn't support hardware
> >> clipping! :-)
> >> 
> >> Why did you chose to add these changes to vtkPolyDataMapper instead of
> >> vtkDataSetMapper? It would seem that they could be added to
> >> vtkDataSetMapper which would allow for clipping of more than just polydata.
> >> And why did you add vtkImplicitFunctions instead of some other
> >> specification that allows for only planes? The implicit function seems too
> >> general - doesn't OpenGL require simple planes for hardware clipping?
> >> 
> >> Lisa Avila
> >> 
> >> 
> >> At 02:53 PM 6/29/99 -0400, David Gobbi wrote:
> >> >
> >> >I have added hardware clipping planes to VTK, and would
> >> >like to get some feedback before contributing the change
> >> >to Kitware.
> >> >
> >> >All of the changes are limited to vtkPolyDataMapper, which has
> >> >the following new methods:
> >> >
> >> >void vtkPolyDataMapper::SetClippingPlanes(vtkImplicitFunctionCollection)
> >> >vtkImplicitFunctionCollection vtkPolyDataMapper::GetClippingPlanes()
> >> >
> >> >These allow you to specify up to 6 clipping planes which are
> >> >handled by OpenGL.  This is equivalent to piping vtkPolyData
> >> >through a set of vtkClipPolyData filters.  When you are moving
> >> >the clipping planes around, doing the clipping in hardware 
> >> >makes the rendering go several times faster.
> >> >
> >> > - David
> >> >
> >> >--David Gobbi, MSc                    dgobbi at irus.rri.on.ca
> >> >  Advanced Imaging Research Group
> >> >  Robarts Research Institute, University of Western Ontario
> >> >
> >> >
> >> >
> >>
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> >> 
> >
> >
> >
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