[vtk-developers] vtkGL2PSExporter: need feedback.

[Prabhu Ramachandran]

Hi,

Thanks again for the feedback.  Comments follow.

>>>>> "JL" == Jeff Lee <jeff at cdnorthamerica.com> writes:

    >>  I beg to differ.  Very few classes are used in every
    >> situation.  If vtkXYPlotActor belongs in VTK, a gl2ps writer
    >> would also make a good addition.
    >> 
    JL> I don't understand your comparison with vtkXYPlotActor here,
    JL> but it looks like you misunderstood my argument.  If someone

Very likely I misunderstood.  I thought your argument was that gl2ps
is not useful all the time for the different types of visualizations.
Mainly transparent actors and complex scenes.  So my argument was that
not all classes are useful all the time anyway and cited the example
vtkXYPlotActor.

    JL> has a scene and wants a hardcopy and uses your class, there is
    JL> a good chance that the resulting picture will be unacceptable.
    JL> There is no adjustable parameter to make your class produce an
    JL> acceptable picture if the user has transparency.  You will

So what?  There are limitations to everything.

    JL> also need to provide hooks for the sorting and culling
    JL> options.  In contrast, vtkWindowToImageFilter does work well
    JL> in all situations, with an adjustable parameter of

Unfortunately, it is not good enough in all situations.  Just imagine
generating 20 graphs (even simple 2D ones) and then realize that you
have to rescale the plots and the images show up badly.  Its worse if
its a paper that you sent a year ago and then they want nicer pictures
now and you need to figure out how to re-generate those 20 images.  If
the images were postscript there are no such issues.

I'll admit that this is a contrived example but I'm not buying the
argument that vector graphics are useless and can be replaced by
bitmapped images.

    JL> magnification, and produces quality hardcopy without trying to
    JL> turn your printer's postscript rendering engine into a gl JL>
    rendering engine.

Well, its unfortunate that the printer is treated like a rendering
engine but vector graphics has its uses.

[snip]

    JL> There is no such thing as gl to ps.  I feel like I'm arguing
    JL> about the principle of using postscript as a rendering engine.

If this argument holds then what do you say about VRML output?  Do you
think it is correct to use a web browser as a rendering engine?

Honestly, I dont care if it ends up that PS is being used as a
rendering engine.  My point is absolutely simple.  Vector graphics
output is useful and desired by quite a few folks.  VTK does not
generate vector graphics output at all even for the simplest of
scenes.  By adding vtkGL2PSExporter we allow people to try out gl2ps.
If it works for them fine if not let them go back to using images or
whatever is convenient.  Why deny someone the opportunity to use the
class.  Its not like this is the first time someone has asked for
this.  Besides if gl2ps was so evil why has it gotten to where it is
today (version 0.71)?

cheers,
prabhu