[vtkusers] I think this is the problem......

[Sean McInerney]

Amazingly, this reply actually answers the original question!

I support the tangential ideas regarding a need for application level 
VTK documentation, but this is beside my point. Rather than huffing and 
puffing and lording one's experience over another's lack, contributors 
to this list might apply vtkPeopleSkillsFilter to their replies. Be sure 
to set ATFQ to "On" (answer the f***ing question). Note that use of this 
option may result in empty output for some. In other words, 
condescension and dismissal are never appropriate when attempting to 
offer help. Even the best advice may go unheeded when paired with abuse. 
Vent your personal frustrations elsewhere.

Less need for replies like this will also result in less search engine 
chaff.

-Sean

> Date: Thu, 18 Mar 2004 18:19:39 +0000
> From: Goodwin Lawlor <goodwin.lawlor at ucd.ie>
> Subject: Re: [vtkusers] I think this is the problem......
> To: j.robinson at kepler-systems.com
> Cc: vtkusers at vtk.org
> Reply-To: goodwin.lawlor at ucd.ie
> Organization: University College Dublin
> 
> Hi Jim,
> 
> I agree with Joey- it would be impracticle to have a step-by-step guide
> to every possible pipeline (or pipeline type) in VTK. A wiki would be a
> good way to have a stab at it though...
> 
> If you're relying on the online documentation to learn VTK I'm not
> surprised you're frustrated. Its really just a quick reference for class
> methods and properties. The user guide only really talks you though
> examples.
> 
> To learn the theory/concept of VTK you have to get the VTK textbook.
> 
> The best way to learn VTK is to look at and run the example tcl (or
> python) scripts. Then start editing them and seeing the affects.
> 
> One good thing about open source software is that the source code itself
> is documentation... Do a string search for a class name in the source
> tree to see how the developers used the class. There are also some
> comments in the .cxx files that may be helpful.
> 
> Also it may help to prototype your pipeline in tcl before you starting
> coding in c++... Its much quicker to edit and run scripts.
> 
> One area where I found a derth of information is managing VTK pipelines
> inside an application and what the correct way to do this. You may know
> MFC or tcl/tk and know VTK well but putting them together....
> 
> Just on your mapper questions:
> 
> One rule of thumb: 
> vtkUnstructuedGrid/vtkStructuredGrid... Use vtkDataSetMapper
> vtkPolyDataMapper... Use vtkPolyDataMapper
> 
> If fact you can think of vtkDataSetMapper as a helper class that
> contains a vtkPolyDataMapper and a vtkDataSetSurfaceFilter. Inside
> vtkDataSetMapper, vtkDataSetSurfaceFilter extracts cells for the
> internal instance of vtkPolyDataMapper. Why do this? vtkPolyDataMapper
> is the interface to OpenGL... A vtkUnstructuredGrid contains (3d) cells
> that OpenGL doesn't recognise so in order to render a hex, it must be
> broken down into its constituent quads which OpenGL can render.
> 
> So...
> 
> vtkUnstructuredGrid->vtkDataSetMapper-> is the same as
> vtkUnstructuredGrid->vtkDataSetSurfaceFilter->vtkPolyDataMapper->
> 
> vtkDataSetSurfaceFilter is a quicker version of vtkGeometryFilter. As
> far as I can remember, vtkDataSetMapper used to contain
> vtkGeometryFilter instead.
> 
> Hope this helps... If the birth of a good wiki is the product of you
> frustrations then they wont have been in vain!
> 
> Goodwin