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

Jeff Lee jeff at cdnorthamerica.com
Thu Mar 18 09:46:42 EST 2004 

Hi,
There are indeed many ways to skin the proverbial cat, and it is easy 
for a novice to get lost.  If you don't already have the vtk users and 
the VTK book guide, get them.  Other available sources of info include 
vtk doxygen man-pages, mailing lists, and the examples.  You won't get 
much sympathy from people on this mailing list if you just complain - 
i've seen your pictures and posts, and without some example programs 
that demonstrate your problems, nobody can help you.  Cobble up some 
examples.  As for your examples below, the user-guide contains basic 
pipelines for the things you describe, but for free you can look at the 
tcl/python/c++/java examples to see how the pipelines are set up.  There 
are links from the man-pages to most examples/tests and even pictures of 
the output in many cases.  In my opinion, it is very clear as to the 
differences in the filters you allude to below, just from reading the 
man-pages.  RTFM.
Regards,
-Jeff

James C. Robinson wrote:

>John,
>
>Good to hear from you. I appreciate where you're coming from, but I don't
>want to get into the world of patches etc. I want a working solution (my
>issues are that of FE pure, mesh generation tailored for my problem,
>designing the look and feel of the interface):- graphics is something that I
>want to be able to take for granted - this is why I have opted for a 3rd
>party solution.
>
>You see, you still haven't addressed (a) the issue of why we have so many
>objects that replicate so many similar functionalities and (b) why at least
>very specific explanations of these objects aren't given (preferably
>referring to the other similar objects and clearly distinguishing why one
>might want to use one as opposed to the other).
>
>Surely there is room for a very clear document that says explicitly, for
>example:
>Heading: Representation of finite element quadratic hexahedra mesh.
>	Topic 1: Displaying element materials. Take the following steps:
>1. Use a vtkUnstructuredGridReader to take in the FE mesh as a file.
>2. Now set the vtkUnstructuredGridReader as input to a vtkGeometryFilter(? I
>don't think this is the best one, I will try a vtkDataSetSurfaceFilter
>instead and see do things improve). Then use a vtkPolyDataMapper (I am going
>to try a vtkDataSetMapper instead and see if this improve things|).
>3. If using MFC C++ under windows, send your vtkPolyDataMapper output
>through a vtkActor and add this to the vtkRenderer.
>	Topic 2: Displaying a scalar field. Take the following steps: etc.
>
>You see what I mean? There must be a simple pipeline type diagram that could
>be supplied, with a tcl example code. NB: I would imagine that FE type
>applications could form a substantial section of the user base. Why should
>we have to keep experimenting all of us individually? It is a total waste of
>time. If we are a real community (of users) we should be able to create a
>structure (on the web) where such valuable info is stored. We could have a
>proforma document to fill in and submit. I feel the suggestion of just going
>to the mail list and doing a search is a total cop out. There must be
>thousands e-mail, all very weakly titled and not in a structure that would
>make it easy to find anything specific.
>
>All your comments (put downs, wake up calls etc.) are welcome.
>
>Regards,
>
>Jim
>
>______________________
>
>James C. Robinson, PhD,
>Chartered Engineer,
>Kepler Simulation Systems Ltd.,
>42 Rivergrove,
>Glanmire, Co. Cork,
>Eire
>
>Tel:         +353-21-4822028
>Tel:         +353-87-2393010
>Fax:        +353-21-4822028
>E-mail:     j.robinson at kepler-systems.com
>______________________
>
>-----Original Message-----
>From: John Biddiscombe [mailto:jbiddiscombe at skippingmouse.co.uk]
>Sent: 18 March 2004 13:12
>To: j.robinson at kepler-systems.com
>Subject: Re: [vtkusers] I think this is the problem......
>
>JIm,
>
>The sad news is that you're going to have to bite the bullet and use trial
>and error like all of us to learn the "best" way to do things!
>
>When you discover stuff that needs improving, submit patches for docs or
>other to the bug tracker. It's all one can do. We (developers) try our best,
>but we only usually fix the stuff which we need at any particular moment.
>
>JB
>
>
>----- Original Message -----
>From: "James C. Robinson" <j.robinson at kepler-systems.com>
>To: "Vtk Users" <vtkusers at vtk.org>
>Sent: Thursday, March 18, 2004 12:12 PM
>Subject: [vtkusers] I think this is the problem......
>
>
>  
>
>>Dear All,
>>
>>I still haven't resolved my overall problems (getting v4.4 to work the
>>    
>>
>same
>  
>
>>as v4.0, implementing the quad hexes etc.) but I am starting to realise
>>    
>>
>part
>  
>
>>of the problem. VTK is not documented well enough (at least the online
>>help). You see, there are many objects which seem to overlap in
>>functionality (e.g vtkGeometryFilter, vtkExtractUnstructuredGrid,
>>vtkDataSetSurfaceFilter). How is one supposed to know which one to use?
>>    
>>
>The
>  
>
>>descriptions are not detailed enough to indicate why one should be used as
>>opposed to another, why they are derived off different objects but seem to
>>achieve a lot of the same thing?
>>
>>Undoubtedly I am once again displaying my ignorance, but I am really only
>>concerned with making my application work. My objective in using vtk was
>>that it seemed to have specifically tailored functionality that fit in
>>easily with FE analysis. To a great extent it is true, but it is in the
>>finer detail that I am feeling let down.
>>
>>My objective is to view a 3D 20 noded (quadratic) hexahedral mesh, with
>>material, pressure and flow velocity data. I have a MFC C++ (v6) version
>>that almost works, where I can view and cut the mesh anyway I want. I can
>>view the flow vectors (as arrows) on any plane, I can view an iso
>>    
>>
>(pressure)
>  
>
>>surface, I can even create a streamtube (although this does lock up).
>>However, I am running into trouble with the v4.2-4.4 VTK releases - I
>>    
>>
>can't
>  
>
>>control the transparency of my objects etc. I may be using the wrong
>>filters.... But how am I supposed to know. Surely there must be a
>>    
>>
>definitive
>  
>
>>"best way" to view such a mesh and manipulate in the manner that I want.
>>
>>Your sin desperation...
>>
>>Jim
>>
>>______________________
>>
>>James C. Robinson, PhD,
>>Chartered Engineer,
>>Kepler Simulation Systems Ltd.,
>>42 Rivergrove,
>>Glanmire, Co. Cork,
>>Eire
>>
>>Tel:         +353-21-4822028
>>Tel:         +353-87-2393010
>>Fax:        +353-21-4822028
>>E-mail:     j.robinson at kepler-systems.com
>>______________________
>>
>>
>>
>>_______________________________________________
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>>Please keep messages on-topic. Check the FAQ at:
>>    
>>
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>  
>
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>>    
>>
>
>
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