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

[James C. Robinson]

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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