[Paraview] Simple Visualization

[David E DeMarle]

This is what I meant:

1) load the vtk file
ParaView now makes a pipeline that looks like this

     FileReader->Data

And the data is like so (just a list of points in space):
x1,y1,z1:
x2,y2,z2:
...

2) Apply the Calculator Filter to add a constant valued point
associated array to the data.

Now the Pipeline looks like this:
   FileReader->Data->Calculator->Data'

And Data looks the same as it did,
While Data' is a set of locations in space, each with an associated value:
x1,y1,z1:someconstant
x1,y1,z1:someconstant
...

3) save Data' to a file. Click on Calculator filter in pipelinebrowser
and select file->Save Data, and choose the VTK format.

4) compare the input and output files to see what the file should look
like to give each vertex file format for data with values

Now that the data has some value, the glyph filter has something to
work with to let it decide how large to make the polygons that make up
each sphere.

5) load Data' into VTK, apply the glyph filter and turn scaling by
scalar value on.

If the values meant something (like atomic number), instead of just
being a constant value, the glyph size would mean something. Without
that, the glyph filter just makes each sphere exactly 0.5 units wide
because it can not guess what you need it to look like.

I am quite surprised that povray will make a guess actually. How does
it know what radius to choose that looks right? Are you trying to draw
stars from your list of coordinates, apples int a bin, marbles on a
table, bubbles in a pint of beer, or atoms in a molecule?

cheers,
Dave

On Fri, Oct 31, 2008 at 1:08 PM, Lorenzo Isella
<lorenzo.isella at gmail.com> wrote:
> Hello,
> I installed from source version 3.4.2. Now I can follow your procedure.
> I generated the new vtk file (saved as ascii), but it is definitely
> different from what I started from:
>
> # vtk DataFile Version 3.0
> vtk output
> ASCII
> DATASET POLYDATA
> POINTS 250000 float
> 64.3441 20.798 26.378 64.3441 20.798 18.4467 66.0647 20.798 25.9853
> 67.4446 20.798 24.8849 68.2103 20.798 23.2948 68.2103 20.798 21.5299
> 67.4446 20.798 19.9398 66.0647 20.798 18.8394 65.5608 22.0147 25.9853
> 66.5365 22.9904 24.8849 67.0779 23.5319 23.2948 67.0779 23.5319 21.5299
> 66.5365 22.9904 19.9398 65.5608 22.0147 18.8394 64.3441 22.5187 25.9853
> 64.3441 23.8985 24.8849 64.3441 24.6643 23.2948 64.3441 24.6643 21.5299
> 64.3441 23.8985 19.9398 64.3441 22.5187 18.8394 63.1274 22.0147 25.9853
> [...]
>
> For instance, now there are many more points. The generated text file
> is above 20Mb, so it is not a piece of cake to look for its new
> features.
> Cheers
>
> Lorenzo
>
>
>
> 2008/10/31 Lorenzo Isella <lorenzo.isella at gmail.com>:
>> 2008/10/30 David E DeMarle <dave.demarle at kitware.com>:
>>>> Alright, we'll get to the bottom of this.
>>>> This is a list of what I do (which is clearly NOT working).
>>>> (1) open the .VTK file I emailed you.
>>>> (2)click apply
>>>> (3) I cannot select the calculator filter right now in the GUI hence
>>>
>>> I can not replicate that problem. As soon as I hit apply the
>>> calculator filter is an option. I am on paraview 3.4.
>>
>> This unexpected. I am on Debian testing and I have paraview 3.2.2.
>>
>>
>>>
>>>> (4) I apply a gliph filter and set the radius to 0.1
>>>> (5) I can now apply a calculator filter. I leave the defaults and
>>>> write 1 in the empty space before applying it
>>>> (6) nothing changes in the snapshot apart from the color
>>>
>>> It shouldn't. You have just associated some data with the polygonal
>>> spheres. You have not made them larger.
>>>
>>> The color changed because you now have some associated data, not just
>>> locations to work with, so paraview automatically colormaps the data.
>>> Your data is pretty boring (everything has the value 1.0), so the
>>> color is pretty lame, (everything is red).
>>
>> So this makes sense now.
>>
>>
>>>> (7) select again gliph filter, set sphere to radius 0.1 and click
>>>> apply (In the "scalar" field I now read "Result", so I thought
>>>> Paraview somehow had info about the previous filter I had applied),
>>>
>>> Yes, this second glyph filter now has something besides the x,y,z
>>> locations to work with. It has the same associated data that caused
>>> the color to change.
>>>
>>>> (8) Now everything is red and I have no idea of what I should do.
>>>
>>> At the bottom of Glyph2's Properties Tab of the Object Inspector,
>>> change scale mode to scalar.
>>>
>>> What you will now see is not what are aiming for, it actually shows a
>>> sphere on top of every vertex within the original sets of spheres. But
>>> change the calculator filters expression and see what happens.
>>
>> Here I am a bit flying blind. Changing the numerical value in the
>> filter (1, 5, 10) does not do anything at first sight.
>> However, if I save everything to a legacy ascii vtk file, I now get
>> something large (about 30Mb).
>>
>>
>>> You should figure out why the calculator couldn't be applied to the
>>> final_config.vtk file reader's output.
>>
>> This is really the bad news. Does anyone on this list use paraview
>> from Debian testing standard repositories?
>> Actually, I should add now the problem of visualizing correctly the
>> spheres appears even in the simple example with 50 particles only;
>> there I noticed that the particles (by using radius 0.5) are actually
>> slightly smaller than they should be (and povray also disagrees).
>> I am puzzled; I thought all this would take minutes.
>> Cheers
>>
>> Lorenzo
>>
>>
>>>
>>>>
>>>> What am I doing wrong?
>>>> Regards
>>>>
>>>> Lorenzo
>>>>
>>>
>>>
>>>
>>> --
>>> David E DeMarle
>>> Kitware, Inc.
>>> R&D Engineer
>>> 28 Corporate Drive
>>> Clifton Park, NY 12065-8662
>>> Phone: 518-371-3971 x109
>>>
>>
>>
>>
>> --
>> Free will does not consist in inverting the river flow, but in being
>> the fish that leaps upstream.
>>
>
>
>
> --
> Free will does not consist in inverting the river flow, but in being
> the fish that leaps upstream.
>



-- 
David E DeMarle
Kitware, Inc.
R&D Engineer
28 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-371-3971 x109