Hi Marios,
If I apply the InterpolatetoQuadraturePoints filter as shown
in Figure 2 the output result is
basically empty.
If you write the data arrays containing the scalar values at the Gauss
points to the file then you do not want to apply the "interpolate to qp"
filter. This filter's purpose is to generate these array from nodal
values. This means that you have to have the nodal values. You mentioned
that you've removed them so that you won't get confused, and that will
prevent this filter from working.
If I apply the GenerateQuadraturePoints filter as shown in Figure 3
the field data
transformed to point data. Hence after the application of the
GenerateQuadraturePoints the previous 9
point data and 4 cell data are not exist anymore but together with the
field data they transformed to 16
point data representing the 16 Gauss points. Those 16 points have the
correct coordinates and T values.
yes, that's what should happen. You're visualizing a different geometry
- the Gguass points - so data arrays on the original geometry will not
be available.
I tried to reproduce the same example using the GID software
and the results are shown in
Figure 4. Can I do something similar with Paraview? I want to have
these contour lines instead of just
point's information. I want to continue use Paraview because has some
really powerful features that I
like and I am sure this is trivial but I cannot find some way to do it.
you can't generate the contours on a point set, you first need to mesh
it. One way to do this would be to apply "delaunay 2d" to the point set.
Other approaches would be more efficient and produce better results but
would require you to write some code. eg. write out the mesh on the
Gauss points directly from your simulation.
On 12/04/2013 10:30 AM, Marios Mavros wrote:
Hi Burlen,
Thank you for your help and for your example that you have provided. I
followed your instructions and I prepare a small pdf explaining what I
did and what I expected as a final result. I thought that this
procedure was the solution to my problem but maybe I have to do
something extra or something different. Attached you will find also
the file that I used.
Thank you again for your help
Marios
On Tue, Dec 3, 2013 at 2:46 AM, Burlen Loring <[email protected]
<mailto:[email protected]>> wrote:
1. What the numbers 0 4 8 12 (line 24) represent?
This is the offset array used by VTK for random access into data
on the quadrature points data. To generate it you go cell by cell
and accumulate the number of quadrature points used by each cell.
The next cell's data offset is the sum of the previous cell's
number of quadrature points.
note that the documentation says that each array has a quadrature
scheme dictionary, but this changed. the dictionaries are stored
in the offeset array. we did this so that you only need to define
one quadrature scheme dictionary for many arrays.
2. What the QuadratureWeights are all zero (line 37)?
Those aren't currently used in VTK but we have a place holder for
them in case they are needed in user developed custom filters or
later in VTK.
3. In your example there are 4 cells with 4 Gauss points in each
cell. In total 16 Gauss points. If I want to assign to each Gauss
point one value of stress or strain how I have to write those 16
values in xml format.
in my example you would read this file into PV and apply
"interpolate to quadrature points" and then "generate quadrature
points".
You're asking about writing the data on the Gauss points into the
file. You have to store them in VTK FieldData and add an
information key to each array that names the offset array. You
have to order them correctly according to the offsets array and
quadrature scheme. for example the pdf I sent before shows how
each cell's quadrature points are ordered for one scheme. you
won't write the points themselves, just the data values.
the T FieldData array in the following file is an example of
containing scalar values at quadrature points (watch out there's
also a PointData array named T that stores the nodal values),
http://www.hpcvis.com/vis/images/vtk-quadrature-points-example/quadrature-points-example-2.vtu
after reading such a file into PV, you could see the arrays in the
spreadsheet view but to see them in the 2d/3d view you'll need to
apply the "generate quadrature points" filter to produce the point
set and transfer the data onto it.
On 12/01/2013 10:26 PM, Marios Mavros wrote:
Hi Burlen,
Your example was really helpful to understand many thing about
the xml format and I want to thank you about that, but I still
have some questions.
1. What the numbers 0 4 8 12 (line 24) represent?
2. What the QuadratureWeights are all zero (line 37)?
3. In your example there are 4 cells with 4 Gauss points in each
cell. In total 16 Gauss points. If I want to assign to each Gauss
point one value of stress or strain how I have to write those 16
values in xml format. Can you please sent me an example with this
information?
Thank you very much
Marios
On Sat, Nov 30, 2013 at 4:28 PM, Burlen Loring <[email protected]
<mailto:[email protected]>> wrote:
Hi Mario,
sending again to the list. the weights have 2 dimensions i
(node id) and j (Gauss point id), so to generate
ShapeFunctionWeights for a new QuadratureSchemeDefinition
what you do is evaluate each shape function at each Gauss
point. For the linear quadrilateral you'll end up with 16
weights. For example see the example
http://www.hpcvis.com/vis/images/vtk-quadrature-points-example/vtk-quadrature-points-example.pdf
http://www.hpcvis.com/vis/images/vtk-quadrature-points-example/quadrature-points-example.vtu
Burlen
On 11/29/2013 3:34 PM, Marios Mavros wrote:
Hi Burlen,
I want to thank you for the information that you send me. I
read the paper and I try to made a simple example in xml
format for a 4 node quadrilateral element but it didn't work
for me. Attached you will find the element formulation that
I used with the shape functions and a .vtu file with my
example. If I want to give 4 stress values in the 4 Gauss
points ( lets say 0.1 0.2 0.4 -0.1) can you please write in
the .vtu file the missing information in order to understand
haw I have to write a correct file in xml format.
Thank you very much
Marios Mavros
On Wed, Nov 27, 2013 at 2:56 PM, Burlen Loring
<[email protected] <mailto:[email protected]>> wrote:
You'll need to use an XML file format. There's some
documentation in the following link. It's slightly dated
but should get you started.
http://www.vtk.org/Wiki/images/7/78/VTK-Quadrature-Point-Design-Doc.pdf
The ctest,
VTK/Filters/General/Testing/Cxx/TestQuadraturePoints.cxx, could
be used as an example.
On 11/27/2013 02:32 PM, Marios Mavros wrote:
Hi
I have wrote a simple program in Fortran that transform
the output of a finite element software in vtk Legacy
Format. I don't know how to handle the Gauss points
values. For example in my case my cells have 4 Gauss
points and I have 4 values (for example strain in
x-direction) for each cell. How I have to write the vtk
file taking into account that each cell has many Gauss
points?
Thank you
Marios
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