Hi Jie, Renato, There had been a bug until ParaView 3.4 that led the volume of a wedge to have been miscalculated as a negated volume of a tetrahedron. http://www.paraview.org/pipermail/paraview/2008-August/009246.html http://paraview.org/Bug/view.php?id=7588
The bug has been fixed with the recent CVS versions. I can confirm that the bug also affects volume calculations of clipped hexahedral meshes as well by Jie's test.vtk. If I try the .vtk with a CVS version and follow Jie's procedure I get a volume of 4.95177e-13 which is closer to the analytic value of 5.23599e-13. However if I revert the bugfix (revert vtkWedge.cxx from the current revision 1.7 to ParaView 3.4's 1.5) I get the identical value with what Jie got, 3.32862e-13. Takuya OSHIMA, Ph.D. Faculty of Engineering, Niigata University 8050 Ikarashi-Ninocho, Nishi-ku, Niigata, 950-2181, JAPAN From: Renato Elias <[email protected]> Subject: Re: [Paraview] Questions regarding: volume calculation, xyplot along a curve and tensor calculation Date: Fri, 10 Apr 2009 22:39:36 -0300 > It seems rounding errors... try to scale your model at least 100x to see > what happens... > > Just to reforce Jie Xu's problem. It's not the first time the Integrate > Variable presents issues in volume calculations. Take a look: > http://markmail.org/message/67dkxpypfodylfnr#query:volume%20integration%20paraview%20renato+page:1+mid:67dkxpypfodylfnr+state:results > > In my case, I don't remember if the problem was solved.... > > I tried to find my dataset to test it again but I haven't found (yet).... > :-( > > Renato. > > > > On Fri, Apr 10, 2009 at 4:30 PM, Jie Xu <[email protected]> wrote: > >> Hi Berk, >> >> Thanks for looking at my questions. >> >> 1) I attached a sample data set: test.vtk, and the screenshot of my >> paraview window, from which you can see that the clip is created at >> (0,0,0) with radius of 50e-6, and the calculated volume is >> 3.32862e-13, which is much less than what it should be. >> (Interestingly, in this specific case, the calculated volume is about >> 2/pi times the real volume.) >> >> 2) Thanks for letting me know. >> >> 3) Unfortunately, I have no experience with Python. Now I am trying to >> see if I can use matlab to do the tensor calculates and modify the vtk >> file readable by paraview. >> >> Regards, >> Jie >> >> On Thu, Apr 9, 2009 at 1:51 PM, Berk Geveci <[email protected]> >> wrote: >> > Hi Jie, >> > >> >> 1) Volume calculation: >> >> I found that the "integrate variables" over a sphere clip never gives >> >> the correct volume. For example, I tried to use a very simple geometry >> >> and a very fine mesh (a 200x200x200 micron cube with 2 micron cube >> >> elements), and use paraview to generate a sphere clip that has radius >> >> of 50 micron in the center of that cube, then I apply the "integrate >> >> variables" filter to the clip and show the "Cell Data", it gives a >> >> volume of 4.78818e-13 instead of 5.236e-13, which is 4/3*pi*r^3. The >> >> discrepancy is so large that it just cannot be due to the coarseness >> >> of the mesh. Different mesh and different size of clips gives >> >> different discrepancies, and I cannot find any obvious relationship >> >> between the paraview-calculated volume and the real volume. >> > >> > When I create a 100^3 wavelet and clip it with a sphere of radius 20, >> > I am getting a volume of 33447.5 which is pretty close to the analytic >> > value of 33510.3. Can you send me a dataset that demonstrates this >> > problem? >> > >> >> 2) X-Y plot: how can I do a xyplot of a scalar along a curved line? >> >> For example, if I have the pressure field data from a >> >> flow-around-a-cylinder case, I want to plot the pressure along the >> >> surface of the cylinder as a function of angle or arc length. >> > >> > You can't, yet. I am working on that feature for the next release. >> > >> >> 3) tensor calculation: I have the pressure field and velocity field >> >> calculated from a CFD tool (Transat in my case), how do I calculate >> >> stress tensors at each point from P V field in paraview? >> > >> > Let me ask a question back : do you have any Python knowledge? We are >> > working on making this really simple but currently the array >> > calculator is too limited and cannot produce tensors. However, this is >> > doable using the programmable filter. >> > >> > -berk _______________________________________________ Powered by www.kitware.com Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Please keep messages on-topic and check the ParaView Wiki at: http://paraview.org/Wiki/ParaView Follow this link to subscribe/unsubscribe: http://www.paraview.org/mailman/listinfo/paraview
