Hi Dennis, You might also be interested in the vtkCellCenters filter. As the name suggests, it will generate the centers of the cells for you. If you are not in a big rush, I can build you a small self contained sample in Python that demonstrates the filter and the use of the point locator. I am a little busy at the moment, but I can post the sample in a couple of days.
Marco On Tue, Aug 25, 2015 at 1:40 PM, Dennis Conklin <dennis_conk...@goodyear.com > wrote: > Marco, > > > > Thanks for that tip – I’m not very familiar with vtk and I’ve never heard > of that class but it seems appropriate so I will try to dig into it. > > > > Thanks again > > > > Dennis > > > > *From:* Marco Nawijn [mailto:naw...@gmail.com] > *Sent:* Monday, August 24, 2015 10:28 AM > *To:* Dennis Conklin > *Cc:* Paraview (paraview@paraview.org) > *Subject:* [EXT] Re: [Paraview] How to find the nearest quad element? > > > > What about the following: > > > > Generate two additional datasets, one containing (an approximate of) the > center of the hex elements, the second the center of the quads. Then create > a vtkKdTreePointLocator object based on the center points of the quad > elements. Than loop over the centers of the hex elements and use one of the > Find* methods to get the closest quad. > > > > Marco > > > > > > > > > > On Fri, Aug 21, 2015 at 2:21 PM, Dennis Conklin < > dennis_conk...@goodyear.com> wrote: > > Sam, > > Thanks for responding. You have helped me several times in the past and I > am always grateful for your insights. In this case there is considerable > refinement in the model, so only a very small portion of the hex elements > are in immediate contact with quads. Also you could think of places like > the tread in the tire where there is no reinforcement whatsoever. > > Another approach which I have considered is a wave propagation technique, > where in the first wave every hex immediately adjacent to a quad gets > direction cosines assigned (as you suggest). Then you loop thru the > remaining elements and assign cosines from any adjacent quad or hex that > has cosines. Eventually the direction cosines will propagate throughout > the model. A major complication is that wavefronts will collide and then > you will have to choose which of several conflicting neighbor cosines to > adopt. Averaging is one approach but certain structures give adjoining > cosines which are 180 degrees reversed, so averaging would give you an > indeterminate direction. > > I am toying now with some pseudo-variables, such as combinations of radius > and lateral location, combined with zoning, to try to find a quantity that > is unique for a local section of the geometry, to reduce the search size > for each hex element. > > I am still hoping for a very clever scheme which someone may suggest > before I proceed with these much more brute force methods. > > Dennis > > > > *Sam Key Wrote:* > > *Dennis, * > > *Assuming for the moment that each quad 4-tuple is a finite element that > contains one or more tire reinforcement items, and that each quad 4-tuple > is "sandwiched" in between two hex 8-node finite elements, then the quad's > 4-tuple is also a surface facet of two different 8-node hexahedrons. Both > hexhedrons are the 'closest' hexhedrons to the quad. Given the usual > organization of 'element blocks' in the Exodus-II datum structures, the two > closest hexahedrons will be located on the surface of their respective > element blocks. * > > *Using material ID's which are also element block ID's, have the software > generate surface side-sets for each of these two element blocks specified > with these two material ID's. With luck, each member in the side-set will > be specified as a 2-tuple, (Elem# in the block, Quad-Face# in the hexah) * > > *With his info, you can confine your search to finding the side-set item > that has a 4-tuple that matches your quad's 4-tuple. The search is reduced > to a relatively small collection of hexahedral surface 4-tuple faces. * > > *Hope this helps. * > > *Samuel W Key FMA Development, LLC 1005 39th Ave NE Great Falls, Montana > 59404 USA * > > > > > > *From:* Dennis Conklin > *Sent:* Thursday, August 20, 2015 3:52 PM > *To:* Paraview (paraview@paraview.org) > *Subject:* How to find the nearest quad element? > > > > All, > > > > I have an Exodus, multi-block model. Most of the blocks are hex elements, > and some are layers of quads (tires are composite structures). I would > like to establish local strains which are oriented in the direction of the > nearest quad layer. To do this I need to identify, for each hex in the > model, which quad element in the model is closest to the hex. Then I can > extract directions from the quad element and rotate the strain tensor in > the hex to these local coordinates. > > > > My question is, is there some clever and efficient way to quickly > determine the nearest quad for each hex in the model. Keep in mind that > there are multiple blocks of quads, but if there is some way to address the > quad blocks one at a time, I could make this work. > > > > The brute force way is: > > Loop over every hex in the model: > > Loop over every quad in the model: > > Calculate the distance between hex and quad > > Smallest distance wins! > > > > That is a pretty brutally inefficient calc (several million hex elements) > that I am trying to avoid – any ideas about how best to approach this. > I’m hoping for some elegant way to use connectivity or something of that > sort. > > > > Thanks for looking > > > > Dennis > > > _______________________________________________ > 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 > > Search the list archives at: http://markmail.org/search/?q=ParaView > > Follow this link to subscribe/unsubscribe: > http://public.kitware.com/mailman/listinfo/paraview > > >
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