Cory, So indeed there has to be a normal *per point and per face*, and not *per face*? And, likewise, points are not shared between adjacent faces. I had overlooked that detail in the documentation, tacitly assuming that "of course" the normals are *per face*.
Regards, Bertwim On 10/11/2014 04:48 PM, Cory Quammen wrote: > Bertwim, > > You are right that there is a redundancy in points. That stems from > the need for defining different normals at the corner points for each > face. In theory, you could define more than one normal for the same > point and associate it with a face, but that complicates the data > structure. It is much simpler to duplicate points and associate > exactly one normal per point. > > In most polygonal data, you won't see duplicated points at most > places. But for anything that should be displayed with a sharp edge, > duplicate points will be present. > > - Cory > > On Sat, Oct 11, 2014 at 10:23 AM, B.W.H. van Beest <[email protected]> wrote: >> Hi, >> >> When I look into the source code of vtkCubeSource.cpp, >> I noticed that, although a (rectangular) 3D box can be described by >> 8 3D points and 6 2D faces (hence also 6 3D normal vectors), >> in the actual code of vtkCubeBoxSource:RequestData() there are 24 3D >> points generated, >> with for every point a normal (???), and indeed 6 faces (polys). >> Why is there this redundancy? >> >> I bumped on this when I applied the "HiddenLineRemoval" representation to >> my own handcrafted box (with 8 points, 6 faces and 6 normals). It yielded >> an incorrect view whereas the box with the redundant numbers of data >> gave the correct one. But I don't get the logic. >> >> Regards, >> Bertwim >> _______________________________________________ >> 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://public.kitware.com/mailman/listinfo/paraview > _______________________________________________ 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://public.kitware.com/mailman/listinfo/paraview
