Ken, Offsetting the points/lines handles the cases when people try to render two overlapping datasets: one as surface and other as wireframe, and they don't necessarily want to show surface with edges (say they want scalar coloring for both surface and the wireframe). I believe Jean Favre has several such use cases.
Utkarsh On Mon, Oct 26, 2009 at 1:18 PM, Moreland, Kenneth <[email protected]> wrote: > Utkarsh, > > After reading this question from Olumide, I noticed that ParaView now turns > on ZShift for lines and points (vtkProcessModule.cxx, 198-199). I don’t > know why this is. This effect is turned off when drawing surface+edges > (vtkOpenGLCoincidentTopologyResolutionPainter.cxx, 56-58) because it > automatically switches to offsetting the polygons the polygons back > (vtkOpenGLRepresentationPainter.cxx, 79-85). Should we remove those two > lines from vtkProcessModule.cxx? > > -Ken > > > On 10/26/09 12:53 AM, "Olumide" <[email protected]> wrote: > > Hi - > > I use Paraview not for visualizing datasets, but for inspecting > polygonal meshes and the operations I perform on them. My work involves > computing various points and line segments on meshes, and I use > VTK/Paraview to see if the points and line segments are where they ought > to be (if not, I conclude that there's a bug in my code and then proceed > to hunt it down). > > <Digression> > Why I use VTK for this task: VTK is the the only publicly available 3d > graphics file format I'm aware of that explicitly supports and points, > lines, and meshes, and has a viewer for viewing these entities. Most > other 3d graphics file formats either support surfaces alone or have no > ready-made viewers. > </Digression> > > Lately however, upon closer inspection, I've noticed that many of the > points and line segments that I compute appear to hover above the mesh > they are computed from and never quite touch it, and points never seem > to lie on the line segments they are supposed to. For example, see: > http://i17.photobucket.com/albums/b52/videohead/SurfaceError.png > (note that the yellow line segment hover above the blue surface in the > horizon) > > After much experimentation, debugging and consultation, I now suspect > that this is caused by polygon offset in Paraview, designed to prevent > z-fighting. I would therefore like to know: > > (i.) if my suspicion is correct i.e. Paraview implement polygon offset > for preventing z-fighting in this case > > (ii.) if the above is true, how polygon offset can be disabled without > recompiling the source > > Thanks, > > - Olumide > > _______________________________________________ > 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 > > > > > **** Kenneth Moreland > *** Sandia National Laboratories > *********** > *** *** *** email: [email protected] > ** *** ** phone: (505) 844-8919 > *** web: http://www.cs.unm.edu/~kmorel > > _______________________________________________ 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
