<HTML>
<HEAD>
<TITLE>Re: [Paraview] Disabling polygon offset (z-fighting prevention) in Paraview</TITLE>
</HEAD>
<BODY>
<FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>Utkarsh,<BR>
<BR>
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?<BR>
<BR>
-Ken<BR>
<BR>
<BR>
On 10/26/09 12:53 AM, "Olumide" <<a href="50295@web.de">50295@web.de</a>> wrote:<BR>
<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>Hi -<BR>
<BR>
I use Paraview not for visualizing datasets, but for inspecting<BR>
polygonal meshes and the operations I perform on them. My work involves<BR>
computing various points and line segments on meshes, and I use<BR>
VTK/Paraview to see if the points and line segments are where they ought<BR>
to be (if not, I conclude that there's a bug in my code and then proceed<BR>
to hunt it down).<BR>
<BR>
<Digression><BR>
Why I use VTK for this task: VTK is the the only publicly available 3d<BR>
graphics file format I'm aware of that explicitly supports and points,<BR>
lines, and meshes, and has a viewer for viewing these entities. Most<BR>
other 3d graphics file formats either support surfaces alone or have no<BR>
ready-made viewers.<BR>
</Digression><BR>
<BR>
Lately however, upon closer inspection, I've noticed that many of the<BR>
points and line segments that I compute appear to hover above the mesh<BR>
they are computed from and never quite touch it, and points never seem<BR>
to lie on the line segments they are supposed to. For example, see:<BR>
<a href="http://i17.photobucket.com/albums/b52/videohead/SurfaceError.png">http://i17.photobucket.com/albums/b52/videohead/SurfaceError.png</a><BR>
(note that the yellow line segment hover above the blue surface in the<BR>
horizon)<BR>
<BR>
After much experimentation, debugging and consultation, I now suspect<BR>
that this is caused by polygon offset in Paraview, designed to prevent<BR>
z-fighting. I would therefore like to know:<BR>
<BR>
(i.) if my suspicion is correct i.e. Paraview implement polygon offset<BR>
for preventing z-fighting in this case<BR>
<BR>
(ii.) if the above is true, how polygon offset can be disabled without<BR>
recompiling the source<BR>
<BR>
Thanks,<BR>
<BR>
- Olumide<BR>
<BR>
_______________________________________________<BR>
Powered by www.kitware.com<BR>
<BR>
Visit other Kitware open-source projects at <a href="http://www.kitware.com/opensource/opensource.html">http://www.kitware.com/opensource/opensource.html</a><BR>
<BR>
Please keep messages on-topic and check the ParaView Wiki at: <a href="http://paraview.org/Wiki/ParaView">http://paraview.org/Wiki/ParaView</a><BR>
<BR>
Follow this link to subscribe/unsubscribe:<BR>
<a href="http://www.paraview.org/mailman/listinfo/paraview">http://www.paraview.org/mailman/listinfo/paraview</a><BR>
<BR>
<BR>
</SPAN></FONT></BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'><BR>
</SPAN></FONT><FONT SIZE="2"><FONT FACE="Consolas, Courier New, Courier"><SPAN STYLE='font-size:10pt'><BR>
**** Kenneth Moreland<BR>
*** Sandia National Laboratories<BR>
*********** <BR>
*** *** *** email: <a href="kmorel@sandia.gov">kmorel@sandia.gov</a><BR>
** *** ** phone: (505) 844-8919<BR>
*** web: <a href="http://www.cs.unm.edu/~kmorel">http://www.cs.unm.edu/~kmorel</a><BR>
</SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'><BR>
</SPAN></FONT>
</BODY>
</HTML>