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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Thanks guys for the feedback. I have
attached two images to visualize what follows. I hope I can explain this
clearly.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I have three renderers that I am adding to
the render window.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The first is to contain a textured vtkGlobeSource
actor and is called the background renderer.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The second contains several vtkPolyData
actors and are lines (State and county boundaries, roads, rivers…), this
is called the map renderer.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The Third contains an actor visualizing a weather
radar volume, this is called the radar renderer.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The background renderer is always set as
layer 0 and so is always rendered first.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The map renderer and radar renderer will
alternate between the 1<sup>st</sup> and 2<sup>nd</sup> layers depending on the
view angle of the camera.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>If the camera is more than 45 degrees
above the horizon then the radar renderer is layer 1 and the map renderer is
layer 2 so that the user can see the features below the radar volume.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>If the camera is less than or equal to 45
degrees above the horizon then the map renderer is layer 1 and the radar renderer
is layer 2 so that the radar volume is always in front of the map features.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>This works fine until I draw all state
lines for the entire US. Because the vtkGlobeSource simulates the curvature of
the earth I see the backside of the state lines where they are over the view
horizon.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Is there a way I can put the map features
and radar volume on the same renderer and accomplish the same thing?</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Thanks.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'>-----Original Message-----<br>
<b><span style='font-weight:bold'>From:</span></b> Aashish Chaudhary [mailto:aashish.chaudhary@kitware.com]
<br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, November 18, 2010
8:37 AM<br>
<b><span style='font-weight:bold'>To:</span></b> David Gobbi<br>
<b><span style='font-weight:bold'>Cc:</span></b> vtkusers@vtk.org; Donny<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [vtkusers] How to use
backface culling with polylines</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Donny, </span></font></p>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Were you talking about hidden lines removal may
be? </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Thanks, </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>On Thu, Nov 18, 2010 at 9:03 AM, David Gobbi <<a
href="mailto:david.gobbi@gmail.com">david.gobbi@gmail.com</a>> wrote:</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Jerome is correct, OpenGL culls faces according to the
polygon<br>
winding. So wireframe polygons can be culled, but polylines cannot,<br>
even if they have normals assigned to them. There are some details in<br>
the OpenGL FAQ:<br>
<a href="http://www.opengl.org/resources/faq/technical/clipping.htm"
target="_blank">http://www.opengl.org/resources/faq/technical/clipping.htm</a><br>
<font color="#888888"><span style='color:#888888'><br>
David</span></font></span></font></p>
<div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><br>
On Wed, Nov 17, 2010 at 11:47 PM, Jérôme <<a
href="mailto:jerome.velut@gmail.com">jerome.velut@gmail.com</a>> wrote:<br>
> Hi Donny,<br>
><br>
> My feeling is that backface culling should not work with polylines because
they<br>
> have actually no face.<br>
><br>
> Jerome<br>
><br>
> 2010/11/18 Donny <<a href="mailto:donnyz@charter.net">donnyz@charter.net</a>>:<br>
>> I am drawing polylines using vtkPolyData and cannot get backface
culling to<br>
>> work with them.<br>
>><br>
>><br>
>><br>
>> I ran into this subject<br>
>> <a
href="http://public.kitware.com/pipermail/vtkusers/2003-January/065023.html"
target="_blank">http://public.kitware.com/pipermail/vtkusers/2003-January/065023.html</a>
, but<br>
>> did not help.<br>
>><br>
>><br>
>><br>
>> Any solutions?<br>
>><br>
>><br>
>><br>
>> Donny Zimmerman<br>
>><br>
>> <a href="mailto:donnyz@charter.net">donnyz@charter.net</a><br>
>><br>
>> 308-227-1756<br>
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<br clear=all>
<br>
-- <br>
| Aashish Chaudhary <br>
| R&D Engineer <br>
| Kitware Inc. <br>
| <a href="http://www.kitware.com">www.kitware.com</a> </span></font></p>
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