[vtkusers] PolyData rendering problem

Thu Nov 14 11:34:28 EST 2013

Thank you.

From: vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] On Behalf
Of Aashish Chaudhary
Sent: Thursday, November 14, 2013 4:23 AM
To: Frank Gao
Cc: VTK Users
Subject: Re: [vtkusers] PolyData rendering problem

On Thu, Nov 14, 2013 at 1:01 AM, Frank Gao <Frank.Gao at guidemia.com
<mailto:Frank.Gao at guidemia.com> > wrote:

Hi Aashish, David,

I found out some old posting, and got a clue that the code can be
RenderWindow()->SetPolygonSmoothing() and RenderWindow()->SetMultiSamples().
Did some test and found out they can not be used together. Only
SetMultiSamples() will solve the problem. I tried SetMultiSamples(8) and
SetMultiSamples(2). Both worked fine. I have no idea which one we should
use, and what's the impact.

Don't use polygon smoothing that's the old way
(http://www.gamedev.net/topic/107637-glenablegl_polygon_smooth/) 

Can you please confirm this is the right thing to do? And what number should
we use in SetMultiSamples?

I believe VTK does this (http://www.opengl.org/wiki/Multisampling) the more
samples you have the poorer the performance you will get.  However, if your
data is not that big, then I would suggest set it to 8 if not then 4 should
be good enough. 

Best regards,

Frank

From: vtkusers-bounces at vtk.org <mailto:vtkusers-bounces at vtk.org>
[mailto:vtkusers-bounces at vtk.org <mailto:vtkusers-bounces at vtk.org> ] On
Behalf Of Frank Gao
Sent: Wednesday, November 13, 2013 9:06 PM
To: 'Aashish Chaudhary'

Cc: 'VTK Users'
Subject: Re: [vtkusers] PolyData rendering problem

Hi Aashish, David,

Yes it is confirmed that the Antialiasing option is the reason. With either
preference setting, when this one is off, we will see the problem. Setting
antialiasing by 2x or 4x does not make noticeable difference. So my guess is
that setting the Antialiasing will fix the problem, but we are not sure
where and how is the best fix. Could you please shed some lights on this? 

Please see the following for a sample model. 

https://www.dropbox.com/s/f4dnywwcohlrvko/polydata_rendering_case.stl

Best regards,

Frank

From: vtkusers-bounces at vtk.org <mailto:vtkusers-bounces at vtk.org>
[mailto:vtkusers-bounces at vtk.org] On Behalf Of Aashish Chaudhary
Sent: Wednesday, November 13, 2013 6:01 AM
To: Frank Gao
Cc: VTK Users
Subject: Re: [vtkusers] PolyData rendering problem

Can you try this experiment: 

Keep the setting to performance but just turn on the Antialiasing if it is
possible to change that setting individually? There you will find options as
well. Try different options and let us know if you see the difference? 

It could be either: z buffer precison issue or antialiasing issue if there
is nothing special about your dataset. 

Also, can you send us this dataset?

- Aashish

On Tue, Nov 12, 2013 at 11:57 PM, Frank Gao <Frank.Gao at guidemia.com
<mailto:Frank.Gao at guidemia.com> > wrote:

Hi David,

I did a comparison between the nVidia card settings, and found out the
differences with "Performance" and "Quality" preference. Please see the
document below. 

https://www.dropbox.com/s/vwdgj44zz6y3w6w/nVIdiaCard_Setting_difference.docx

I am assuming there are some OpenGL calls to implement the difference, but
don't really know what to do. Hope this can provide some clues.

Best regards,

Frank

From: vtkusers-bounces at vtk.org <mailto:vtkusers-bounces at vtk.org>
[mailto:vtkusers-bounces at vtk.org <mailto:vtkusers-bounces at vtk.org> ] On
Behalf Of David E DeMarle
Sent: Tuesday, November 12, 2013 4:43 PM
To: Frank.Gao at guidemia.com <mailto:Frank.Gao at guidemia.com> 
Cc: VTK Developers; VTK Users
Subject: Re: [vtkusers] PolyData rendering problem

What is the world space size of the triangles? Are they small enough to push
the limits of GL float precision?

David E DeMarle
Kitware, Inc.
R&D Engineer
21 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-881-4909 <tel:518-881-4909> 

On Tue, Nov 12, 2013 at 6:10 PM, Frank Gao <Frank.Gao at guidemia.com
<mailto:Frank.Gao at guidemia.com> > wrote:

Hi All,

We are having some problems with the surface rendering in VTK. If the users
don't set their graphics card preference to "Quality", the surface rendering
will show a lot of "ghost" lines between the triangles, but they are not the
polydata edges. Completely display artifact. When the triangles are small,
this is much more obvious. I places a picture in the following link. The
left one has problem. The right one is when preference is set to "quality".

https://www.dropbox.com/s/1kvpzia57uggist/vtk_polydata_rendering_case.PNG

Because of this we have to tell the users to change their graphics card
setting. Is this something we can do in the code? Thanks a lot in advance.

Regards,

Frank Gao

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-- 
| Aashish Chaudhary 
| R&D Engineer         
| Kitware Inc.            
| www.kitware.com <http://www.kitware.com>     

-- 
| Aashish Chaudhary 
| R&D Engineer         
| Kitware Inc.            
| www.kitware.com <http://www.kitware.com>     

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