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face culling and edge visibility

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face culling and edge visibility

Miroslav Drahos-2

Hi VTK folks,

I am rendering a surface with culling faces on and edge visibility on as well. When I used VTK 6.2, only the edges of faces that were visible (i.e. not culled) were shown, with VTK 7.1.0 all edges are visible, even for faces that are culled. My VTK 6.2 was compiled with rendering backend OPENGL, and 7.1.0 with OPENGL2, which is what most likely causes the difference in behavior.

It does not matter whether front or back face culling is used, the edge visibility behavior is the same.


What I am hoping to hear: Is there a way to get the "old" behavior with VTK7.1/OPENGL2?

I would like to show the edges only for the faces that are not culled away.


Thank you tons,

Miro





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Re: face culling and edge visibility

Ken Martin
Unfortunately wireframe backface culling is not implemented. But maybe hidden line removal would do the job or maybe even better. See




On Fri, Mar 24, 2017 at 8:14 PM, Miroslav Drahos <[hidden email]> wrote:

Hi VTK folks,

I am rendering a surface with culling faces on and edge visibility on as well. When I used VTK 6.2, only the edges of faces that were visible (i.e. not culled) were shown, with VTK 7.1.0 all edges are visible, even for faces that are culled. My VTK 6.2 was compiled with rendering backend OPENGL, and 7.1.0 with OPENGL2, which is what most likely causes the difference in behavior.

It does not matter whether front or back face culling is used, the edge visibility behavior is the same.


What I am hoping to hear: Is there a way to get the "old" behavior with VTK7.1/OPENGL2?

I would like to show the edges only for the faces that are not culled away.


Thank you tons,

Miro





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--
Ken Martin PhD
Distinguished Engineer
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065

This communication, including all attachments, contains confidential and legally privileged information, and it is intended only for the use of the addressee.  Access to this email by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken in reliance on it is prohibited and may be unlawful. If you received this communication in error please notify us immediately and destroy the original message.  Thank you.

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Re: face culling and edge visibility

Miroslav Drahos-2

Thank you for the response and the link; I looked at hidden line removal, it's a very cool feature. Unfortunately, it does not solve my problem, because I use front face culling:

I render the mesh as fully opaque surface representation (not wireframe). Then I cull front faces away, so that I can see objects inside the mesh unobstructed; at the same time, the mesh is opaque, so it obstructs object behind it.


Software is for medical application, visualizing navigation path inside anatomy -- I want to show path unobstructed, and hide everything behind the anatomy surface model.


Attaching a couple images of what it looks like in 6.2 with OPENGL backend (i.e. what I want it to look like). ffCullDesired1 is the view user will get; in ffCullDesired2 I rotated camera to illustrate what's happening. With VTK7.1+OPENGL2 I get the edges obstructing the path.


One obvious workaround for me would be to turn edge visibility off, and render polygons in color, but I the design has been finalized and I don't have much control over it, I'm just implementing it.


Any other suggestions are most appreciated!

Thank you,

Miro



From: Ken Martin <[hidden email]>
Sent: Saturday, March 25, 2017 2:18:52 PM
To: Miroslav Drahos
Cc: [hidden email]
Subject: Re: [vtkusers] face culling and edge visibility
 
Unfortunately wireframe backface culling is not implemented. But maybe hidden line removal would do the job or maybe even better. See

https://blog.kitware.com/hidden-line-removal-now-available-in-vtk-and-paraview/




On Fri, Mar 24, 2017 at 8:14 PM, Miroslav Drahos <[hidden email]> wrote:

Hi VTK folks,

I am rendering a surface with culling faces on and edge visibility on as well. When I used VTK 6.2, only the edges of faces that were visible (i.e. not culled) were shown, with VTK 7.1.0 all edges are visible, even for faces that are culled. My VTK 6.2 was compiled with rendering backend OPENGL, and 7.1.0 with OPENGL2, which is what most likely causes the difference in behavior.

It does not matter whether front or back face culling is used, the edge visibility behavior is the same.


What I am hoping to hear: Is there a way to get the "old" behavior with VTK7.1/OPENGL2?

I would like to show the edges only for the faces that are not culled away.


Thank you tons,

Miro





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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 VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ

Search the list archives at: http://markmail.org/search/?q=vtkusers

Follow this link to subscribe/unsubscribe:
http://public.kitware.com/mailman/listinfo/vtkusers




--
Ken Martin PhD
Distinguished Engineer
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065

This communication, including all attachments, contains confidential and legally privileged information, and it is intended only for the use of the addressee.  Access to this email by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken in reliance on it is prohibited and may be unlawful. If you received this communication in error please notify us immediately and destroy the original message.  Thank you.

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ffCullDesired1.png (535K) Download Attachment
ffCullDesired2.png (694K) Download Attachment
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