[vtkusers] Near plane clipping problem

[Gerrick Bivins]

I'm running into this problem and thought it may have been something with my
setup but your patches fixed my issues!
Did these ever get accepted into vtk? I'm still using 5.2 at the moment.
Gerrick

On Fri, Oct 17, 2008 at 11:43 AM, Serge Lalonde <serge at infolytica.com>wrote:

>  Hi Ben,
>
> No, I haven't seen these artifacts yet. However, I am still in the
> prototyping stage and my models are pretty simple (a cube made up of 5
> tetrahedra and a vtkConeSource). I'll let you know if I run into this when I
> move on to some real models.
>
> Thanks.
>
> Ben Held wrote:
>
> Serge,
>
> We have been having trouble with this as well and implemented something
> similar to what you did and found that if the near clipping plane value gets
> too small one starts to see strange visual artifacts (shading, lighting,
> etc).  Have you noticed any such problems?
>
> Ben
>
> -----Original Message-----
> From: vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org <vtkusers-bounces at vtk.org>] On Behalf
> Of Serge Lalonde
> Sent: Friday, October 17, 2008 10:10 AM
> To: VTK Users
> Subject: [vtkusers] Near plane clipping problem
>
> Has anyone ever noticed that it is very easy to cause the near clipping
> plane to cut-off the model when in parallel projection mode?
>
> I ran into this recently when adding a vtkBoxWidget and scaling a simple
> cube a few times after rotating it so that one of the corners points towards
> the viewer.
>
> I tried calling vtkRenderer::ResetCameraClippingRange() to no avail.
> vtkRenderer::ResetCamera() fixed the problem, but would lose my camera
> setting.
>
> After searching fruitlessly in the vtkusers archives, I decided to trace
> into the code and I discovered that there is code in
> vtkRenderer::ResetCameraClippingRange() and
> vtkCamera::SetClippingRange() that modifies the near plane value to "fix"
> potential camera and depth buffer problems. In my opinion, these fixes are
> valid, but only for perspective projections. For parallel projections, they
> are unnecessary and in fact cause the clipping problem I was encountering.
> To test this, I modified the code and rebuilt and lo and behold, no more
> near plane clipping!
>
> I decided to document this in the vtkusers list in case others have run into
> this problem. Attached is my modified version of vtkCamera.cxx and
> vtkRenderer.cxx along with the patch files relative to version 5.2.0 (only
> vtkCamera.cxx has changed since then). The changes are small and localized.
> If anyone tries them, let me know if you run into any problems (or even if
> you don't). I will submit them to Kitware for consideration also.
>
> Thanks.
>
>
>
>
>
> --
> www.infolytica.com
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>
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