[vtkusers] Rendering of vtkGPUVolumeRayCastMapper with AddClippingPlane

[David Gobbi]

Hi Tijmen,

You should submit a bug report for this, otherwise it will just get
lost on the mailing list:
http://www.vtk.org/Bug/view_all_bug_page.php

I've seen similar problems with the vtkGPUVolumeRayCastMapper
but never took the time to analyze them.  For me, the issue was that
the rendering was incorrect if the clipping planes were used together
with a cropping region.  Your issue, where the rendering is different
depending on whether an actor transform is used versus whether a
camera transform is used, produces the same sort of rendering
artifacts that I was seeing i.e. huge chunks of the volume are
missing.

 - David


On Mon, Jul 18, 2011 at 6:03 AM, Tijmen Klein <T.R.Klein at student.rug.nl> wrote:
> I am using a vtkGPUVolumeRayCastMapper to render a structured grid, with the
> use of AddClippingPlane member (of vtkGPUVolumeRayCastMapper). Now, I'm
> getting some weird rendering behavior that depends on the interactor that is
> used:
> vtkInteractorStyleTrackballActor:  Rendering sometimes looks good, but most
> of the time weird rendering artifacts show when doing this. This is how it
> should look: http://dl.dropbox.com/u/27566470/good.png, but most of the time
> it looks like something like this: http://dl.dropbox.com/u/27566470/bad.png
> or http://dl.dropbox.com/u/27566470/bad2.png These artifacts change based on
> the rotation that is applied with the interactor.
> vtkInteractorStyleTrackballCamera:  When I start with this interactor, the
> clipping is not applied at all. I just see the normal volume (without
> rendering artifacts). If I start with the Actor Interactor (and try to get a
> view without artifacts), and then switch to the Camera Interactor: then
> everything seems to be working fine. The view stays clipped, and no
> artifacts occur. But I can not get it to work with just the Camera
> Interactor. However, I would prefer to use the Actor Interactor for my
> interactions, so switching to Camera mode is not really wanted.
> Are this known issues? What am I doing wrong that the clipping is not
> happening in Camera mode? And is there a way to prevent the artifacts?
>
> Tijmen