[vtkusers] vtkCutter leaves "gaps"

[David Gobbi]

A "Tesselator" filter, I think?


On Mon, Dec 9, 2013 at 9:43 AM, Gerrick Bivins <
Gerrick.Bivins at halliburton.com> wrote:

>  Ok. I tried to  “Tetrahedralize” the dataset before using the cutter,
> and it produced
>
> a “gapless” slice in paraview.
>
> It loses the structure of the cells (everything is triangles obviously)
> but at least it doesn’t drop elements.
>
>
>
> What filter does “Tetrahedralize” map to in VTK?
>
>
>
> Gerrick
>
> *From:* David Gobbi [mailto:david.gobbi at gmail.com]
> *Sent:* Friday, December 06, 2013 2:01 PM
>
> *To:* Gerrick Bivins
> *Cc:* Bill Lorensen; vtkusers at vtk.org
> *Subject:* Re: [vtkusers] vtkCutter leaves "gaps"
>
>
>
> Hi Gerrick,
>
>
>
> If it's polyhedral cells, then yes, a bug is a definite possibility.
>  Gathering info from other poly users is the right way to go.  Sorry that I
> can't be of more help, but I haven't used poly cells myself.
>
>
>
>   David
>
>
>
> On Fri, Dec 6, 2013 at 12:47 PM, Gerrick Bivins <
> Gerrick.Bivins at halliburton.com> wrote:
>
> Bill,
>
> For some reason it took a couple of tries to get that one through. Maybe
> attachement size was too big but it made it to the nabble list:
>
>
> http://vtk.1045678.n5.nabble.com/vtkCutter-leaves-quot-gaps-quot-tt5724617.html
>
>
>
> David,
>
> Right, it feels like a bug in polyhedron cells.
>
> My data was pretty simple, a block with poly cells a with varying
> thickness and width.
>
> Definitely no holes. I probably can’t send it along but
>
> note there was just recently a post (probably minutes before my “BUMP”
> made it through) about a very similar issue:
>
>
> http://vtk.1045678.n5.nabble.com/Bug-in-slice-and-clip-for-mesh-containing-VTK-POLYHEDRON-cells-tt5724879.html
>
> It also has a problematic model attached.
>
>
>
> Gerrick
>
>
>
>
>
> *From:* David Gobbi [mailto:david.gobbi at gmail.com]
> *Sent:* Friday, December 06, 2013 12:42 PM
> *To:* Gerrick Bivins
> *Cc:* Bill Lorensen; vtkusers at vtk.org
> *Subject:* Re: [vtkusers] vtkCutter leaves "gaps"
>
>
>
> Hi Gerrick,
>
>
>
> The cutter algorithm is fairly straightforward, it just creates a new
> point along each edge that is intersected by the plane.  Then it uses its
> knowledge about the connectivity of the original cells to join the new
> points together to create new cells.
>
>
>
> The only problem I've ever seen with vtkCutter is the fact that its
> locator is limited by numerical precision: it might think two cells share
> an edge when in fact the edges are just very, very close to each other.
>  But the result of this is that gaps are closed, not created.
>
>
>
> In response to the question about whether I've ever seen vtkCutter create
> gaps where no gaps exist in the original data, I'd have to say no.  That's
> not to say that it could never happen.  The vtkCutter delegates the
> "cutting" to the Contour methods of the various cell classes, so it is
> possible that your data uses a cell type with a buggy Contour
> implementation.  If that is the case, it would be good to know the details
> of your data so that someone can investigate, but my first suspicion is
> that the gaps are present in your original data.
>
>
>
>   David
>
>
>
> On Fri, Dec 6, 2013 at 11:13 AM, Bill Lorensen <bill.lorensen at gmail.com>
> wrote:
>
> I do not see the attachment/
>
>
>
> On Fri, Dec 6, 2013 at 12:50 PM, Gerrick Bivins <
> Gerrick.Bivins at halliburton.com> wrote:
>
>   I realized I sent this at a time when most people were probably offline.
>
> Just a “BUMP” in case this got missed.
>
> Anyone have any ideas here?
>
> Gerrick
>
> *From:* vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] *On
> Behalf Of *Gerrick Bivins
> *Sent:* Monday, November 25, 2013 8:33 AM
> *To:* 'vtkusers at vtk.org'
> *Subject:* [vtkusers] vtkCutter leaves "gaps"
>
>
>
> Hi All,
>
> I’ve run into a strange problem where with some of my datasets, vtkCutter
> is leaving “gaps” in the output polydata.
>
> For example, if I use a plane as the implicit function the attached image
> shows the result.
>
> Anyone seen this kind of  behavior before?
>
> Is there some setting on the vtkCutter that is perhaps causing this?
>
>
>
> Gerrick
>
>
>
>
>
>
>
> [image: DecisionSpace® 5000.8.3 Now Available]<https://www.landmarksoftware.com/Pages/Geosciences.aspx>
>
>
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