[vtkusers] Make Smooth Isosurfaces

[Bill Lorensen]

If the outside of your mesh is a "box", that is all you will see.

I'll take a look.

Bill

On Fri, Oct 30, 2009 at 12:27 PM, Sanket Jain <jainsanket1 at gmail.com> wrote:
> When I open the unstructured grid file in paraview, I get a opaque border of
> my geometry. When I decrease the opacity, I just see a hollow box. I cannot
> see my mesh inside the box. I think there is some problem with the file. But
> I compared my file with the format for writing unstructured grid and it
> looks correct to me. Do you mind having a look at the file (attached)? I
> know this might be asking for too much help. I really appreciate your
> efforts to help me.
>
> Sanket
>
> On Fri, Oct 30, 2009 at 11:17 AM, Bill Lorensen <bill.lorensen at gmail.com>
> wrote:
>>
>> I mean the unstructured grid (the geometry).
>>
>> On Fri, Oct 30, 2009 at 12:10 PM, Sanket Jain <jainsanket1 at gmail.com>
>> wrote:
>> > Ok. I will recheck my matlab program which writes the vtk file and get
>> > back
>> > to you.
>> >
>> > For Paraview, did you mean only the mesh points without the scalar
>> > values? I
>> > checked the unstructured grid with scalars on them. They look exactly
>> > the
>> > same as in my VTK code.
>> >
>> > Sanket
>> >
>> > On Fri, Oct 30, 2009 at 7:55 AM, Bill Lorensen <bill.lorensen at gmail.com>
>> > wrote:
>> >>
>> >> Perhaps your scalar values are not associated with the proper points?
>> >> Have you looked at the original unstructured grid with paraview?
>> >>
>> >> On Thu, Oct 29, 2009 at 10:21 PM, Sanket Jain <jainsanket1 at gmail.com>
>> >> wrote:
>> >> > Yes, I tried for number of isovalues. But all of them have similar
>> >> > characteristics. Is it anything to do with the vtk file being in
>> >> > unstructured grid rather than polygonal data? For the mesh, I
>> >> > imported
>> >> > from
>> >> > COMSOL, I cannot use polygonal data.
>> >> >
>> >> > Sanket Jain
>> >> > On Thu, Oct 29, 2009 at 6:33 PM, Bill Lorensen
>> >> > <bill.lorensen at gmail.com>
>> >> > wrote:
>> >> >>
>> >> >> It does look strange. Have you tried changing the isosurface value?
>> >> >>
>> >> >> On Thu, Oct 29, 2009 at 5:44 PM, Sanket Jain <jainsanket1 at gmail.com>
>> >> >> wrote:
>> >> >> > I have attached a snapshot of my viewer. The isosurface is
>> >> >> > predicting
>> >> >> > the
>> >> >> > volume activated during monopolar stimulation. So, theoretically
>> >> >> > you
>> >> >> > will
>> >> >> > expect a sphere at a particular iso value.
>> >> >> >
>> >> >> > I tried using vtkPolyDataNormals. The figure attached is the
>> >> >> > output
>> >> >> > after
>> >> >> > including this filter. But I still think this is not smooth.
>> >> >> >
>> >> >> > I verified by opening my vtk file in Paraview (with, Compute
>> >> >> > Normal
>> >> >> > ON).
>> >> >> > Even then i get the same kind of response. So, do you think this
>> >> >> > is
>> >> >> > the
>> >> >> > best
>> >> >> > i can get? Or there might be some problem in the vtk file which is
>> >> >> > exported
>> >> >> > from COMSOL (I verified it multiple times).
>> >> >> >
>> >> >> > Thank you,
>> >> >> >
>> >> >> > Sanket
>> >> >> >
>> >> >> > On Thu, Oct 29, 2009 at 4:01 PM, Bill Lorensen
>> >> >> > <bill.lorensen at gmail.com>
>> >> >> > wrote:
>> >> >> >>
>> >> >> >> Sorry, reading your e-mail in more detail. Are you generating the
>> >> >> >> isosurfaces in vtk using vtkContourFIiter or some equivalent. If
>> >> >> >> so,
>> >> >> >> you should run the output through vtkPolyDataNormals.
>> >> >> >>
>> >> >> >> On Thu, Oct 29, 2009 at 4:59 PM, Bill Lorensen
>> >> >> >> <bill.lorensen at gmail.com>
>> >> >> >> wrote:
>> >> >> >> > What do you mean by rough? Perhaps the faces are flat shaded?
>> >> >> >> > How
>> >> >> >> > are
>> >> >> >> > you displaying the model in vtk?
>> >> >> >> >
>> >> >> >> > Are your isosurfaces composed of only triangles? If so, did you
>> >> >> >> > provide surface normals at each point?
>> >> >> >> >
>> >> >> >> > On Thu, Oct 29, 2009 at 4:30 PM, Sanket Jain
>> >> >> >> > <jainsanket1 at gmail.com>
>> >> >> >> > wrote:
>> >> >> >> >> Hello Experts,
>> >> >> >> >>
>> >> >> >> >> I have just started to use VTK to fulfill my visualization
>> >> >> >> >> needs.
>> >> >> >> >> I
>> >> >> >> >> am
>> >> >> >> >> trying out few fundamental steps which would be crucial for my
>> >> >> >> >> future
>> >> >> >> >> development.
>> >> >> >> >>
>> >> >> >> >> I exported an  Finite Element Model (FEM) from COMSOL and
>> >> >> >> >> wrote
>> >> >> >> >> it
>> >> >> >> >> as
>> >> >> >> >> vtk
>> >> >> >> >> unstructured grid in matlab (points, connections and data). I
>> >> >> >> >> am
>> >> >> >> >> just
>> >> >> >> >> trying
>> >> >> >> >> to read my vtk file and trying to visualize the isosurfaces at
>> >> >> >> >> some
>> >> >> >> >> value.
>> >> >> >> >>
>> >> >> >> >> The problem is the isosurfaces are very rough even when I
>> >> >> >> >> increased
>> >> >> >> >> the
>> >> >> >> >> mesh
>> >> >> >> >> density in my COMSOL model. I tried to perform the same task
>> >> >> >> >> in
>> >> >> >> >> paraview and
>> >> >> >> >> even there i saw the same problem.
>> >> >> >> >>
>> >> >> >> >> Do you think that increasing the mesh density should solve it?
>> >> >> >> >> I
>> >> >> >> >> cannot
>> >> >> >> >> increase the mesh density because of computational issues. Any
>> >> >> >> >> ideas
>> >> >> >> >> on
>> >> >> >> >> this
>> >> >> >> >> problem will be appreciated.
>> >> >> >> >>
>> >> >> >> >> Thank you,
>> >> >> >> >>
>> >> >> >> >> Sanket Jain
>> >> >> >> >>
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>> >> >> >> >>
>> >> >> >> >
>> >> >> >
>> >> >> >
>> >> >> >
>> >> >> > --
>> >> >> > Sanket Jain
>> >> >> >
>> >> >
>> >> >
>> >> >
>> >> > --
>> >> > Sanket Jain
>> >> >
>> >
>> >
>> >
>> > --
>> > Sanket Jain
>> >
>
>
>
> --
> Sanket Jain
>