[vtkusers] Make Smooth Isosurfaces

[Bill Lorensen]

The file and data seem OK. I looked at it in paraview and I see the
same sort of "rough" isosurfaces that you see.  Can you generate an
isosurface in COMSOL for comparison?

Bill

On Fri, Oct 30, 2009 at 12:36 PM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> 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
>>
>