[vtkusers] Animation of multiple input files in VTK

Thu Jul 7 07:14:45 EDT 2011

I (think that I) am allready precomputing the marching cubes. See my code
snippet below, I think this would mean that the marching cubes are
pre-calculated and can be cached?

for(int i = 0; i < numberOfFrames; ++i)
{
reader[i] = vtkSmartPointer<vtkStructuredPointsReader>::New();
std::stringstream name;
 name << "C:/Temp/vtk/FTLE" << (i+1) << ".vtk";
cout << "Loading: " << name.str();
 reader[i]->SetFileName(name.str().c_str());
reader[i]->Update();

 cout << ", and calculating ISO surface\n";
// Create surfaces between range specified
 contours[i] = vtkSmartPointer<vtkMarchingCubes>::New();
contours[i]->GenerateValues(10, minValue, maxValue);
 contours[i]->ComputeNormalsOn(); // fancy and expensive
contours[i]->ComputeScalarsOn();
 contours[i]->SetInputConnection(reader[i]->GetOutputPort());
contours[i]->Update();
}

On Thu, Jul 7, 2011 at 1:04 PM, Dominik Szczerba <dominik at itis.ethz.ch>wrote:

> > When I load this sequence in Paraview, it is able to run very smoothly
> > (after the first run, which takes some time) while still allowing the
> user
> > to interact. Does anyone know how Paraview does this?
>
> Probably by caching. Why not precompute marching cubes prior to rendering?
>
> Dominik
>
> >
> > Tijmen
> >
> > On Wed, Jul 6, 2011 at 5:46 PM, Shashwath T.R. <trshash at gmail.com>
> wrote:
> >>
> >> Why not have multiple vtkMarchingCubes instances - one for each input,
> and
> >> then multiple mapper/actor sets? You could select which one you want to
> work
> >> on, and make the rest invisible...
> >> Shash
> >>
> >> On Wed, Jul 6, 2011 at 4:37 PM, Tijmen Klein <T.R.Klein at student.rug.nl>
> >> wrote:
> >>>
> >>> This is what I do. I set up the whole scene, load in all the different
> >>> readers, and connect the first reader to the vtkMarchingCubes. Then I
> use a
> >>> timer that calls an update function every second. This update function
> sets
> >>> the inputconnection of the vtkMarchingCubes to the current reader
> >>> (contours->setInputConnection(reader[current]->getOutputPort()). This
> is
> >>> working, but results in small (but very noticable) hickups in the
> >>> interaction. I think this is because the isosurfaces have to be
> >>> re-calculated every time. That's why I think that I will need an array
> of
> >>> vtkMarchingCubes too.
> >>>
> >>> Tijmen
> >>>
> >>> On Wed, Jul 6, 2011 at 11:02 AM, Dominik Szczerba <
> dominik at itis.ethz.ch>
> >>> wrote:
> >>>>
> >>>> You should update your reader only from a callback function once you
> >>>> have your scene/camera/etc set up...
> >>>>
> >>>> Dominik
> >>>>
> >>>> On Wed, Jul 6, 2011 at 10:51 AM, Tijmen Klein <
> T.R.Klein at student.rug.nl>
> >>>> wrote:
> >>>> > Thank you for the reply. First of all, I'm not trying to export a
> >>>> > animation;
> >>>> > it should be realtime and allowing the user to navigate the scene.
> >>>> >
> >>>> > I'm currently applying the fist technique (update the reader in a
> >>>> > loop).
> >>>> > Technically this works fine, but it is really slow and also blocks
> the
> >>>> > mean
> >>>> > thread of the program (the program simply freezes when switching
> >>>> > between 2
> >>>> > frames). A possible solution that I came up with is the following:
> >>>> > create N
> >>>> > pipelines (up to the mapper), where N is the number of frames. This
> >>>> > mean I
> >>>> > can load the data first, create the isosurfaces and then based on
> the
> >>>> > current time let the actor point to the corresponding mapper. This
> >>>> > would
> >>>> > mean that all the calculations are already completed.
> >>>> >
> >>>> > Is this a viable solution? It feels a bit hack-ish to do it like
> this.
> >>>> >
> >>>> > Tijmen
> >>>> >
> >>>> > On Tue, Jul 5, 2011 at 4:00 PM, Dominik Szczerba
> >>>> > <dominik at itis.ethz.ch>
> >>>> > wrote:
> >>>> >>
> >>>> >> There are a few possibilities. The simplest would be to update the
> >>>> >> reader in a loop and dumping screen renderings. More sophisticated
> >>>> >> would be to import them first into a temporal dataset and then
> >>>> >> request
> >>>> >> a specific time value.
> >>>> >>
> >>>> >> Dominik
> >>>> >>
> >>>> >> On Tue, Jul 5, 2011 at 2:57 PM, Tijmen Klein
> >>>> >> <T.R.Klein at student.rug.nl>
> >>>> >> wrote:
> >>>> >> > I'm trying to animate multiple input files. These files are in
> the
> >>>> >> > legacy
> >>>> >> > VTK format (.vtk), and named filename[x].vtk, where [x] is an
> >>>> >> > integer. A
> >>>> >> > contourfilter is used to generate isosurfaces, and these
> >>>> >> > isosurfaces
> >>>> >> > should
> >>>> >> > be animated.
> >>>> >> >
> >>>> >> > This is behaviour that is quite easy to achieve in Paraview (open
> >>>> >> > the
> >>>> >> > files,
> >>>> >> > apply contour filter, choose a frame or click play). How can
> >>>> >> > something
> >>>> >> > similar be achieved in VTK? It should be possible to create a
> >>>> >> > time-dependent
> >>>> >> > animation, but also manually set the current frame. I thought of
> >>>> >> > creating
> >>>> >> > multiple InputReaders, and have the 'current' reader's outputport
> >>>> >> > connected
> >>>> >> > to the input port of the contour filter. But I think this would
> not
> >>>> >> > be
> >>>> >> > very
> >>>> >> > efficient, since it's not possible to cache the results in this
> >>>> >> > way.
> >>>> >> > This
> >>>> >> > would mean that all the calculations happen again when the
> >>>> >> > animations
> >>>> >> > restarts from frame 1. What would be a better solution?
> >>>> >> >
> >>>> >> > Cheers,
> >>>> >> > Tijmen
> >>>> >> >
> >>>> >> > _______________________________________________
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> >>>> >> >
> >>>> >
> >>>> >
> >>>
> >>>
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