[vtkusers] Offscreen Rendering

[Michael Hoffer]

Hi Sebastien,

thanks for your answer. I have checked vtkPanel. But it seems to be a
heavyweight AWT component. Java 7 is currently no option for me and I need
real transparency etc. There is no easy way to access the pixel data from
Java and it seems like vtkPanel only works if it is atached to a JFrame. Is
that correct?

I chose to create an alternative implementation. I uploaded it to GitHub:
http://miho.github.com/JVTK/

The project contains a pure lightweight Swing panel that uses a vtkPanel
internally. The panel converts the native pixel data to an AWT image that
is used to paint the Swing panel. I implemented basic fullscreen support.
In fullscreen mode the internal vtkPanel is used. This allows full render
performance.

The project contains a sample application that demonstrates its features.

It would be nice if you could check my implementation. Maybe there is a
better way to convert pixeldata...

Regards,
Michael

2012/5/28 Sebastien Jourdain <sebastien.jourdain at kitware.com>

> I think you have a better solution on your end since you are using Java.
> The idea is to use a vtkPanel or vtkCanvas directly without inserting
> it in a graphical component. Somehow, it will be offscreen and you
> will keep the GPU acceleration.
>
> Let me know how it goes.
>
> Seb
>
> On Sun, May 27, 2012 at 3:48 PM, Michael Hoffer <info at michaelhoffer.de>
> wrote:
> > Hello,
> >
> > i am totally new to VTK. First of all, I was really surprised how easy
> it is
> > to setup VTK with Java. I compiled it on Linux and OS X. Well done!
> >
> > Now my question: as I am interested in offscreen rendering I tried the
> > example below. It worked but unfortunately an empty window was shown. I
> > didn't expect a window. Do I really have to completely switch hardware
> > acceleration off by using VTK_OPENGL_HAS_OSMESA? Couldn't I just hide the
> > window? If it is possible, how do I do that?
> >
> > My intention is to write a pure Swing component that uses offscreen
> > rendering. I know that this will slow down everything. But my views will
> be
> > relatively small in size (e.g. 300x200 pixel). Thus, the performance
> should
> > be ok as long as getting the native memory isn't too time consuming. I
> have
> > seen that there are some approaches that also tried that. But all code
> > samples I have seen looped over the vtk array to copy it to an
> image. This
> > is definitely too slow. But using WritableRaster, DataBuffer etc. should
> > help.
> >
> > Thanks for your help!
> >
> > Regards,
> > Michael
> >
> > //
> > // code originally
> > from
> http://www.vtk.org/Wiki/VTK/Examples/Cxx/Utilities/OffScreenRendering
> > //
> > import vtk.*;
> >
> > /**
> >  *
> >  * @author Michael Hoffer info at michaelhoffer.de
> >  */
> > public class VTKOffscreenSample {
> >
> >     public static void main(String[] args) {
> >
> >         loadLibraries();
> >
> >         // Setup offscreen rendering
> >         vtkGraphicsFactory graphics_factory = new vtkGraphicsFactory();
> >         graphics_factory.SetOffScreenOnlyMode(1);
> >         graphics_factory.SetUseMesaClasses(1);
> >
> >         vtkImagingFactory imaging_factory = new vtkImagingFactory();
> >         imaging_factory.SetUseMesaClasses(1);
> >
> >         // Create a sphere
> >         vtkSphereSource sphereSource = new vtkSphereSource();
> >
> >         // Create a mapper and actor
> >         vtkPolyDataMapper mapper = new vtkPolyDataMapper();
> >         mapper.SetInputConnection(sphereSource.GetOutputPort());
> >
> >         vtkActor actor = new vtkActor();
> >         actor.SetMapper(mapper);
> >
> >         // A renderer and render window
> >         vtkRenderer renderer = new vtkRenderer();
> >         vtkRenderWindow renderWindow = new vtkRenderWindow();
> >         renderWindow.SetOffScreenRendering(1);
> >         renderWindow.AddRenderer(renderer);
> >
> >         // Add the actors to the scene
> >         renderer.AddActor(actor);
> >         renderer.SetBackground(1, 1, 1); // Background color white
> >
> >         renderWindow.Render();
> >
> >         vtkWindowToImageFilter windowToImageFilter = new
> > vtkWindowToImageFilter();
> >         windowToImageFilter.SetInput(renderWindow);
> >         windowToImageFilter.Update();
> >
> >         vtkPNGWriter writer = new vtkPNGWriter();
> >         writer.SetFileName("screenshot.png");
> >         writer.SetInputConnection(windowToImageFilter.GetOutputPort());
> >         writer.Write();
> >     }
> >
> >     private static void loadLibraries() {
> >
> >         if (!vtkNativeLibrary.LoadAllNativeLibraries()) {
> >             for (vtkNativeLibrary lib : vtkNativeLibrary.values()) {
> >                 if (!lib.IsLoaded()) {
> >                     System.out.println(lib.GetLibraryName() + " not
> > loaded");
> >                 }
> >             }
> >
> >             System.out.println("Make sure the search path is correct: ");
> >             System.out.println(System.getProperty("java.library.path"));
> >         }
> >
> >         vtkNativeLibrary.DisableOutputWindow(null);
> >     }
> > }
> >
> >
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>



-- 
Dipl.-Math. Michael Hoffer

Goethe-Zentrum für Wissenschaftliches Rechnen (G-CSC)
Goethe-Universität
Kettenhofweg 139
60325 Frankfurt am Main
Tel.: +49 69 798 25254
michael.hoffer at gcsc.uni-frankfurt.de
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