[vtkusers] Hardware offscreen rendering (and its possible use for the Java wrappers)

[Sebastien Jourdain]

Hi Luke,

I can agree and if you do the thing smartly you can use another
dedicated thread for VTK than the EDT. But unfortunately, it doesn't
seem that easy. I think that Karthik did try something like that and
the performance were very poor.
Moreover, we might run into multi-platform issue on the C++ layer in
the way the OpenGL context get truly created.

Karthik can you elaborate your experience in that domain if any ?

Thanks,

Seb

On Wed, Oct 19, 2011 at 10:53 AM, Luke Dodd <luke.dodd at gmail.com> wrote:
> Hi,
>
> It seems that hardware (NOT mesa) based offscreen rendering is not
> supported in VTK. But the existence
> vtkOpenGLRenderWindow::CreateHardwareOffScreenWindow method, and my
> personal experience with using OpenGL frame buffers make me think it
> really shouldn't be so hard to achieve. Of course the aforementioned
> methods are protected so I'm not sure how or if I'm supposed to go
> about using them (inheriting from vtkOpenGLRenderWindow doesn't seem
> like something I'm supposed to do). Also I think if it were actually
> easy to achieve then it would have already been done.
>
> The reason I'm thinking about this is that decent hardware offscreen
> rendering I think it could be easy to implement a vtk panel in java
> that uses offscreen rendering, and standard java 2D graphics API to
> put that offscreen image onscreen. It sounds convoluted but it would
> skip all the hassle with lightweight vs heavyweight components,
> eliminate the need for the extra JNI code the vtkPanel currently uses,
> and the vtkRenderWindow leaks that currently occur under Linux. I just
> did a quick test, and it seems to me, that reading glReadPixels does
> work fast enough for this to be possible unless one needs really high
> frame rates.
>
> So I'm asking: is this possible with standard VTK? Would this be
> possible with a few tweaks? Am I missing some great complication when
> I think it shouldn't be hard to implement? And finally anyone else
> interested in this?
>
> Best,
> Luke Dodd
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