Re: Porblems with off screen rendering of contour lines....

Hi Surekha,

Can you call getImage() and print using your original
on-screen DisplayImplJ3D? If so, that would be the
easiest way to work around this problem.

We've known about problems with getImage() from offscreen
DisplayImplJ3Ds for quite a while, but despite some
intensive effort haven't been able to fix them. The fact
that you see problems with contour lines but not with
surfaces is a sign that this is a problem in Java3D or
even OpenGL, since the VisAD code for getImage() doesn't
know anything about lines versus surfaces.

There is a VisAD standard test (that we run before
every release) for getImage() from an offscreen
DisplayImplJ3D, in the main() method of
visad/java3d/VisADCanvasJ3D.java. This repeatedly
calls getImage() from an offscreen DisplayImplJ3D and
then displays the returned BufferedImage in a JPanel
via a call to drawImage(). The test in the main()
method of VisADCanvasJ3D renders a simple texture
map, but I was able to change it to render contour
lines by appending:

  display.addMap(new ScalarMap(vis_radiance, Display.IsoContour));

to the string of addMap() calls in the main() method.

When I did this, the JPanel didn't display the contour
lines until the second call to drawImage(). This suggests
a possible work-around for your problem: replicate the
logic of main() calling getImage() twice (or more if
necessary) with calls to Thread.sleep(1000) between
successive calls to getImage(). Kind of a hack, but it
might work.

Good luck,
Bill

On Thu, 1 Dec 2005, Surekha Chandran wrote:

> Hi all,
>
> I am trying to print out an DisplayImplJ3D image by
> doing the following steps:
> 1. I create an new off screen DisplayImplJ3D
> "offscreenDisplay"
> 2. I clone the ScalarMaps from the original visible
> display and add it to the "offscreenDisplay"
> 3. I add the DataReferenceImpl from the original
> visible display to the offscreenDisplay.
>
> Everything seems to work. Except when I do the next
> step of actually printing out the image. The .jpg file
> is empty!
>
> This only happens with contour lines. I am able to
> print surfaces but not contours.
>
> Can anyone help? I am at a complete loss.
>
> There are times that I seem to be hanging on the
> statement :
> java.awt.image.BufferedImage buffImage
> offscreenDisplay.getImage(true);
> I don't know why that happens.
>
> I will settle for being able to see the contours in my
> output files from the offscreenDisplay.
>
> Thanks
> Surekha
>
>
>
>
>
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