Hi Manfred, hi Allan,
On Wed, 2005-01-05 at 04:44, Manfred Weiler wrote:
> > Now I need to read back the plane where the volume is cut as a 2d
> > texture. What I gathered so far is that the ClipPlaneChunk is not the
> > way to go, but I haven't been able to find any documentation about this
> > in OpenSG/Source/System/NodeCores/Drawables/VolRen.
>
> Unfortunately the volume node does not support such slice extraction
> from the volume data so far. Of course you could just reduce the slice
> number (or sampling distance) so that only one slice plane is drawn, but
> this would not be at the position you like to have. So depending on your
> actual task and your will to perform modifications to OpenSG itself
> I see different solutions:
>
> 1. You could use two clip planes with a distance sufficient for exactly
> one slice plane. By cutting away also the back of the volume you
> would thereby create a single cut slice of the volume.
This sounds like the simplest solution. I'm just not sure if that gives
Allan enough control, as it doesn't really extract only a single slice.
> 2. You could use a 3D-Texture of your own and render a single slice inside
> this volume with the texture mapped on that slice. This would have the
> advantage that your slice could have any orientation with respect to
> the volume or the view direction. Unfortunately this would require to
> compute intersection of the cutting plane with the bounding box of
> the volume yourself.
Ok, you lost me here. ;) Can you rephrase that?
> 3. The cleanest and imho not so difficult solution would be to extend the
> volume node so that you can extract a single slice only. (Which is
> probably done best in a derived or maybe decorated class) You could
> use the slicing code of the volume node and also most of the other
> functionality would work transparently. To get an impression what
> has to be done and where to start I suggest to look at
> Brick::render3DSlices.
It would be a bit of work, but nothing excessive, I agree. You'd have to
extend the Brick a little to get easier access to the single slice
drawing, and either extend or derive the DVRVolume.
I think the easiest solution would be 1), if it's what you need. I have
no clue about 2) and 3) would be the cleanest, but probably more work.
Hope it helps
Dirk
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