From: Dave Akers (dla@engr.sgi.com)
Date: 08/01/2000 12:51:29
Hi,
For what you're trying to do there are a couple of possible approaches..
1) You could use T3F_V3F format for your geometry specification,
explicitly encoding texture coordinates for each vertex. (You could use an
indexed hexa set to store the geometry, then use its tesselate() method to
create tetras..)
2) You could resample your texture into a uniform cube grid structure,
padding the outside regions with zeroes.
There are many trade-offs between the above techniques.. I'd be happy to
go through it in more detail if you would like.
As for truncation of texture data, try using a different partial brick
type. See /usr/share/Volumizer/src/apps/OpenGL/voglInitAppearance.cxx. In
your call to voAppearanceActions::getBestParameters it sounds like you are
using voPartialBrickTypeScope::TRUNCATE. Try using either AUGMENT or
AUGMENT_TIGHT. AUGMENT will create an extra same-sized brick and pad it
with zeroes, while AUGMENT_TIGHT will create an extra row of tight-fitting
bricks along the edges. If you're using Volumizer 1.2 AUGMENT_TIGHT will
work correctly - previously a bug from 1.1 resulted in incorrect sorting
of the bricks in AUGMENT_TIGHT mode.
Hope that helps,
-Dave
On Sat, 29 Jul 2000, K. R. Subramanian wrote:
>
> I am new to the volumizer mailing list and have just been going through
> the volumizer
> user guide and examples..
>
> I am trying to volume render vascular data - its a structured grid
> data, i.e. its a sequence of
> 2D images, but they are not axis aligned (like a bent tube). It seems
> like I have to generate
> the volume geometry to reflect this. I have the object coordinates at
> each lattice point of the
> volume. So should I take short segments of the vessel geometry and
> approximate them by
> cubical segments and convert each of these into tetrahedra? The texture
> data is topologically
> equivalent to a 3D cube. Would this work?
>
> Also, volumizer (in its examples) takes volumes of size such as
> 256x256x109 and constructs
> just 1 brick of size 256x256x64. To make it use the full volume, is it
> sufficient to pad the additional
> slices so as to make it go up to 256x256x128. In this case, would it
> render the full volume?
>
> Thanks.
>
> -- krs
>
> --
> Dr. K.R.Subramanian Phone: (301) 435-3264
> National Institutes of Health FAX: (301) 402-4080
> National Library of Medicine Email: krs@cs.uncc.edu
> Bldg 38A, Rm. B1N30D WWW: www.cs.uncc.edu/~krs
> 8600 Rockville Pike, Bethesda, MD 20894
>
>
>
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