[vtk-developers] strange behaviour in vtkVolumeTextureMapper2D

[Sebastien BARRE]

At 08:38 13/07/00 -0400, Lisa Sobierajski Avila a écrit:

Thanks for your help Lisa.

>We have seen some strange behavior here on a Sun which I suspect also 
>originates from my recent changes. (The volume doesn't disappear - extra 
>"garbage" is rendered all around the volume - what should be far outside 
>the vertices of the quads).

Strange indeed.

>  I'll look into it. What I don't understand is how altering the vertex 
> coordinates just a bit can seriously affect the rendering. I made the 
> change in response to another user who noticed that it should be size-1 
> instead of size

I've just found that email in my archive.

>(because 2 samples only cover a distance of 1 sample spacing between 
>them). One other change I believe I made at the same time was to go from 
>rendering polygons to rendering quads - maybe that has something to do with it.

Nope, I've tested that already, replacing the new code with the old 
(rectangle). No differences, bug remains.

>Everything works find on Oxygen VX1, TNT2, and GeForce boards.

It works also fine on my Oxygen GMX 2000 at home... But it's quite 
disturbing here on my SGI 320 :)

BTW : also you might resample the volume and use a LOD to mix both a 
low-res and hi-res volumeTextureMapper2D, I was wondering if it would be 
possible to add a parameter for that class that could specify that one just 
want every 2- or every nth- quad (rectangle) to be used. I guess this would 
speed up thing, but I do not know about the quality, is it better than 
resampling to n/2 or n/3 ? I've played with iinc, jinc, and kinc, then 
changed a couple of tests from == to <=, it looks like it worked, but I'm 
really not sure about what I'm doing, and as it's a very useful class, I do 
not want to break it too soon :)

BTW2 : I've sent a mail to the VolumePro guys. Jesus it's expensive !  $ 
5500 ! (25% discount for university, but wow). Is it really worth it ? We 
are expecting a GeForce here, and I'm quite impatient to see how it deals 
with the volumeTextureMapper2D. I'm gonna test it with Voodoo 3 this week also.

--
Sebastien BARRE
IRCOM-SIC, UMR-CNRS 6615 - Université de Poitiers
Bât. SP2MI, Bvd 3 - Téléport 2, BP 179 F-86960 Futuroscope Cedex
Tel. : +33 (0)5 49 49 65 92, Fax : +33 (0)5 49 49 65 70
http://www-sic.univ-poitiers.fr/barre/ ou  http://www.hds.utc.fr/~barre/ 
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