FW: [vtkusers] Embedded geometry with VolumePro500 & VTK

[Ron Inbar]

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-----Original Message-----
From: Ron Inbar 
Sent: Tuesday, March 04, 2003 10:23 PM
To: 'Martin Gardner'
Subject: RE: [vtkusers] Embedded geometry with VolumePro500 & VTK

Hi Martin,

As far as I know, the VP500 can't do embedded geometry, so it surprises me
you were able to see anything.  Did you get a three-dimensional,
geometrically-correct result?  I guess not.

As you may already know, the VolumePro (both the 500 and the 1000) projects
the volume onto an OpenGL texture image, which it then maps onto a hexagon.
To correctly embed polygonal geometry in the resulting image, the VolumePro
hardware pipeline has to take its color and depth information into account
during execution, and produce a texture map that includes the correct
colors.  This is only done by the VP1000.  If you simply try to render the
VolumePro hexagon along with the other geometry, the result will be
incorrect, because as far as OpenGL is concerned, the VolumePro image is
just a flat hexagon.

It's another matter if the geometry doesn't intersect the volume, for
example if you enclose the volume by a wire-frame box, such as the one
produced by vtkOutlineFilter.  In this case, the geometrically-incorrect
scene may look indistinguishable from the correct scene when projected onto
the two-dimensional screen.

(I have the VP500 myself so I'm not 100% sure I understand the VP1000
geometry-embedding technique, but I'm pretty sure it can't be done after the
volume is already projected onto the hexagon.)

Ron

-----Original Message-----
From: Martin Gardner [mailto:mglistmail at totalise.co.uk] 
Sent: Tuesday, March 04, 2003 8:21 PM
To: vtkusers at public.kitware.com
Subject: [vtkusers] Embedded geometry with VolumePro500 & VTK

Hi,

Does anyone have any tricks for getting embedded geometry to work nicely 
with the VolumePro 500?  I've asked TeraRecon and they say it isn't 
supported on the VP500 and I'll have to get the VP1000 :(.

The sample app that comes with the VP500 manages to do some embedded 
geometry at the price of frame rate.  So while the board doesn't 
specifically support it, it may be possible to hack something together 
in OpenGL/VTK. But I'm new to vtk so I'm hoping someone else will be 
able to point me in the right direction.


Thanks in advance

Martin

--
Martin Gardner
mglistmail at totalise.co.uk

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