[vtkusers] stereo rendering with volumepro1000, not working properly?

[Dr. Daniel James White PhD]

Hey Kristen,

I hope you can pass this on to your technical people.
VTK stereo people may want to look also.

I have questions about using my new volumepro1000 hardware volume 
rendering / ray casting board to do stereo volume rendering using 
VTK/openGL quad buffered (page flipping) stereo with crystal eyes 
glasses, on my red hat  linux machine, with xig.com accelerated X 
server (for quad buffered stereo using the ATI Radeon 8500 graphics 
card and crystal eyes lcd shutter glasses system)

My stereoscopic viewing system works with several 3D/stereo enabled 
programs, for molecular modeling and other stuff, such as bodil, pymol, 
VMD......These all use OpenGL stereo rendering with polygons.

Also with the VTK program I am using, called MayaVi, stereo has been 
enabled, and works great for iso surface rendering  in both parallel 
and perspective projection modes.

I have noticed that there are problems with the VTK software raycasting 
code (vtkCompasiteRayCastMapper I think it is called) that seem to make 
the stereo rendering left right swapped, or at least some how weird for 
volume rendering. I think is supposed to be getting fixed in VTK...is 
it?..... anyway

So I tried the stereo viewing mode using the VTK volumepro1000mapper, 
which we are testing (with good results in mono)  in MayaVi. There are 
problems...

1) The left and right eye images are made, but they have no "depth". 
The volumepro generated image looks "flat" and in the plane of the 
monitor, whereas an iso surface rendered image jumps out of the screen 
at you nicely, as it should.

2) (maybe the same problem) In parallel viewing with 
volumepro1000mapper and isosurface rendering in the same window, opaque 
iso surface rendered stuff close to the camera looks like it is in 
front of the volumepro100 rendered image, and  opaque iso surface 
rendered stuff far  away to the camera looks like it is behind the 
volumepro100 rendered image. As the data set is rotated the iso surface 
rendered stuff appears from behind and then vanishes behind the volume 
rendered image of the same feature in the data.
  In perspective viewing the same is true.

3) In parallel projection, If I turn on the inter mix intersecting 
geometry flag on, then the volumepro1000 left and right eye images jump 
apart on the screen, and with the shutter glasses on, the image looks 
like it is just in front of the screen, but still "flat". In 
perspective projection, the left and right images with mix intersecting 
geometry on, the left and right images move further apart the more 
"side on" I view the data set.

So I wonder..... the VP1000 board and vli3 library  can do a 
perspective or parallel  projection just fine for a single camera 
position or eye, but when it uses 2, something is going wrong with the 
camera positions, such that they are not left and right eye, but 
something else. I know parallel projection should never really work for 
left/right eye stereo, but the perspective projection should work 
right?

Is this a problem with VTK, or vli3 (the VP1000 driver), or the 
VP1000board, or what?
I see no reason why OpenGL stereo perspective projection volumepro1000 
rendering should not work in theory. VTK/vli3 just has to talk to 
openGL properly to make the left and right images come from the correct 
camera positions..... right?

Am I doing something wrong or missing a point?

Why does the intermixintersectinggeometry flag have this effect?

Any ideas?
cheers

Dan


Dr. Daniel James White BSc. (Hons.) PhD
Cell Biology
Department of biological and environmental science
PO Box  35
University of Jyväskylä
Jyväskylä FIN 40014
Finland
+358 (0)14 260 4183 (work)
+358 (0)414740463 (mob)

http://www.chalkie.org.uk
dan at chalkie.org.uk
white at cc.jyu.fi