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

[Lisa Avila]

Hello Dan,

If your ray cast mapper is not correctly working in stereo, then the 
VolumePro mapper won't either - you are still using a version of VTK with 
the "bug" in it. I know we fixed it on a branch - I'll have to check 
tomorrow whether it is fixed on the main tree or not. The problem was 
(maybe is) that the left/right flag was switched right after setting up the 
camera for that eye - which means that by the time these volume mappers 
asked for the current matrix the wrong one was returned.

So - if you had the fix the ray cast mapper would work, but I am still not 
sure about the VolumePro mapper. I believe that we set up the matrix is VLI 
by using just the position / focal point from the camera (which I do not 
believe are altered at all in stereo mode). The disparity you are seeing is 
because the matrix for OpenGL changes between eyes, and the texture mapped 
polygons (with the results from the board)  are rendered in two different 
places because of this. The images themselves will be identical.

I have to look at the code in vtkCamera to see what is done in parallel for 
stereo rendering - I am not sure this is intended to work at all (it does 
not really make sense, right?) And the VolumePro mapper only works in 
parallel......

Lisa


At 11:47 AM 3/9/2004, Dr. Daniel James White PhD wrote:
>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
>_______________________________________________
>This is the private VTK discussion list. Please keep messages on-topic. 
>Check the FAQ at: <http://public.kitware.com/cgi-bin/vtkfaq>
>Follow this link to subscribe/unsubscribe:
>http://www.vtk.org/mailman/listinfo/vtkusers