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

[Dr. Daniel James White PhD]

Hi Lisa,

On 10 Mar 2004, at 17:04, Lisa Avila wrote:
>>
>> My VTK is a recent CVS build, and it looks like the bug was not fixed 
>> in that. It was built after Xmas.
>> How can I check my present code for the bug fix?
>
> That probably means the fix never made it from the branch to the main 
> tree.
>

OK..... so when will it be there in CVS for met to download, or where 
do it get it otherwise?

>> Surely the volumepro1000 board should be able to make 2 images , one 
>> from each eye, and send them to VTK in both perceptive and parallel 
>> modes, then it should just work right?
>
> In VTK stereo is performed with an off-axis (sheared) projection 
> matrix applied to the current camera matrix.

so its not really 2 different camera positions? Its some other cleverer 
way of doing it I didn't realise....

> Although this does not entirely make sense in parallel (you are trying 
> to add depth cues to something where depth is ignored in the 
> projection matrix....) you are probably getting some cues from the 
> fact that each eye sees something slightly different. I do not believe 
> there is any way to set up a corresponding matrix (to what VTK does) 
> with VLI - in the version that existed when the mapper was written VLI 
> only supported orthogonal viewing matrices.

the volumepro1000 now has a perceptive mode which is supported by vli3 
on linux and works in vtk, but not for zooming, only rotation, it 
seems, at the moment.

>
> Also - you should not be using a perspective matrix with a VolumePro 
> mapper - it should be spewing out a bunch of warnings, although I 
> believe it will go ahead and render the image anyway pretending it has 
> a parallel viewing matrix. This will not be correct - you are 
> rendering one object in the scene with a different viewing matrix than 
> all the others.

I guess now it does do perspective, but actually VTK does send error 
messages I if I remember, complaining about the camera needing to be 
parallel. but it still works in perspective, at least for rotation. We 
changed  the default camera to parallel in our volumepro1000 module for 
Mayavi. But you can change it to perspective and the view changes 
appropriately.
>
>
>> Yes, I guess parallel stereo doesn't make physical or theoretical 
>> sense, BUT, at least using my setup and my eyes, the parallel image 
>> using isosurfaces "looks" good, and there is a good impression of 
>> depth...... so I suppose it might "work" for ray casting methods 
>> also. The thing is, at present only the parallel mode is able to zoom 
>> in and out using volumepro1000. The perspective mode using 
>> volumepro1000 does work, but not zooming, only spinning around.
>> So it would be nice to use pseudo-nonsense-but-still-looks-ok stereo 
>> in parallel mode with the volumepro1000 mapper....
>> I hope the VTK bug fix corrects this....?
>
> Nope - fixing the "bug" will only fix the issue for ray casting (which 
> can create off-axis projections), not for the VolumePro mapper.

So you are saying that the volume pro1000 mapper is now outdated and it 
needs to be updated for new vli3 and volumepro1000 capabilities, like 
perspective and others.

>
>
>> If I can show people stereo3D real time zooming and spinning of their 
>> confocal microscope data, volume rendered using the volumepro1000 
>> board, they and my boss will be very happy!
>
> I think you'll have to either do some development for this, or look 
> outside of VTK for a solution (using VLI directly). You will also need 
> to obtain the perspective "option" from TeraRecon (I'm not sure what 
> their policy/pricing is on this). With this option you may be able to 
> ask the board to generate an off-axis projection for stereo.

I have the perspective option, it works.

Surely its best to fix vtkvolumepromapper1000 so that all users can 
more easily see the benefits of the new vli3 and vp1000 hardware 
functions? Especially since VTK is supposed to be fully compatible with 
volumepro.....right... sure I read that somewhere.... or was it the 
other way around?

>
> Have you tried VolView 2.0?  Stereo is a "hidden" feature of VolView 
> (you have to know to start it with the -3 option from a command line!) 
> but does work for both ray casting and 3D texture mapping. (VolView 
> 2.0 does not support the VolumePro). If you have a "supported" video 
> card (like the NVidia GeForce 3, 4, or FX, or the ATI Radeon 9700+) 
> then you will get interactive rendering rates with decent "interactive 
> image quality" in stereo (with perspective too).
>

I only run windows under emulation in extreme "last resort" situations. 
I use OSX and linux because I am an academic scientist and it makes 
more sense not to rely on windows to give me viruses and blue screens. 
We are open source developers trying to lever the best performance out 
of inexpensive consumer hardware, which includes VP1000 in this case. 
The board is not that expensive. Macs are cheap, powerful and very 
reliable. Linux is very cheap / free and can be extremely fast. Windows 
isn't.

I'm sure a volview2.0 version for OSX would be snapped up by academics!

Can you really get "interactive full resolution frame rates" with 3D 
texture mapping or ray casting in volpro2.0 for an 8 bit scalar data 
set of 512x512x100-512? We are microscopists, so detail and resolution 
are everything.

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