[vtkusers] vtkCamera and OffAxisProjection stereo rendering

[David Cole]

Hi,

The documentation on the OffAxisProjection related methods is pretty sparse.

I'm working on an app that uses off axis projection, and the user is
able to toggle it on and off dynamically while running the app. I have
the following problems while trying to get this working...

- The lighting seems wrong when using the off axis projection. It
appears properly when I align the view to look down on the world Z
axis, as if the light is always coming from there. Why doesn't the
camera light adjust properly so that it points from the camera to the
scene when using off axis projection? Is it just a bug?

- The view changes drastically when I toggle back and forth between
using off axis projection and the normal perspective projection. Why
isn't the view just the same (except taking the eye into consideration
instead of the on-axis camera...)?? Seems like I should see the same
stuff from the same angle when I turn on OffAxisProjection, but it
**appears** to change the camera's position, focal point and viewup
vectors without those values **actually** changing.

I guess these two are actually the same question: why does the scene
change when I specify the Screen parameters and EyePosition in world
coordinates?

It seems like I must have something set incorrectly.

Do the ScreenBottomLeft and related Screen* parameters refer to the
physical screen being used to display the app's window? Or to the
window itself within the app?

And, since this modifies the projection transform, are the vtkRenderer
methods ViewToWorld and WorldToView still expected to work properly
when off axis projection is being used?


Thanks for any advice, hints, help, and/or doc updates,
David C.