anaglyphic stereo, backprojection & screendistance

[malte]

Hello all,
I have a question regarding anaglyphic stereo (red/green): We do have backrojection system and want to use anaglyphic stereo. To increase viewers' FOV, they will be seated rather close to the projection screen. The simulated FOV matches viewers' physical FOV (~90° hor x 75° vert).
If I now play around with the screendistance settings (vizcore.cfg: e.g. viz.screenDistance = 1), the distance for which the anaglyphic stereo is calculated changes (the manipulations do in principle work). However, it changes in ways I do not understand. Maybe I am missing something. Originally, I thought that I just have to measure the viewers' distance from the backprojection screen and use this as the screendistance (does not work). Is it possible that the large physical FOV is causing the problems?
Thanks for feedback!
-Jan