At the moment (by August 2016) stacked projection setups cannot be calibrated using the WINGS VIOSO dialogue. Instead, please use the VIOSO Calibrator as a standalone program and follow the steps below to perform a camera based calibration for stacked projection:
1. Set up the graphics outputs of the WINGS media servers as a separate virtual display group for every stack level.
You are using a 4-head WINGS machine and want to do a 2-projector panorama as a double stack of FullHD projectors. Combine each 2 outputs as a virtual stretched display (nVidia mosaic or AMD surround group) of 3840x1080px, so you end up with two wide stretched virtual displays with 3840x1080px each in Windows afterwards. Each display group will represent its own projection stack level and has to be cabled that way.
2. Perform a camera based calibration for each stack level separately.
Start WINGS VIOSO and open the VIOSO Callibrator from the "Programs" menu in the main menu bar. As targets you will see your two "wide" displays as display compounds. Please make sure to set the correct split settings in the options for each of them. Perform a separate camera based calibration for each display compound. Do not close the calibrator program in between.
3. Combine the calibrations and export for WINGS VIOSO
Select "Stack compound calibrations" from the Calibration menu. After the calculation has been done, make sure that the "stacking mode" checkbox is selected. Activate the calibration with the "Preview" button and verify your stacked projection using an appropriate test image. If everything is satisfactory, go to File-Export and export as a .VWF file for WINGS VIOSO. Close the Calibrator.
4. Check screen settings in WINGS VIOSO and import calibration.
Using our example from above, make sure that you have two multidisplay outputs for your WINGS VIOSO screen that will have the display group resolution (3840x1080) and will have 100% vertical overlap. If using the project wizard, set up the screen as a 1x2 multidisplay configuration and select 1080px as vertical overlap. Please note that these resolutions do not represent the real world situation. The resolution and aspect ration of the content space will entirely be set by the VIOSO calibration process. Select "Multidisplay - VIOSO Calibration" from the WINGS menu and load the VWF file you saved before as a calibration for your WINGS screen.