Psychtoolbox>Screen.{mex*} subfunction

Select the target buffer for drawing commands in stereo display mode and or
return the current/old buffer selection in ‘currentbuffer’.
This function only applies to stereo mode, it does nothing in mono mode.
“windowPtr” is the pointer to the onscreen stereo window. “bufferid” (optional)
is either == 0 for selecting the left-eye buffer or == 1 for selecting the
right-eye buffer. You need to call this command after each Screen(‘Flip’)
command or after drawing to an offscreen window again in order to reestablish
your selection of draw buffer, otherwise the results of drawing operations will
be undefined and most probably not what you want.
“param1” (optional) a parameter whose meaning depends on the active stereo mode:
In stereoModes 1 and 11 (frame sequential stereo) it allows to select if
stimulus onset should happen in an even video refresh interval (value 0) or in
an odd interval (value 1). Even and odd intervals correspond to either left- or
right-eye view, so this allows to choose if you want to have stimulus onset on
left eye or right eye.
If you want to use a stereo display mode, we recommend enabling the imaging
pipeline as well. The imaging pipeline will only work with recent hardware, but
it allows for more reliable stereo operation especially when using low-level
OpenGL for real 3D drawing. It also allows to parameterize aspects of stereo
presentation, e.g., gains and other settings of anaglyph stereo.

###See also: OpenWindow Flip