There used to be three attributes, given in the same units (only ratios where used), eyeSeparation, viewDistance (distance to the screen), and screenWidth (the idea was to scale it to the actual window width, but that was never done). The default values were given in inches: 2.0, 30.0, and and 13.0, respectively. The effective field of view was just under 25 degrees. Now, there is an explicit fieldOfView attribute, because chimera maintains the field of view when resizing the graphics window. Of the original three attributes, only eyeSeparation remains, and it is given in millimeters, and the latter two are replaced with screenDistance and windowWidth. The windowWidth value is automatically computed when the graphics window is resized which in turn adjusts the screenDistance based on the field of view. If the screenDistance is explicitly set, then the field of view angle is recomputed. Defaults for the new values, are 50.8 mm for the eyeSeparation, and 25 degrees for the fieldOfView. - Greg