document bars better

[SteveDoyle2]

The manual defines wa, wb here (note that the quality is low in the manual)

and then doesn't use wa, wb (it calls them w1 and w2)

Furthermore, there it is unclear that wa/wb must be defined in the global coordinate system. It should be stated.

[SteveDoyle2]

v/wa/wb is also rectangular regardless of the coordinate system of GA/GB.

I'd also recommend renaming G1/G2 to GA/GB to be consistent with NX/MSC.