metric rays are traced using the two
commands,<strong>FOB</strong> and </strong>RAY</strong>.
The <strong>FOB</strong> command is used to specify the location of
the current object point from which all subsequent rays are to be
traced. Input consists of the relative Y, X, and Z coordinates,
measured in the current object surface and in relative units of the
reference object heights. Reference object heights were input in the
current lens prescription using the <strong>SCY/SCX</strong> or
<strong> SCY FANG /