Reference Points and Inner Origins

A macro of is based on an inner picture environment, which has an original point for drawing a structure and a set of sifted values. Suppose the definition of the macro contains an inner picture environment represented by

\begin{picture}( $\ell_{{x}}^{}$,$\ell_{{y}}^{}$)( sx, sy).
The point ( sx, sy) of the inner environment becomes the (0,0) point of the structure generated by the macro. This point is called the reference point of the macro in the present manual. On the other hand, the origin of the inner environment becames the ( - sx, - sy) point of the generated structure. It is called the inner origin of the macro.

For example, the command \cyclohexanev generates a skeleton,
\begin{xymspec} \cyclohexanev{} \end{xymspec}
in which the symbol o represents the inner origin and the symbol • represents a reference point. The macro \cyclohexanev is defined on the basis of an inner picture environment:

\begin{picture}(800, 800)(-400, -240).
As a result, the inner origin is referred to as the (400, 200) point of the resulting macro; and the inner (- 400, - 240) point is regarded as the new origin (0, 0), which is the reference point of the macro.

Each macro is characterized by the referece point and the inner origin, which are shown in a framed box beside the specification of the macro. The reference point and the inner origin of each macro are revealed by stating \origpttrue in the preamble of a manuscript. Then, they are printed with the symbols o and •; and the values of them appear on the display. For example, the above cyclohexane structure is typeset by the following statement: 

{\origpttrue
\begin{center}
\cyclohexanev{}
\end{center}}
or by an equivalent statement: 
\begin{xymspec}
\cyclohexanev{}
\end{xymspec}