The stemvertex and stemvertices qualifiers add a stem or stems to the rear of vertex lines drawn with a command. The syntax is:
\stemvertex<n>\drawvertex... \stemvertices\drawvertex...where
<n>
is the number of the vertex line to be stemmed.
stemvertices stems all of the lines. Theses commands remain in effect only
for the current . For example
\stemvertex2\drawvertex\photon[\E 3](\Xone,\Yone)[6] \global\stemlength=1415 \stemvertices\drawvertex\gluon[\SW 4](0,0)[4]will draw a three-photon vertex with a stem of standard length on the second line (in the NE direction) and a four-gluon vertex with stems of length 1415 on each of the four lines. Note that the stemlength is not reset until the entire vertex has been completed. To stem just lines two and four one would have written
\global\stemlength=1415 \stemvertex2\stemvertex4\drawvertex\gluon[\SW 4](0,0)[4]and so forth. In this case vertexonex, vertexoney refer to the end of the stem and there is no easy way of marking the end of a given line sans stem. stemvertex may be used in conjunction with vertexlink and vertexcap. As an exercise try to produce: