Begin and End require one state variable with eleven values: one
value for each of the ten possible Begin / End objects, and one
other value indicating that no Begin / End object is being
processed. The two relevant commands are void Begin ( enum mode
) ; void End ( void ) ; There is no limit on the number of
vertices that may be specified between a Begin and an End .
Points. A series of individual points may be specified by
calling Begin with an argument value of POINTS. No special state
need be kept between Begin and End in this case, since each
point is independent of previous and following points. Line
Strips. A series of one or more connected line segments is
specified by enclosing a series of two or more endpoints within
a Begin / End pair when Begin is called with LINE_STRIP. In this
case, the first vertex specifies the first segment's start point
while the second vertex specifies the first segment's endpoint
and the second segment's start point. In general, the ith vertex
(for i > 1) specifies the beg