Four different types of tick mark layouts are possible.
This description applies to the X axis; other axes are similar:
If xat
is not NULL
, the ticks are set up at custom positions.
If xunit
is numeric but not zero, it defines the tick mark base. If
it is "pretty"
(the default in bbox3d
), ticks are set at pretty
locations.
If xlen
is not zero, it specifies the number of ticks
(a suggestion if xunit
is "pretty"
).
The first color specifies the bounding box, while the second one specifies the tick mark and font color.
bbox3d
defaults to pretty
locations for the axis labels and a slightly larger
box, whereas rgl.bbox
covers the exact range.
axes3d
offers more flexibility in the specification of the axes, but
they are static, unlike those drawn by bbox3d
.