3D axis with control over tick length, tick angle and label position

Modification of rgl::axis3d() that adds three extra parameters, ticksize, labeldist and tickangle, to independently control the length of the axis tick marks, the distance between those tick marks and their labels, and the direction (within the plane orthogonal to the axis) in which both the tick marks and the labels are offset (see Details). Based on the solution proposed on Stack Overflow (see References).

Usage

axis3(
  edge,
  at = NULL,
  labels = TRUE,
  tick = TRUE,
  line = TRUE,
  pos = NULL,
  nticks = 5,
  ticksize = 0.05,
  tickangle = 45,
  labeldist = 3,
  ...
)

Arguments

edge: character string indicating the edge of the bounding box on which the axis is drawn (same format as in rgl::axis3d(), e.g. "z+-").
at: positions at which the tick marks are drawn; if NULL they are computed automatically with pretty().
labels: tick labels: logical, indicating whether to automatically label the axes or be omitted, or a vector of labels.
tick: logical; if TRUE the axis tick marks are drawn.
line: logical; if TRUE the axis line is drawn.
pos: optional position of the axis (see rgl::axis3d()).
nticks: approximate number of tick marks when at = NULL.
ticksize: length of the tick marks, as a fraction of the distance to the center of the scene's range.
tickangle: direction, in degrees, of the tick marks and labels within the plane orthogonal to the axis (e.g. 0 = along the first perpendicular coordinate, 90 = along the second one, 45 = towards the corner of the bounding box).
labeldist: distance between the tick marks and the labels, as a multiple of ticksize.
...: additional arguments passed to rgl::segments3d() and rgl::text3d().

Value

An rglId object (see rgl::lowlevel()) with the identifiers of the rgl elements added (line, tick marks and labels).

Details

By default (tickangle = 45), tick marks and labels are offset simultaneously along both coordinates perpendicular to the axis, towards the corresponding corner of the bounding box. The original behavior of axis3d() can be reproduced by setting tickangle = 45 and ticksize = 0.05 * sqrt(2) (the actual relative length of the tick marks).

References

Dominic Woolf (2013, Mar 23). R rgl distance between axis ticks and tick labels, Stack Overflow, https://stackoverflow.com/a/39299740/4303451.

Examples

library(rgl)
open3d() # Alternatively, use `new3d()` to clear the current device or open a new one
set.seed(1)
points3d(rnorm(100), rnorm(100), rnorm(100))
box3d()
# Draw several z axis at z+- and z--, with longer tick marks and
# labels closer to them than usual
axis3('z+-', ticksize = 0.5, labeldist = 1)
axis3('z+-', ticksize = 0.5, labeldist = 1, tickangle = 0)
axis3('z--', ticksize = 0.5, labeldist = 1, tickangle = 90)
3D plot