This adds mathematical lines to a scene. Their intersection with the current
bounding box will be drawn.

`abclines3d(x, y = NULL, z = NULL, a, b = NULL, c = NULL, ...)`

## Arguments

- x, y, z
Coordinates of points through which each line passes.

- a, b, c
Coordinates of the direction vectors for the lines.

- ...
Material properties.

## Details

Draws the segment of a line that intersects the current
bounding box of the scene using the parametrization
\( (x, y, z) + (a, b, c) * s \) where \(s\) is a real number.

Any reasonable way of defining the
coordinates `x, y, z`

and `a, b, c`

is acceptable.
See the function `xyz.coords`

for details.

## Value

A shape ID of the object is returned invisibly.

## See also

`planes3d`

for mathematical planes.

`segments3d`

draws sections of lines that
do not adapt to the bounding box.