If a non-isometric aspect ratio is chosen, these functions will still draw
objects that appear to the viewer to be spheres. Use ellipse3d
to draw shapes that are spherical in the data scale.
When the scale is not isometric, the radius is measured in an average scale.
In this case the bounding box calculation is iterative, since rescaling the
plot changes the shape of the spheres in user-coordinate, which changes
the bounding box. Versions of rgl
prior to 0.92.802 did not do
this iterative adjustment.
If any coordinate or radius is NA
, the sphere is not plotted.
If a texture is used, its bitmap is wrapped around the
sphere, with the top edge at the maximum y coordinate,
and the left-right edges joined at the maximum in the
z coordinate, centred in x.