Section

Clicking this button initiates a section tour rather than a
projection tour.  That is, data points outside a distance (given
by the Eps scrollbar) from the projection plane are shown as
single pixel points.

Useful for identifying point clouds that have a hollow center.
For example, with this section facility it is easy to distinguish
between a data set containing points on the surface of a sphere,
from a data set containing points placed anywhere within a
sphere.