> topic 3: DataReferenceImpl
> I would like to create a line with one anchored point *and of constant
> length*, basically a ray which the user can grab the outer end to trace
> a circle.
> The only examples I have seen so far are a line which uses one
> "northing" point (Ugo's example in Section 6.4) and a line defined by
> two moveable points.
> Can I create such a line as described?
The visad/benjamin/Galaxy.java does just this for a 3-D
point and a 3-D line. The moveable "red" point is a
RealTuple rendered using a DirectManipulationRendererJ3D.
It's DataReferenceImpl, named red_cursor_ref, triggers
a CellImpl named red_cursor_cell, which computes a line
from the red_cursor to our Sun as a Gridded3DSet named
line_to_sol. red_cursor_cell does some other things that
you can ignore.