interactively show rays traced on RADIANCE image under X11
takes a RADIANCE octree and a picture file
and displays it on an X11 window server using
The picture should have been created from a previous
calculation using the given octree.
Once the image is displayed, the user can use the 't' command of
to select points on the image to display the ray tree.
then produces a ray tree, which
will display (in red on a color screen).
option slows the display of each ray traced to make it easier to
follow the process.
option traces rays to light sources, which are normally hidden.
If the pointer is moved between the time 't' is pressed and
starts drawing rays, the rays will be displaced.