Hinge lets you rotate copies of a
polyhedron around edges of itself to build
up constructions in space.  It is an
example of a program that interacts with
geomview, the Geometry Center's 3D viewing
program.  Its main purpose is to demonstrate
some capabilities of geomview.

To move the construction around in the
graphics window, hold the left mouse button
down and drag the mouse.  If you let go of
the button while moving the mouse, the motion
will continue.  The type of motion is
determined by the selected icon in the
"Tools" panel; to change actions just click
on one of these icons.

Start by clicking the right mouse button on
an edge to select it.  Then click the right
mouse button on an adjacent face to rotate
the object through that face.  You may select
another edge at any time by clicking the
right mouse button on it.

You may load an alternate polyheron via the
"File" button.  Nice objects to try are:

  in Euclidean space      in hyperbolic space

          HingeCube                HingeDodec
          HingeTetra
          HingeDiamond
          HingeTriangle
          HingeLongcube

NOTES:

Double-clicking the right mouse button sets
geomview's notion of the current mouse
target object.  In most cases with Hinge
you want the current target to be the
entire world.  If you accidentally move an
individual object you may reset it by
hitting the 'w' key, or 'W' to reset
everything.  Then double-click on the
background to set the mouse target back to
the world.

Hinge works with any geomview OFF object.
You may create your own objects in the OFF
format as described in oogl(5).  Type
"man 5 oogl" for details.

BUGS

Because of some limitations in the current
version of geomview, Hinge sometimes does
not recognize that you are pointing at a
certain edge or face.  This usually happens
with polyhedra having faces which are
nearly coplanar, or in hyperbolic space as
you get far away from the origin.  It does
not work at all with a polyhedron that has
two or more exactly coplanar faces.  This
limitation will disappear in a future
version.