Graph Drawing System Operations
The Initial Button
When the system is first started, e.g., through a page, there is a single
button Show which shows the main graph drawing window. When
this button is pressed it changes into Hide, which naturally
hides the graph drawing window.
The User Operations
When in the graph window the following operations are supported:
- Left-Click (and Drag) Move vertices around, with the
edges pulling them back like rubber bands.
- Shift Left-Click This fixes the location of
a vertex, so it does not jitter.
- Double-Click This changes the graph to display
only the localized region around the clicked vertex, i.e. only those
vertexs connected to the clicked one. To go back, use the
Back button.
- Shift Double-Click This changes the graph so that
several vertices are grouped into one vertex. Either all vertices within a
certain distance are grouped, or, if there are some vertices which are
fixed in place, the set of fixed vertices is grouped.
- Ctrl Left-Click (and Drag) In the relaxed embedding this
adjusts the lengths of the edges.
- Blue Button Pressing the blue button in the lower right
corner of the graph window shows/hides the control window, described
below.
The Embeddings
The following embeddings are supported:
- Stable stabilizes everything so that nothing moves.
- Relax does a weak-repulsion layout of the graph
with fixed length edges.
- Random puts the vertices on random static points.
- Circular puts the vertices on static points
on the circumference of a 2D circle (random in Z).
- Barycentric positions the vertices by solving a
linear system, given a set of previously placed vertices. The set
of previously placed vertices can be either a cycle from the graph
or the set of vertices fixed in place.
- ForceDirect is similar to that above, but is a more
conventional implementation without some heuristics which are used
above.
- Linear does a hierarchical layout of the vertices.
The Controls
The various controls in the control window are the following:
- Embeddings, the upper left selector, allows selection of
one of the above embeddings.
- 3D / 2D allows or disallows Z values
other than 0 for vertices.
- Back goes back to a previous localization
or grouping (see above).
- Rotate Shows or hides the rotation control window, in
which there are three sliders, X, Y,
and Z which control rotation around the tree axes.
- Area Constant Control the constant multiplier of the
area of the graph drawing space.
Usually allows you to control the size of the graph, shrinking or
expanding the embedding.
- Localization Depth Select how deep a double-click
localization or grouping is, e.g., if it is 2, all vertices within depth
2 of the selected vertex are used in the localization or grouping.
- Minimum Temperature Select the minimum possible
temperature of an annealing process. This allows you to ``turn up
the heat'' on a force-directed embedding.
- Attraction Constant and Exponent In the force-directed
embedding the attraction between adjacent vertices follows the formula
f(d) = c/k * d^{e} where c and e are the
constant and exponent controlled by these sliders.
- Repulsion Constant and Exponent In the force-directed
embedding the repulsion between any two vertices follows the formula
f(d) = -c*k^{2} / d^{e} where c
and e are the constant and exponent controlled by these sliders.
- Current Temperature This field shows the current temperature of
a force-directed placement, or the timestep of the hierarchical layout.