Triangulation Options

The Triangulation options panel controls how Regina works with 3-manifold triangulations.

The settings here are:

Default top-level tab

Specifies which tab in the triangulation viewer will first appear when you open a triangulation for viewing.

Default skeleton tab

Specifies which sub-tab will first appear when you switch to the triangulation skeleton tab.

Default algebra tab

Specifies which sub-tab will first appear when you switch to the triangulation algebra tab.

Surface calculation threshold

Determines when the information on the triangulation surfaces tab is computed. If the number of tetrahedra is at most the given value, then Regina will compute surface-related information automatically. If the number of tetrahedra is larger, then Regina will not compute this information until you manually press the Calculate button.

Note that 3-sphere and 3-ball recognition might use a slighly lower threshold than the one you set here. This is because they rely on almost normal surfaces, which in the worst-case scenario are much slower to work with than normal surfaces.

GAP executable

Tells Regina where to find GAP (Groups, Algorithms and Programming). GAP is not required by Regina, but if it is installed then it can help simplify group presentations.

This setting should be the name of the command that starts GAP (the default is simply “gap”). Regina will look for this command on the default search path. If you have installed GAP somewhere unusual then you will need to provide the full path to the executable (such as /usr/local/bin/gap).

Graphviz executable

Tells Regina where to find Graphviz. Graphviz is not required by Regina, but is needed if you wish to view face pairing graphs.

This setting should be the name of the command that Graphviz uses to draw undirected graphs. The default is “neato”, but you may use one of Graphviz' other drawing commands if you prefer (but note that the command is not called “graphviz”).

Again, Regina will look for this command on the default search path. If you have installed Graphviz somewhere unusual then you will need to provide the full path to the executable (such as /usr/local/bin/neato).

Tip

Regina works best with Graphviz version ≥ 2.0. If you have an ancient version (Graphviz 1.x) then you will need to set your Graphviz command to dot, not neato. This is because ancient versions of neato could not display multiple edges. Regina will check the version and warn you if you seem to be using the wrong command.