used to easily plug in different methods of smoothly varying a value over time.
git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@3834 542714f4-19e9-0310-aa3c-eee0fc999fb1
anything special for full-screen effects. They will be added to the interface
node and should set their z order to a positive value to render above the UI
and a negative value to render below it. Otherwise we don't really need to
impose a whole lot of structure.
git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@3798 542714f4-19e9-0310-aa3c-eee0fc999fb1
Michael Bayne