anchor.diff:  Direction assigners have a `kind` of `:direction`, and their
   `target-id` is a keyword of the form `:i68` which would represent an
   assignment to the fixture or head with ID 68. The assignment values
  -they return are either a `javax.vecmath.Vector3d`, a dynamic parameter
  -which will resolve to a `Vector3d` object, or `nil`, meaning no
  -assignment should take place.
  +they return are either a `javax.vecmath.Vector3d`, a
  +<<parameters#direction-parameters,dynamic parameter>> which will
  +resolve to a `Vector3d` object, or `nil`, meaning no assignment should
  +take place.
   
   When the assignment is resolved, the vector indicates the direction in
   the <<show_space#show-space,frame of reference of the show>> to aim
  
positive.code: head's `:strobe`
  https://github.com/brunchboy/afterglow/blob/master/doc/fixture_definitions.adoc#function-specifications[function].
  The assignment values they return are either a percentage value, a
  dynamic parameter which will resolve to a percentage value, or `nil`,
  meaning no assignment should take place.
  
  When the assignment is resolved,
  http://deepsymmetry.org/afterglow/doc/afterglow.effects.channel.html#var-function-assignment-resolver[function-assignment-resolver]
  
negative.code: Aim Assigners
  ^^^^^^^^^^^^^
  
  Aim assigners have a `kind` of `:aim`, and their `target-id` is a
  keyword of the form `:i17` which would represent an assignment to the
  fixture or head with ID 17. The assignment values they return are
  either a `javax.vecmath.Point3d`, a
  <<parameters#aim-parameters,dynamic parameter>> which will resolve to
  a `Point3d` object, or `nil`, meaning no assignment should take place.
  
  When the assignment is resolved, the point identifies the precise
  location in the <<show_space#show-space,frame of reference of the
  