Sly 2:Game state: Difference between revisions

The '''DAG''' ('''D'''irected '''A'''cyclic '''G'''raph) is a data structure used to manage the current state of the game world. It was the subject of a 2005 GDC presentation by Bruce Oberg, the Principal Engineer at Sucker Punch.<ref>[https://www.gdcvault.com/play/1020295/The-Picture-Worth-a-Thousand The Picture Worth a Thousand Bugs] - YouTube, 3 April 2021 (archived from a 2005 GDC conference)</ref>

 

The DAG is a directed graph of nodes, where each node is called a ''task''. For instance, <tt>t1_follow_dmitri_on_streets</tt> is the task of tailing Dimitri in the "Follow Dimitri" job (the prefix <tt>t1</tt> indicates that it is a task in Episode 1, and <tt>follow</tt> is the codename for the "Follow Dimitri" job).

 

Each task has a ''state'', which is one of the following:

 

 

All tasks in the DAG start off as {{color|red|Unavailable}}. A task becomes {{color|dodgerblue|Available}} once all of its predecessors are {{color|limegreen|Complete}}. Tasks become {{color|limegreen|Complete}} through conditions being met in the level scripts, and tasks become {{color|gray|Final}} through missions.

 

At all times, every task ''before'' an Available task must be Complete or Final. Additionally, every task ''after'' an Available task must be unavailable. It is possible to ''force'' a task to a particular state, which propagates throughout the DAG to ensure those conditions are always met.

 

Tasks in the DAG can be grouped into ''missions''. A mission usually refers to a particular job in the game's story. For instance, <tt>m1_follow</tt>{{check}} is the job "Follow Dmitri" (the prefix <tt>m1</tt> indicates that it is a mission in Episode 1, and <tt>follow</tt> is the codename for the mission).

 

If a task belongs to a mission and the ''exit task'' in that mission is Completed, then all the tasks in that job become Final.

 

A task is considered a ''checkpoint task'' if it has some checkpoint data associated with it, including a particular character and location in the game world. When a checkpoint task becomes Available, that checkpoint is set as the ''latest'' checkpoint.

 

A rollback is when the game rewinds the DAG to an earlier state (such as when the player dies). This is accomplished by:

 

 

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