Overview
Project: Master Of None
Estimated Development Time: 8-10 hours
Lines Of Code: 250
Description: A data structure that can be used by a variety of systems to prioritize a list of objects based on established categories and the values attached to them.
Objective: Keep the structure generic.
Why I chose to use a Priority Helper : Making the priority helper was not something I designed, but rather a component of the cover system that pulled out and made generic enough to be used by almost any AI system.
Design and Development
There are 2 main components to the priority helper: Priority Sets and the Priority Handler. A Priority Set is the interface used by the user to signify how much they want different categories to be valued when processing the list of objects. The Priority Handler is the actual data structure that manages and eventually sorts before being returned to the user.
Once again I believe an example is the best way to show how powerful a mere data structure can be. In fact I'll be pulling directly from Master Of None, including the input values for each category.
In this example, the NPC is planning a "Cover Tactics" subgoal. If you haven't had a chance to look over "Action Planner" in the AI Technology page, this may be slightly confusing, but basically this subgoal is trying to figure out how the NPC is going to fight from cover.
Cover Tactics is currently trying to determine the safest, nearby cover spot. To do this, it uses the Priority Set that it already configured for defensive cover. The image below are what have been input into Priority Set.
Category signifies to the system handling the data that it wants that particular aspect to be evaluated.
Min/Max determines the value of each of the category.
When a system evaluates these object, it always turns their evaluated data into a float between 0 and 1.0. So when Distance was input at -4.0 min and 4.0 max, there is the potential that category could come back negative. If the distance to the cover spot is half as long as the possible max, then the category would input as 0.5, which is then converted to 0 by the Priority Handler. If the cover spot was nearby, then the category would be evaluated around 0.75, which is converted into 2.
There are two more optional properties that can be set.
One is called Inverted. It is category specific, and when set to true it will invert the value coming in, making 0.8 into 0.2.
The second optional propertyy is called a Note. A Note is for the entire Priority Set, and can be anything needed for a more specific evaluation. One of the more common Notes is weapon range when it comes to evaluating potential attack targets.
Back in the example, Cover Tactics sends this Priority Set to the cover system with a list of cover objects. The cover system has functions to handle every possible category, but only uses those functions if the category shows up in the Priority Set.
Each of the cover objects are then evaluated and given a value based on the category's Min/Max. Finally, the categories are added up and sorted from highest to lowest before being sent back to Cover Tactics.
Final Notes
As you can see, there isn't a whole lot to the Priority Helper, but the more I've worked with it the more I've seen how powerful it can be. The value of a specific object can change dramatically by simply altering its Priority Set, making it so easy to reuse the same code for entirely different behaviors.