this is a condensed form of a presentation going over a lot of the ai workings in my game Sor. for a more standard presentation viewing experience, refer to the PDF form of the presentation.


decisions, planning, personality

note: project is wip

  • everything in this project is highly wip

  • any amount of the bird planning architecture may change

  • sor is a cool game

    • more of a simulation than a game

  • we don't use capitalization and highlight unnecessarily

decision modeling

utility ai

  • how "useful" is an action?

  • given a list of considerations

    • score each consideration by running various appraisals

    • transform inputs on curves to score levels

    • scores are in the range [0, 1]

    • optional thresholds attached to considerations

      • score is 0 if score < threshold

example: eat food

  • consideration "eat"

    • appraisal "hunger"

      • a curve that sharply increases as energy percentage drops

    • appraisal "food availability"

      • discrete 0 or 1 for current availability of food

    • threshold 0.6

  • plans the "eat" objective on success

reasoner architecture

  • consideration

    • series of appraisals and an action

  • appraisal

    • function returning a score

  • reasoner

    • given a series of considerations, choose the "best"

      • the highest score is not necessarily the "best"

      • sometimes, to introduce unpredictability and variety, a fuzzy-decision strategy is used to choose between several similarly-scoring considerations


goal-oriented action planning (GOAP)

  • plan a sequence of actions to satisfy a goal

    • actions specify preconditions, postconditions and costs

    • goals are specified as a final postcondition

  • graph search for optimal path

    • find the lowest-cost series of actions that reach the goal

    • an algorithm like A* can be used to tune search with a heuristic

    • A* heuristics can be biased to affect the "quality" of a plan

example: obtain food

  • goal: satiety > TARGET_SATIETY

  • actions:

    • eat bean

      • precondition: existence of bean

      • postcondition: satiety += BEAN_ENERGY

      • cost: distance/time to obtain bean

    • visit tree

      • precondition: existence of tree

      • postcondition: satiety += BEAN_ENERGY * TREE_BEANS

      • cost: distance/time to reach tree

how birds think

real-time bird thinking

  • mind that runs a sense-think-act loop

    • a mind is associated with systems that can be run at different update rates

    • work offloaded to background threads

      • handle more computationally intensive planning

      • previous plans can be executed until new plans are available

  • sense

    • reads information from the environment

  • think

    • pick the most valuable objective and plan actions

  • act

    • carry out real-time adjusted plans

phase 1: select objective

  • use a reasoner to choose an objective

    • eat

      • get energy by consuming beans

    • explore

      • discover more of the map

    • defend

      • self-preservation by fight or flight

    • socialize

      • build opinion with other birds

phase 2: plan actions

  • map the objective to action planning model

    • the phase 1 objective chooses the relevant actions

    • current state of the model based on sensed input

    • goal state is determined by the objective and bird state

  • use GOAP planner to get the best sequence of actions

    • plan is a series of action nodes

    • each node contains an intermediate state of the model

interaction queue

  • map abstract action plan to virtual controller input

  • interaction plans represent queued actions in the world

    • target sources provide positional objectives

      • fixed locations such as trees

      • moving locations such as other birds or beans

    • approach types are used to keep distances

      • flocking via custom approaches on multiple birds

    • task plans represent physical actions

      • feed task involves distance tracking then feeding another bird

personality engine

original idea: lunch simulation

  • simulate people eating lunch at restaurants

  • each person has a personality

    • represented by the HEXACO model

      • 6-aspect model of human personality used in psychology

    • immutable values

  • traits can be calculated from a personality

    • traits describe a person's expected response to a situation

    • values influenced by different aspects of personality

    • since personality is fixed, trait values are also fixed

  • interaction effects based on participant traits

    • conversations between people can affect their opinions of each other

personality representation

  • personality values are stored as a vector

  • traits computed from personality and trait vectors

    • dot product for trait value in range [-1, 1]

  • interactions use a function of the trait value

    • the trait value is used to map along a curve

    • trait values are distributed around 0

      • represents the relative value to the baseline

bird personalities

  • personality aspects

    • anxiety

    • social awareness

    • emotionality

    • v1

  • common traits

    • loyalty

    • aggression

    • wariness

    • inquisitiveness

    • sociability

example: sociability trait

  • example bird personality (+0.8, 0.4)

    • high anxiety and medium social awareness

  • using the sociability trait (-0.1, 1.0)

  • sociability = 0.32

  • factored into an appraisal for a socialize consideration

  • used to adjust the opinion bonus for being fed

bird emotions

  • transient values based on recent interactions

    • emotions fade toward 0 with time at a fixed decay rate

  • can influence behavior to a lesser extent

    • traits provide primary influences on behavior

    • emotions can slightly shift the balance in either direction

    • recent actions can secondarily influence actions

  • cause different responses to the same stimuli

  • emotional sensitivity determined by traits

    • traits affect how much an action impacts emotions


fun birds

  • once i figure out how to make birds fun

    • i will let you know

  • the game runs on windows, mac, and linux