Ch 7.2: Performing Ch 7.2: Performing Qualitative Terrain Analysis Qualitative Terrain Analysis

in in MoO3MoO3

What is It?What is It?

Analysis based on fundamental Analysis based on fundamental differences between types of locationsdifferences between types of locationsAreas visible to opponentsAreas visible to opponentsAreas that are impassableAreas that are impassableAreas vulnerable to enemy fireAreas vulnerable to enemy fire

Use information to identify strategic areas Use information to identify strategic areas (minimize defensive needs, maximize (minimize defensive needs, maximize territorial control)territorial control)

BackgroundBackground

Master of Orion 3Master of Orion 3 ( (MoO3MoO3))Turn-based strategy gameTurn-based strategy gameBuild empires and vie for control of the Build empires and vie for control of the

galaxygalaxyUp to 256 star systems connected by star Up to 256 star systems connected by star

laneslanesUp to 8 planets/star systemUp to 8 planets/star systemGoal – provide good measure of strategic Goal – provide good measure of strategic

value of star’s locationvalue of star’s location

Strategic QualitiesStrategic Qualities

Stars through which all ships from the Stars through which all ships from the outside must passoutside must pass

Stars that increase controlled territory, Stars that increase controlled territory, increase # of stars inside bordersincrease # of stars inside borders

Make sure that enemy stars aren’t put Make sure that enemy stars aren’t put inside bordersinside borders

Minimize # of threatened starsMinimize # of threatened stars

Free SpacesFree Spaces

Large open spaces containing strategically Large open spaces containing strategically valuable locations (resources, cities, etc.)valuable locations (resources, cities, etc.)

Stars in Stars in MoO3MoO3

Voronoi diagram

CorridorsCorridors

Connecting passages between free Connecting passages between free spacesspaces

1-dimensional entity1-dimensional entityConnects exactly 2 free spacesConnects exactly 2 free spacesNo valuable resources in them, only No valuable resources in them, only

strategic b/c of the free spaces they strategic b/c of the free spaces they connectconnect

Star lanes in Star lanes in MoO3MoO3

MoO3MoO3 Example Example

Analyzing the TerrainAnalyzing the Terrain

““inside our borders” – every path away inside our borders” – every path away from star arrives at one of our colonies from star arrives at one of our colonies without passing through unexplored starswithout passing through unexplored stars

Limit # of star lanes traversed for aboveLimit # of star lanes traversed for above ““threatened” – a star outside our borders threatened” – a star outside our borders

or connected to another civilization’s or connected to another civilization’s colony via an unprotected pathcolony via an unprotected path

Sample GalaxySample Galaxy

Selecting New ColoniesSelecting New Colonies

Determine possible planets to colonize Determine possible planets to colonize and assign each a priorityand assign each a priority

Assign probabilities to each based on its Assign probabilities to each based on its prioritypriority

Randomly select oneRandomly select onePriority = strategic modifiers * economic Priority = strategic modifiers * economic

valuevalueEliminate planets whose priority is <1/2 Eliminate planets whose priority is <1/2

the priority of the best choicethe priority of the best choice

Strategic ModifiersStrategic Modifiers

Base multiplier = 1.0Base multiplier = 1.0 If we already have 1+ colonies at star:If we already have 1+ colonies at star:

And another civ. has a colony there, multiply by 1.5And another civ. has a colony there, multiply by 1.5 Else, multiply by 0.8Else, multiply by 0.8

Else, if another civ. has a claim there, avoid; Else, if another civ. has a claim there, avoid; multiply by 0.3multiply by 0.3

Else, if in our borders, multiply by 0.9Else, if in our borders, multiply by 0.9 Else, it is unclaimed and outside borders, so use Else, it is unclaimed and outside borders, so use

the next set of modifiersthe next set of modifiers

Strategic Modifiers (cont.)Strategic Modifiers (cont.)

Multiply by 0.5 (new vulnerability)Multiply by 0.5 (new vulnerability) Multiply by 0.3 for each enemy colony that would Multiply by 0.3 for each enemy colony that would

be in our bordersbe in our borders If none, multiply by 1 plus:If none, multiply by 1 plus:

.25 for each unclaimed star that would be inside our .25 for each unclaimed star that would be inside our new bordersnew borders

1 for each of our systems that would be inside our 1 for each of our systems that would be inside our new bordersnew borders

1 if our homeworld would become an interior system1 if our homeworld would become an interior system Combine all modifiers and square themCombine all modifiers and square them

ResultsResults

Early on, AIs colonize primarily systems Early on, AIs colonize primarily systems which give new, unthreatened territorywhich give new, unthreatened territory

Later, colonize better planets inside Later, colonize better planets inside bordersborders

Intermingling begins as options run lowIntermingling begins as options run lowRandomness of moves keeps AI from Randomness of moves keeps AI from

being “perfect”being “perfect”

Player ResponsePlayer Response

Option in game to allow AI to select Option in game to allow AI to select colonies for playerscolonies for players

Players confused by how AI acted, thought Players confused by how AI acted, thought it was too expansionist (would ignore it was too expansionist (would ignore “juicy” colonies in interior systems)“juicy” colonies in interior systems)

Thus, strategic portion of the colonization Thus, strategic portion of the colonization AI had to be turned off for player!AI had to be turned off for player!

Other Uses of Terrain AnalysisOther Uses of Terrain Analysis

Production choicesProduction choices Boost priority of local defenses on planets in Boost priority of local defenses on planets in

threatened systemsthreatened systems Allowed the AI to use resources more efficientlyAllowed the AI to use resources more efficiently

Selection of targets for attacksSelection of targets for attacks Priority given to interior enemy planetsPriority given to interior enemy planets Player criticized lack of ambition of AIPlayer criticized lack of ambition of AI

Diplomatic AI (not implemented)Diplomatic AI (not implemented) Express displeasure when dispute is detectedExpress displeasure when dispute is detected Less contentious when no disputesLess contentious when no disputes

Applications in Other GamesApplications in Other Games

Have AI defend threatened corridors Have AI defend threatened corridors instead of the free spaces connected by instead of the free spaces connected by them (faster response, choke holds)them (faster response, choke holds)

Place scouts down each corridor (advance Place scouts down each corridor (advance warning, one force to defend multiple warning, one force to defend multiple entrances)entrances)

On the offensive, send multiple forces On the offensive, send multiple forces down several corridors (split up defenders)down several corridors (split up defenders)

Proof of AI’s EffectivenessProof of AI’s Effectiveness

SourcesSources

Dill, Kevin, “Performing Qualitative Terrain Analysis in Dill, Kevin, “Performing Qualitative Terrain Analysis in Master of Orion 3Master of Orion 3,” ,” AI Game Programming Wisdom 2AI Game Programming Wisdom 2..

Voronoi diagram - Voronoi diagram - http://www.cs.sunysb.edu/~algorith/files/voronoi-diagramhttp://www.cs.sunysb.edu/~algorith/files/voronoi-diagrams.shtmls.shtml

MoO3MoO3 screenshot - screenshot - http://www.rakrent.com/rtsc/html/moo3.htmhttp://www.rakrent.com/rtsc/html/moo3.htm

StarcraftStarcraft screenshot - screenshot - http://wehate.org/img/starcraft/lolzergrush-1-1.jpghttp://wehate.org/img/starcraft/lolzergrush-1-1.jpg