Ch 7.2: Performing Qualitative Terrain Analysis in MoO3

What is It? Analysis based on fundamental differences between types of locations Analysis based on fundamental differences between types of locations Areas visible to opponents Areas visible to opponents Areas that are impassable Areas that are impassable Areas vulnerable to enemy fire Areas vulnerable to enemy fire Use information to identify strategic areas (minimize defensive needs, maximize territorial control) Use information to identify strategic areas (minimize defensive needs, maximize territorial control)

Background Master of Orion 3 (MoO3) Master of Orion 3 (MoO3) Turn-based strategy game Turn-based strategy game Build empires and vie for control of the galaxy Build empires and vie for control of the galaxy Up to 256 star systems connected by star lanes Up to 256 star systems connected by star lanes Up to 8 planets/star system Up to 8 planets/star system Goal – provide good measure of strategic value of star’s location Goal – provide good measure of strategic value of star’s location

Strategic Qualities Stars through which all ships from the outside must pass Stars through which all ships from the outside must pass Stars that increase controlled territory, increase # of stars inside borders Stars that increase controlled territory, increase # of stars inside borders Make sure that enemy stars aren’t put inside borders Make sure that enemy stars aren’t put inside borders Minimize # of threatened stars Minimize # of threatened stars

Free Spaces Large open spaces containing strategically valuable locations (resources, cities, etc.) Large open spaces containing strategically valuable locations (resources, cities, etc.) Stars in MoO3 Stars in MoO3 Voronoi diagram

Corridors Connecting passages between free spaces Connecting passages between free spaces 1-dimensional entity 1-dimensional entity Connects exactly 2 free spaces Connects exactly 2 free spaces No valuable resources in them, only strategic b/c of the free spaces they connect No valuable resources in them, only strategic b/c of the free spaces they connect Star lanes in MoO3 Star lanes in MoO3

MoO3 Example

Analyzing the Terrain “inside our borders” – every path away from star arrives at one of our colonies without passing through unexplored stars “inside our borders” – every path away from star arrives at one of our colonies without passing through unexplored stars Limit # of star lanes traversed for above Limit # of star lanes traversed for above “threatened” – a star outside our borders or connected to another civilization’s colony via an unprotected path “threatened” – a star outside our borders or connected to another civilization’s colony via an unprotected path

Sample Galaxy

Selecting New Colonies Determine possible planets to colonize and assign each a priority Determine possible planets to colonize and assign each a priority Assign probabilities to each based on its priority Assign probabilities to each based on its priority Randomly select one Randomly select one Priority = strategic modifiers * economic value Priority = strategic modifiers * economic value Eliminate planets whose priority is <1/2 the priority of the best choice Eliminate planets whose priority is <1/2 the priority of the best choice

Strategic Modifiers Base multiplier = 1.0 Base 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 1.5 And another civ. has a colony there, multiply by 1.5 Else, multiply by 0.8 Else, multiply by 0.8 Else, if another civ. has a claim there, avoid; multiply by 0.3 Else, if another civ. has a claim there, avoid; multiply by 0.3 Else, if in our borders, multiply by 0.9 Else, if in our borders, multiply by 0.9 Else, it is unclaimed and outside borders, so use the next set of modifiers Else, it is unclaimed and outside borders, so use the next set of modifiers

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 be in our borders Multiply by 0.3 for each enemy colony that would be 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 new borders.25 for each unclaimed star that would be inside our new borders 1 for each of our systems that would be inside our new borders 1 for each of our systems that would be inside our new borders 1 if our homeworld would become an interior system 1 if our homeworld would become an interior system Combine all modifiers and square them Combine all modifiers and square them

Results Early on, AIs colonize primarily systems which give new, unthreatened territory Early on, AIs colonize primarily systems which give new, unthreatened territory Later, colonize better planets inside borders Later, colonize better planets inside borders Intermingling begins as options run low Intermingling begins as options run low Randomness of moves keeps AI from being “perfect” Randomness of moves keeps AI from being “perfect”

Player Response Option in game to allow AI to select colonies for players Option in game to allow AI to select colonies for players Players confused by how AI acted, thought it was too expansionist (would ignore “juicy” colonies in interior systems) Players confused by how AI acted, thought it was too expansionist (would ignore “juicy” colonies in interior systems) Thus, strategic portion of the colonization AI had to be turned off for player! Thus, strategic portion of the colonization AI had to be turned off for player!

Other Uses of Terrain Analysis Production choices Production choices Boost priority of local defenses on planets in threatened systems Boost priority of local defenses on planets in threatened systems Allowed the AI to use resources more efficiently Allowed the AI to use resources more efficiently Selection of targets for attacks Selection of targets for attacks Priority given to interior enemy planets Priority given to interior enemy planets Player criticized lack of ambition of AI Player criticized lack of ambition of AI Diplomatic AI (not implemented) Diplomatic AI (not implemented) Express displeasure when dispute is detected Express displeasure when dispute is detected Less contentious when no disputes Less contentious when no disputes

Applications in Other Games Have AI defend threatened corridors instead of the free spaces connected by them (faster response, choke holds) Have AI defend threatened corridors instead of the free spaces connected by them (faster response, choke holds) Place scouts down each corridor (advance warning, one force to defend multiple entrances) Place scouts down each corridor (advance warning, one force to defend multiple entrances) On the offensive, send multiple forces down several corridors (split up defenders) On the offensive, send multiple forces down several corridors (split up defenders)

Proof of AI’s Effectiveness

Sources Dill, Kevin, “Performing Qualitative Terrain Analysis in Master of Orion 3,” AI Game Programming Wisdom 2. Dill, Kevin, “Performing Qualitative Terrain Analysis in Master of Orion 3,” AI Game Programming Wisdom 2. Voronoi diagram - diagrams.shtml Voronoi diagram - diagrams.shtml diagrams.shtml diagrams.shtml MoO3 screenshot - MoO3 screenshot - Starcraft screenshot - Starcraft screenshot -