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Cover Me! Promoting MMO Player Interaction Through Advanced AI. Dave Mark President & Lead Designer Intrinsic Algorithm LLC. Dave Mark. President & Lead Designer of Intrinsic Algorithm LLC Game Studio AI Consulting Company Author of Behavioral Mathematics for Game AI
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Cover Me!Promoting MMO Player InteractionThrough Advanced AI Dave MarkPresident & Lead DesignerIntrinsic Algorithm LLC
Dave Mark • President & Lead Designer ofIntrinsic AlgorithmLLC • Game Studio • AI Consulting Company • Author of Behavioral Mathematics for Game AI • Co-founder ofAI Game Programmers Guild • Organizer and co-host of theAI Summit at GDC 2009
Premises/Disclaimers • WoW is a good game. • Not everyone wants to be like WoW. • Bad AI has its place in games. • Not everyone wants to have bad AI. • You are here because you are working on an MMO. • You are here because you want to know: • How good AI can make your game better • How to use AI in an MMO environment
What makes a game a game? “A game isa series of interesting choices.” - Sid Meier
In the beginning… • Early games were entirely played against the computer. • AI sucked • Choices were rudimentary • Problem-solving was simplistic.
1-Player Games w/Multi-player Component • People played against each other more than computer • Game won’t sell without multi-player • 1-player campaign often neglected • “I love Halo 3… but I’ve never played the campaign.”
Multiplayer Co-Op • People prefer playing with other people • Interactivity • Teamwork (AI allies still not up to par) • Solving problems together
The Draw of PvP • People prefer playing against other people • Difficulty of opponents • Adaptability of opponents • Dynamicity (e.g. the unexpected) • Solving problems together Replayability!
The Necessity of PvE • Beyond Game Mechanics • Environments • Weapons • Characters • World Immersion • Who is going to role-play the dragon? • The harmless little bunny? • The slime creature?
AI is Your World! Boring AI = Boring World Deep AI = Immersive World Repetitive AI = Monotonous World Dynamic AI = Dynamic World
PvP Difficult Adaptable Dynamic Necessitates ongoing problem-solving PvE Simple Rigid Predictable “Solve Once” and repeat PvP vs. PvE PvE • Difficult • Adaptable • Dynamic • Necessitates ongoing problem-solving So how do we do it?
Making PvE feel like PvP • Single-player games have been improving their AI to generate a PvP-like feel • What techniques can we import from single-player games into MMOs? • What effect does that have on the player’s individual experience? • What effect does that have on the players working together?
By Genre Shooter RPG Strategy By Concept Behavioral Tactical Strategic Simulation Economic AI Techniques
By Genre Shooter RPG Strategy By Concept Behavioral Tactical Strategic Simulation Economic AI Techniques Multiple vs. Multiple
Behavioral AI • How does the NPC make decisions? • Idle behaviors • When to attack • Who to attack • How to attack
When to Attack • Generating “Aggro” • Distance • Environment Threshold Triggers • Line of Sight • Well documented by the public • Attack happens when the player(s) want it to • Removes sense of enemy’s autonomy
Who to Attack • Nearest opponent • Strongest opponent • Well documented by the public • Attack is against whom the player(s) expect • Attack is against whom the player(s) want • Removes sense of enemy’s autonomy
How to Attack • Primary attack most of the time • After delay of x, use secondary attack • In given situation, use special attack • Well documented by the public • Attack happens how the player(s) expect it to • Removes sense of enemy’s dynamicity
Effect on the Players • On the Individual Player • Calculatable • Predictable • Boring • On the Group • No need for interaction • “Read the script…” • “Play your part…”
What is your reaction? • Want to pet • Want to meet • Just curious • Annoyed • Want to kick • Want to run screaming
Now what is your reaction? • Want to pet • Want to meet • Just curious • Annoyed • Want to kick • Want to run screaming
Same Model for All Agents Extreme Reactions
Varieties of Reactions • Differences Exist • Don’t need to know why • Need to simulate that difference do exist • Not completely random selection • Must be reasonable • Can be simulated with weighted randoms
Know when to walk away… • Design Decision: “Enemies don’t always fight to the death” • Enemies can sometimes retreat • Flat % chance • Is random… therefore looks random • Not realistic • Situational random • Based on circumstances • Circumstances are flexible and dynamic
Know when to walk away… How many on my side are still fighting? 8 1.6 5 How many of my enemies are still fighting?
Know when to walk away… PercentChance = (4 – Ratio)3 / (43)
Know when to walk away… PercentChance = (4 – Ratio)4 / (44) PercentChance = (4 – 1.6)4 / (44) PercentChance = 13%
Know when to walk away… How many on my side are still fighting? 7 1.4 5 How many of my enemies are still fighting?
Know when to walk away… PercentChance = (4 – Ratio)4 / (44) PercentChance = (4 – 1.4)4 / (44) PercentChance = 18%
Know when to walk away… PercentChance = (4 × Ratio)4 / (44)
Know when to walk away… PercentChance = ( ( MaxRatio – Ratio )k× MaxPct)/ (MaxRatio k )
Know when to walk away… ( ( 4 – Ratio )4 × 1.00 ) / ( 44 ) ( ( 4 – Ratio )6 × 0.75 ) / ( 46 ) ( ( 4 – Ratio )8 × 0.50 ) / ( 48 )
Know when to walk away… • Factors to Consider • Number of allies • Number of enemies • Proximity to Base • Strength of allies • Strength of enemies • My own health • Proximity of my leader
Know when to walk away… Numberof Allies Strengthof Allies Numberof Enemies Strengthof Enemies Allied Strength Enemy Strength Proximityto Leader My Health Proximityto Base Threat Ratio My Morale “Compartmentalized Confidence” Urgency Retreat %
How does this look to the players? • Enemies aren’t completely fearless • They are slightly unpredictable • They are still reasonable • Curiosity: “Where is he going?” • “If we show force, they might break and run.” • “If we back them up, they are more aggressive.” • We have to react to their reactions.
More than “Fight or Flight” • Fight normally • Flee • Charge
Fight Melee weapon Ranged weapon Special rare weapon Advance Press forward Berserker charge Retreat Fighting withdrawal Find Cover Organized pull back Flee in abject terror Surrender More than “Fight or Flight”
More than “Fight or Flight” “Normal” “Defensive” 21% 42%
How does this look to the players? • Not predictable • Reasonable • Causes us to have to react to his reaction
Target Selection • Who should I attack? • Closest enemy • Biggest threat (highest DPS) • Weakest link (least health) • Most valuable (healer helping the other enemies)