Racing Game A I By Austin Borden Qihan

Racing Game A. I. By Austin Borden, Qihan Long, and Jim Pratt

Defining the Racetrack �Sectors �Define on-track areas �Interfaces �Leading and trailing edges of a sector

Interfaces �Right/left edge �Driving line nodes: �Racing line �Overtaking line

Overtaking �When the A. I. car gets close to an opponent, it will change its driving line from racing to overtaking �Multiple overtaking lines possible �Burnout 1: 15

Sectors �Stores its distance from start, to finish line, and to other vehicles. �Path types �Terrain types �Walls �Hairpin turns �Brake-Throttle

Path Types �Defines the type of route ahead �Normal �Shortcut �Long route �Weapon pick-up route �Winding road �Drag strip �A. I. chooses route depending on current situation

Terrain Types �Adds another variable for A. I. to deal with �Rugged terrain �Slick �If a route is a shortcut and also rugged, only vehicles capable of traversing will choose this route �Terrain Traversing

Racetrack Definition Conclusion �The more information we provide, the less complex the A. I. system has to be

Racing A. I. Logic �Vehicles do not follow driving lines exactly, only guided by them �A. I. is supposed to emulate human input �Done by creating an A. I. controller

Basic A. I. Framework �Finite State Machines �Allows decision making �Fixed Time-Step �Ensures that AI reacts quickly always �Controls �float dx; //-1. 0 to 1. 0 for left to right steering �float dy; //-1. 0 to 1. 0 for max brake to max acceleration

Looking Ahead �Cars look ahead for obstacles and turns �The faster it’s moving, the further it looks to smooth path

Wall Avoidance �Position is predicted by using the current velocity and scaled by how far in the future we are predicting (seconds) �Correction amount is then applied to steering depending on which wall car is closest to �If predicted position is outside of sector, brakes are applied

Hairpin Turns �Looking too far ahead during a sharp turn will cause A. I. to cut corners �To fix this, car looks for hairpin flags and shortens the look ahead distance if flags are found

Under/Over-Steer �With simple physics cars can spin out due to over steering �Cars can also miss turns due to under steering �Based on sideways velocities of wheels

Steer Correction �Depending on over or under-steering, a correction value is added to the current steer value �Overcorrection is prevented by the understeer/oversteer range �Colin Mc. Rae Dirt 2

Catch-Up Logic �If A. I. is winning… �Limit A. I. ’s top speed in proportion to distance leading �Brake early for corners, accelerate slowly out of turns �Take long routes/ unstable terrain routes �Get worse weapons/ only target other A. I. �Opposite can be used if A. I. is trailing �Good way of making a race challenging for all skill levels �Diddy Kong Racing 1: 45 �Shadows of the Empire 5: 50

Catch Up Logic Case Study: Pure

The Rubber Band System

Racing Grouping in Pure

Difficulty Regulation �Powerful items �Intelligence modification �Similar Placing

Tuning the Car Handling �If each car has different characteristics, tuning the code can be time consuming.

Adjusting the Parameters �Assign each parameter with a minimum and maximum value. �Modify the parameter depending on whether the lap time decreases or increases. �Time for this process can be reduced by running the game as fast as possible.

Real Time Editing �Real Time Track Modification �An important tool in AI creation is the ability the change the track in real time. �Allows problems in the track to be quickly modified and tested. �User Control Overriding AI �Allows tester to take control when AI becomes stuck or incapable of navigating a certain part of the track. �Can be used to test the AI on specific parts of the track.

Layer Behavior �Reactionary system �Modular approach makes it easy �Multiple inputs for one output �Output contention system ultimately determines output �Layer Interactions: �Overriding �Internal states �Altering input for other layers

Example of Layers

Path Following Layer �Turning and speed dealt with separately �Attempt to keep car on line �Cornering regulation monitors speed �Corners and apex determined �Formulate max speed and braking zone distance �Dynamic according to current speed �Braking, cruise, full throttle

Tactical Racing Layer �Makes competitive racing choices (driver into a racer) �Analyzes situation and races accordingly �Find optimum road position �Generates new paths �Safe guards in place

Visual Perception � 8 eyes, 4 pairs �Determines speed and position of cars and environment �Determines desirability of current position based on environment and position of other cars

Fine Grain Avoidance Layer �Priority �Needed when cars want to occupy same space �Relative car position determines who yields �Prevents collisions by overriding �For passing, steering is moderated �For linear, speed is moderated

Determining Racing Lines �Problems with user made content �Track detail hard to take into account �Lines of minimum curvature are limiting, boring �Midway points across track �Forces used to smooth out sharp turns �Safe guards

Competitive AI Racing Under Open Street Conditions �Allows an AI controlled vehicle to traverse an random network of roads. �Finding the correct route to destination. �Calculating steering brake and throttle values.

Library Interface �Register. Route Interface �Holds a list of intersections and roads �Registers the path through the map �Called when entering a new route �Drive. Route Interface �Used on a lower level than the Register. Route interface �Calculates steering, throttle, and brakes �Used for driving forward, backing up, colliding, and stopping.

Navigating the City �Find the current location �Update the road cache �When a road is fully traversed, loads a new road into the cache. �Emulate all possible routes �Finds possible routes through the road

Avoiding obstacles �Check for obstacles after the route is calculated.

References � Champandard, Alex J. "Paris Game AI Conference '09: Highlights, Photos & Slides. " Game AI for Developers. Web. 24 Mar. 2010. <http: //aigamedev. com/open/coverage/paris 09 report/#session 13>. � "Gamasutra - Features - The Pure Advantage: Advanced Racing Game AI. " Gamasutra - The Art & Business of Making Games. Web. 24 Mar. 2010. <http: //www. gamasutra. com/view/feature/3920/the_pure_advant age_advanced_. php>. � "Mario Kart Wii: Those Damn Powerups. " Gamer. Bunny Speaks. Web. 24 Mar. 2010. <http: //gamerbunny. wordpress. com/2008/05/19/mario-kart-wiithose-damn-powerups/>. � Rabin, Steve. AI Game Programming Wisdom 2. Hingham, MA: Charles River Media, 2004. Print. � Rabin, Steve. AI Game Programming Wisdom. Hingham, Mass. : Charles River Media, 2007. Print. � Youtube. Web. 24 Mar. 2010. <http: //youtube. com>.

� Questions?