CSE4MOD Bot Navigation and Karma Paul Taylor 2009

Unreal 4 For the Next, Next Generation Consoles – Due around games-unreal-engine-4-ready-in-2012.ars

Karma Karma was the Physics Engine in Unreal. Used from UT2003 & Unreal Championship Until UT2K4 Basically used on all versions of the Unreal 2.x Engine As of Unreal3 Karma has been dropped in favour of Ageia’s PhysX – Now owned and hardware supported by Nvidia!

Access to Karma To use Karma you need to have a special actor – KActor – This class + children can react dynamically with the environment – In the movement category the Physics property is set to PHYS_Karma. – How objects react is stored in the KParams property (in the Karma category)

Surfaces That Interact All surfaces in the Unreal Level have a variable bBlockKarma

Multiplayer = Failure Karma does not replicate. The Physics that reacts to your explosions etc, will not replicate as Karma is local only ?? One of the reasons Karma was dropped ??

Static Mesh Performance UseSimpleKaramaCollisions This is the complicated way to use Karma – You need to have a Collision model for your mesh – Otherwise you set it to false, and Karma will use every Polygon in your static mesh – = Slow!!! – If you set it to true without a Collision Mesh

Enabling Karma Karma doesn’t get enabled till enough force is applied to an Actor. – This is not a bug, it’s an optimisation feature. – In Kparams you can alter KStartEnabled

Karma Parameters bDestroyOnWorldPenetrate bDoSafeTime – Extra safe checks on world penetration bHighDetailOnly – Removes actions for lower machines bKAllowRotate – Allows z-axis rotation Only affects actors with KStayUpright set

bKDoubleTickRate – Increases the speed + Accuracy of physics calculations but should be set Uniform to any objects which MAY collide bKNonSphericalInertia – Calculate Inertia NOT based on a sphere bKStayUpright – Duh! = zAxis

KActorGravScale – Gravity Multiplier per-actor KAngularDamping – Rotational Drag Kboyancy – 0 = ignored – 1 = float mid water – >1 = float to surface

KLinearDamping – Translational Drag Kmass – Relative to the volume of the Karma Primitives KMaxAngularSpeed – Max speed of actor rotating KMaxSpeed – Plain old speed

KStartAngVel (XYZ) KStartEnabled KStartLinVel KVelDropBelowThreshold – Causes an Event StayUprightStiffness – Springiness to stay upright StayUprightDamping

Kfriction – 1=Full friction – 0 = no friction KImpactThreshold – Calls an event Krestitution – Bouncyness 0 = None 1 = perfect energy retention

bKDoConvulsions – Allows RagDolls to convulse! At interval: KConvulseSpacing bRubbery – Makes Ragdolls bend and flex dramatically Kskeleton – This sets the ragdoll skeleton to be used.

KCOMOffset – Centre of mass offset (XYZ) KInertiaTensor – 6 variables, 0 3 and 5 are important 0 = ease of roll, changes with Kmass and Drawscale 3 = ease of pitch 5 = ease of yaw

Collision Primitives MCDBX MCDSP MCDCY MCDCX

Collision Primitive Prefixes MCDBX - Box MCDSP - Sphere MCDCY - Cylinder MCDCX – Convex Mesh These will allow a static mesh to be imported with the collision already set

Viewing Collisions In UnrealEd

Constraints So far we have covered free objects Constraints will let us tie objects together – The Three Constraint actors – KBSJoint Ball-Socket Joint – KConeLimit This applies to existing joints and seves to limit rotation – KHinge

KHinge HT_Normal HT_Springy HT_Motor HT_Controlled – Motor + Specified Destination Angle Hinges are Triggerable

Ragdolls and Complex Physics KAT The Karma Authoring Tool Karma Workspaces And Karma Assets

Maya -> KAT -> Unreal Objects are created in Maya with Joints – Exported with axTools to the Unreal PSK format KAT opens the.PSX and can then be used to create the.KA file. – You must copy the.AK into the KarmaData folder of UT. – Then set the KSkeleton variable of your object

Bot Navigation and AI basics Bots navigate primarily through the Navigation Path network The engine uses the A* path-finding algorithm to navigate from X to Y

Storing Paths LevelInfo class contains var const NavigationPoint NavigationPointList; The Bot Brains come from Bot.uc in the UnrealGame Package. Yes the original Unreal Package (UT). ~c1994 TeamAI again from UnrealGame

Bot.uc 260 Functions 24 events derives a lot of code from Controller.uc

Path Colours White – Very Wide Green – Large NPCs Blue – Cramped decreased game flow Purple – Lift, Teleporters and Jump Pads Light Purple – Ladder Yellow – Forced Paths Red – Proscribed Paths (Inverse of Forced)

Order of preference Bots will usually take White, then Green, then blue, but the true answer is hidden in the navigation code Bots navigate by attaching a cost to every action. – This allows you to entice them into blue paths with goodies.

Remember your console! Navigation Debuging: ShowDebug Viewclass <> ReviewJumpSpots - Spawns a bot and forces it to attempt various jump types on every jump spot in your level. Limits: – Transloc – Combo – Jump – LowGrav

ShowAI – AI debugging ViewBot – cycles bots ViewFlag – CTF Debugging SoakBots – When errors happen bots will pause the game Rememberspot Used by showdebug to show a white line directly, and if possible green lines following the navigation points

Jump Pads and Teleporters JumpSpot points act as a Jump Destination, bots will jump TO this point, not from it! – JumpSpot Properties bForceDoubleJump bDodgeUp bForceDoubleJumping – no check on success of a jump bNeverImpactJump – disables shield jumping bNoLowGrav – not used in low G bOnlyTranslocator TranslocTargetTag – set a target for using the TransLocator TranslocZoffset – Adjusts bot aiming up / down (z)

Doorways The Door actor acts as a navigation point. – If you have a simple actor as your door, you just need to set bPathColliding to false.