CSE4MOD Bot Navigation and Karma

1. CSE4MODBot Navigation and Karma Paul Taylor 2009

2. Unreal 4 • For the Next, Next Generation Consoles • Due around 2012 http://arstechnica.com/gaming/news/2008/07/epic-games-unreal-engine-4-ready-in-2012.ars

3. 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’sPhysX • Now owned and hardware supported by Nvidia!

4. 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)

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

6. 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 ??

7. 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

8. 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

9. 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

10. 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

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

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

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

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

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

16. 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

17. Collision Primitives • MCDBX • MCDSP • MCDCY • MCDCX

18. 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

19. Viewing Collisions In UnrealEd

20. 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

21. KHinge • HT_Normal • HT_Springy • HT_Motor • HT_Controlled • Motor + Specified Destination Angle Hinges are Triggerable

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

23. 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

24. 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

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

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

27. 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)

28. 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.

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

30. 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

31. 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)

32. 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.