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User interaction and gameplay: User interaction and gameplay:
Scripting, AI, Physics, and BehaviorsScripting, AI, Physics, and Behaviors How are Players and NPCs controlled?
– Player’s interface– Scripting, AI, Physics, Behaviors
Determines gameplay
User InterfaceUser Interface
Manual (hardware)– Keyboard, mouse– Controller: analog mini-sticks, D-pad, analog buttons
Visual (screen display)– Active: menus, actions– Passive: status, HUDS– Score, lives, power, map, etc.– Split-screen, Whole screen, Invisible
User Interface:User Interface:UnrealUnreal
Controllers are non-physical actors which can be attached to a pawn to control its actions. – PlayerControllers are used by human players to control
pawns – AIControllers are used to implement the artificial
intelligence for the pawns they control. AIScripts can be associated with pawns placed in levels to modify
their AIControllers.
– ScriptedControllers can be used to make a pawn follow a scripted sequence
HUD– Uses 2D Canvas
User Interface:User Interface:VRML/X3DVRML/X3D
Sensor Nodes:– Drag Sensors:
TouchSensor, SphereSensor, PlaneSensor, etc.
– Proximity Sensor– Visibility Sensor
HUD Prototype– Moves 3D object along with viewpoint
ScriptingScripting
Native support the major concepts of time, state, properties, and networking (replication) which traditional programming languages don't address.
Safety– a pointerless environment with automatic garbage
collection – a safe client-side execution "sandbox
To enable rich, high level programming in terms of game objects and interactions rather than bits and pixels.
ScriptingScripting
Slow– C++ : 50M base language instructions per
second– UnrealScript: 2.5 million - a 20X performance
hit.
create animation-driven or time-driven code – Exploit latent functions (like FinishAnim and
Sleep)
Scripting: TimeScripting: Time
Most engines use Ticks– smallest unit of time in which all actors in a level are
updated. A tick typically takes between 1/100th to 1/10th of a second.
– limited only by CPU power; the faster machine, the lower the tick duration is.
Synchronous vs. Asynchronous Zero-time vs. Latent Event cascade
Scripting Examples: Scripting Examples: UnrealScriptUnrealScript
Actor (extends Object) is the parent class of all standalone game objects in Unreal. – The Actor class contains all of the functionality needed
for an actor to move around, interact with other actors, affect the environment, and do other useful game-related things.
Pawn (extends Actor) is the parent class of all creatures and players in Unreal which are capable of high-level AI and player controls.
Scripting Examples:Scripting Examples: UnrealScriptUnrealScript
function ModifyPlayer(Pawn Other) { local xPawn x; //x is a variable x = xPawn(Other); if (x != None) { x.MaxMultiJump = MultiJumpCount; x.MultiJumpBoost = MultiJumpBoost; x.Health = StartingHealth; x.HealthMax = MaximumHealth x.SuperHealthMax = SuperDuberMaximumHealth } }
Scripting Functionality: Scripting Functionality: World AwarenessWorld Awareness
native final function Actor Trace(HitLocation, HitNormal, TraceEnd, TraceStart, bTraceActors, Extent, Material) – casts a ray (aka "traces") into the world and returns what it
collides with first. Trace takes into account both this actor's collision properties and the collision properties of the objects Trace may hit.
Use Trigger– If a human controlled pawn is within the proximity of this
trigger and hits their USE key, it activates this trigger. VRML: Proximity, Collision, Gravity, Visibility nodes
Scripting Examples: Scripting Examples: Unreal Animation BlendingUnreal Animation Blending
Multiple animation channels/stages are used to blend into the animation track.
native final function AnimBlendParams( int Stage, BlendAlpha, InTime, OutTime, BoneName) – Before playing animation on any channel, you need to call
AnimBlendParams to set up that channel. Channels are blended in order starting at the base channel (channel 0) with higher channels blended on top.
– animations played on higher channels will mask animations played on lower channels, depending on the BlendAlpha of the higher animation channel and which bones the higher channel affects.
Scripting Examples: Scripting Examples: VRML Character ControlVRML Character Control
function mouseinput(val,t){
newrot.angle=calcangle(val.x,val.y);
touchval=val;
mlen=val.length();
if (mlen)
body2.rotation=newrot;
loco(mlen,t);
}
Scripting Examples:Scripting Examples: VRMLVRML
function keyinput(k,t){ if (k==106){ //jump stand.stopTime=walk.stopTime=run.stopTime=
jump.startTime=t; mlen=0; } if (k==119){ //w - walk mlen=1.5; } if (k==114){ //r- run mlen=2.9; }
if (k==104){ //h- halt mlen=0; }
Scripting Examples: Scripting Examples: VRMLVRML
if (k==38){ //up - faster mlen+= .2; } if (k==40){ //down - slower mlen-= .2; } if (k==39){ //right - turn newrot.angle= newrot.angle - .39; //16th of turn body2.rotation=newrot; } if (k==37){ //left- turn newrot.angle= newrot.angle + .39; body2.rotation=newrot; }
Scripting Examples: Scripting Examples: VRMLVRML
if (mlen<0) mlen=0;
touchval.x= mlen * Math.sin(newrot.angle);
touchval.y= mlen * Math.cos(-newrot.angle);
//print('ang='+newrot.angle);
//print('x='+touchval.x+',y='+touchval.y);
//print('mlen='+mlen);
loco(mlen,t);
}
Scripting Examples:Scripting Examples: VRMLVRML
function loco(mlen,t){ if (mlen<0.4){ //print('STOP'); stand.startTime=t; walk.stopTime=t; run.stopTime=t; }else if (mlen<2.9){ //print('WALK'); stand.stopTime=t; walk.startTime=t; run.stopTime=t; walk.cycleInterval = 4 - (1.0 * mlen); }else{ // print('RUN'); stand.stopTime=t; walk.stopTime=t; run.startTime=t; run.cycleInterval = 0.80 + (2.0/(mlen-1.9)); }}
Scripting Examples: Scripting Examples: VRMLVRML
function engine(val,time){ //advance position each frame
if (lasttime){
if (touchval.length()>=0.4) //not stopped
body.translation=
body.translation.add(touchval.multiply((time-
lasttime)*.5));
}
lastval=t;
}
Artificial IntelligenceArtificial Intelligence
Strong AI: the ability to perform activities normally thought to require intelligence, learning, and adapting.
Weak AI: specialized intelligent qualities.Deterministic- predictable
– Path PlanningNondeterministic – uncertainty
– NPC learning to adapt to fighting tactics
Artificial IntelligenceArtificial Intelligence
Chasing and Evading & Pattern movement Flocking Pathfinding
– A* algorithm Logic: Finite State Machines, Fuzzy Logic Probability
– Bayesian Adaptive
– Neural Networks– Genetic Algorithms
Artificial Intelligence:Artificial Intelligence:UnrealUnreal
AI Scripting allows enemies (and friends) to be controlled easily via external files that can be easily changed without map rebuilding.
Almost every important NPC (non player character) in Unreal II has a long and detailed script behind it controlling its behavious and actions under various conditions
Artificial Intelligence:Artificial Intelligence:UnrealUnreal
:MarinePatrolontrigger ChangeMarinePatrol gotolabel MarinePatrol2gotoactor PathNode0gotoactor PathNode1sleep 2gotolabel MarinePatrol
:MarinePatrol2ontrigger ChangeMarinePatrol gotolabel MarinePatrolgotoactor PathNode2gotoactor PathNode3sleep 2gotolabel MarinePatrol2
PhysicsPhysics
Collisions, gravity, falling, explosions, etc.– should be used selectively in your level so as not to
overwhelm the engine.
NOTE: Don’t confuse with: PYSICS-BASED ANIMATION
– the motion of the pawn determines what animation the pawn is playing.
– good for multiplayer situations because each client just looks at the motion of a given pawn to see what animation should be playing; no extra information needs to be transmitted.
Physics-based AnimationPhysics-based Animation
walking, running, crouch walking, swimming, flying, jumping, falling, landing, and idling.
functionality for playing arbitrary animations not based on movement.
Physics-based AnimationPhysics-based Animation// Play appropriate idle animationssimulated function PlayWaiting(){ if (Physics == PHYS_Falling) LoopAnim(FallingAnim, 1.0, 0.2); else if (Physics == PHYS_Flying) LoopAnim(FlyIdle, 1.0, 0.2); else if (Physics == PHYS_Swimming) LoopAnim(SwimIdle, 1.0, 0.2); else { if (bIsCrouched) LoopAnim(CrouchIdle, 1.0, 0.2); else LoopAnim(StandIdle, 1.0, 0.2); }}