Scripts and Behaviors
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Transcript Scripts and Behaviors
User interaction and gameplay:
Scripting, AI, Physics, and Behaviors
How are Players and NPCs controlled?
– Player’s interface
– Scripting, AI, Physics, Behaviors
Determines gameplay
User 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:
Unreal
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:
VRML/X3D
Sensor Nodes:
– Drag Sensors:
TouchSensor, SphereSensor, PlaneSensor, etc.
– Proximity Sensor
– Visibility Sensor
HUD Prototype
– Moves 3D object along with viewpoint
Scripting
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.
Scripting
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: 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:
UnrealScript
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 gamerelated 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:
UnrealScript
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:
World 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:
Unreal 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:
VRML 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:
VRML
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:
VRML
if (k==38){ //up - faster
mlen+= .2;
}
if (k==40){ //down - slower
mlen-= .2;
}
if (k==39){ //right - turn
newrot.angle= newrot.angle - .39;
body2.rotation=newrot;
}
if (k==37){ //left- turn
newrot.angle= newrot.angle + .39;
body2.rotation=newrot;
}
//16th of turn
Scripting Examples:
VRML
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:
VRML
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:
VRML
function engine(val,time){ //advance position each frame
if (lasttime){
if (touchval.length()>=0.4) //not stopped
body.translation=
body.translation.add(touchval.multiply((timelasttime)*.5));
}
lastval=t;
}
Artificial Intelligence
Strong AI: the ability to perform activities
normally thought to require intelligence,
learning, and adapting.
Weak AI: specialized intelligent qualities.
Deterministic- predictable
– Path Planning
Nondeterministic – uncertainty
– NPC learning to adapt to fighting tactics
Artificial 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:
Unreal
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:
Unreal
:MarinePatrol
ontrigger ChangeMarinePatrol gotolabel
MarinePatrol2
gotoactor PathNode0
gotoactor PathNode1
sleep 2
gotolabel MarinePatrol
:MarinePatrol2
ontrigger ChangeMarinePatrol gotolabel
MarinePatrol
gotoactor PathNode2
gotoactor PathNode3
sleep 2
gotolabel MarinePatrol2
Physics
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 Animation
walking, running, crouch walking,
swimming, flying, jumping, falling, landing,
and idling.
functionality for playing arbitrary
animations not based on movement.
Physics-based Animation
// Play appropriate idle animations
simulated 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);
}
}