GDC09-JQGregory-StateScriptingInUncharted2.key

1. State-Based Scripting in
Jason Gregory
Generalist Programmer
Naughty Dog, Inc.

2. Agenda
Introduction to game scripting
•
Extending the game object model
•
State script syntax
•
Case studies from
•
Uncharted 2: Among Thieves
• Implementation discussion
• Summary and some tips
Game Developers Conference 2

3. Introduction to State Scripts
3

4. Brief History of State Scripts
• Script system on Uncharted: Drake’s Fortune originally developed
for in-game cinematics (IGCs)
• Evolved into general gameplay scripting system
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5. Brief History of State Scripts
• UDF IGC system revamped for heavy
use on Uncharted 2: Among Thieves
• Inspirations:
 GOAL language used on Crash and Jak series
 State objects from God of War engine
TM
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6. Why Script?
• Scripting languages used in games since Quake C
• Primary benefits of script:
 Takes pressure off engineering team
 Code becomes data—rapid iteration
 Empowers content creators
 Key enabler of mod community
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7. Why Script?
• Scripting languages used in games since Quake C
• Primary benefits of script: I feel
 Takes pressure off engineering team empowered!
 Code becomes data—rapid iteration
 Empowers content creators
 Key enabler of mod community
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8. Scripting Language Characteristics
• Two kinds of game scripting languages:
 data definition languages
 runtime languages
• Runtime scripting languages typically:
 interpreted by virtual machine (VM)
 simple and small—low overhead
 accessible to designers and other “non-programmers”
 powerful—one line of code = big impact
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9. Choice of Language
• At Naughty Dog, we make heavy use of both data definition
and runtime script
 Both based on PLT Scheme (a Lisp variant)
• Key benefits of Lisp-like languages:
 Easy to parse
 Data def and runtime code can be freely intermixed
 Powerful macro system—easy to define custom syntax
 Naughty Dog has a rich Lisp heritage—comfortable
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10. Choice of Language
• Of course you don’t have to use Lisp!
• Data definition languages:
 custom text format,
 Excel comma-separated values (.csv),
 XML, ...
• Runtime languages:
 Python, Lua, Pawn (Small C), OCaml, F#, ...
• Many popular engines already provide a scripting language:
 Quake C, UnrealScript, C# (XNA), ...
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11. Extending the Game Object Model
• Every game engine has some kind of game object model
 Defines all object types in game world
 Often (but not always) written in an object-oriented language
• Scripting language often used to extend the native object model
• Many ways to accomplish this...
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12. Game Object Model References
• Rob Fermier, “Creating a Data Driven Engine,” GDC, 2002
• Scott Bilas, “A Data-Driven Game Object System,” GDC, 2002
(http://www.drizzle.com/~scottb/gdc/game-objects.ppt)
• Alex Duran, “Building Object Systems: Features, Tradeoffs and
Pitfalls,” GDC, 2003
• Doug Church, “Object Systems,” presented at a game development
conference in Seoul, Korea, 2003
(http://chrishecker.com/images/6/6f/ObjSys.ppt)
• Jason Gregory, “Game Engine Architecture,” AK Peters, 2009
(http://gameenginebook.com)
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13. Unreal’s Approach
• UnrealScript tightly integrated with C++ object model
 Single-root class hierarchy with some add-on components
 Classes defined in UnrealScript (.uc)
 C++ header file (.h) automatically generated
 Implementation in C++ or entirely in UnrealScript
Pawn.h Actor
generate
Pawn.uc
...
Info Pawn Pickup
Pawn.cp
p
implement
...
Scout
implement
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14. Property-Centric / Componentized Designs
• Property-centric design used on Thief, Dungeon Siege, Age of
Mythology, Deus Ex 2 and others
 Game object just a unique id (UID)
 “Decorated” with various properties
(health, armor, weaponry, etc.)
 Property encapsulates data + behavior
Armor: Light
Health: 200
Object Weapon: BFG
(UID)
AI: PlayerAlly
Weapon: Pistol
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15. Uncharted Engine’s Object Model
• Uncharted class hierarchy:
 relatively shallow, single-root
 host of add-on components
Process
...
SsProcess DynLight
...
Character
...
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16. Uncharted Engine’s Object Model
• Uncharted class hierarchy:
 relatively shallow, single-root
Objects
 host of add-on components that update
over time
Process
...
SsProcess DynLight
...
Character
...
Game Developers Conference 14

17. Uncharted Engine’s Object Model
• Uncharted class hierarchy:
 relatively shallow, single-root
 host of add-on components Objects with
transform
Process
...
SsProcess DynLight
...
Character
...
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18. Uncharted Engine’s Object Model
• Uncharted class hierarchy:
 relatively shallow, single-root
 host of add-on components Base class
for all
characters
Process
...
SsProcess DynLight
...
Character
...
Game Developers Conference 14

19. Uncharted Engine’s Object Model
• Uncharted class hierarchy:
 relatively shallow, single-root
 host of add-on components Simple
animating
Process object
...
SsProcess DynLight
...
Character
...
Game Developers Conference 14

20. Uncharted Engine’s Object Model
• Uncharted class hierarchy:
 relatively shallow, single-root
 host of add-on components
Process
...
SsProcess DynLight
...
Character
Manages a
...
State Script
instance
Game Developers Conference 14

21. Uncharted Engine’s Object Model
• Uncharted class hierarchy:
 relatively shallow, single-root
 host of add-on components
Process
...
SsProcess DynLight
...
Character
Manages a
...
chunk of
running
script code
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22. Uncharted Engine’s Object Model
• Uncharted class hierarchy:
 relatively shallow, single-root
 host of add-on components
Process
SsProcess
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23. Uncharted Engine’s Object Model
• Uncharted class hierarchy:
 relatively shallow, single-root
 host of add-on components
Process
SsProcess
SsInstance
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24. Uncharted Engine’s Object Model
• Uncharted class hierarchy:
 relatively shallow, single-root
 host of add-on components
Process
...
AnimContr
SsInstance DrawContr
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25. Charter
• World editor for
Uncharted is called
Charter
 Place game objects
 Edit object
properties
 Control level
streaming
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26. Uncharted State Scripts
• State scripts similar in many respects to property-centric model...
 adds finite state machine (FSM) support
 not specifically tied to “properties”
 coarser-grained (one script per object)
• More like scripted extension to existing entity type...
 ... or a “director” that orchestrates actions of other entities
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27. Anatomy of a State Script
• A state script is comprised of:
 attributes
 states
• States define object’s behavior via runtime script code:
 response to events
 natural behavior over time (update event)
 transitional actions between states (begin/end events)
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28. Anatomy of a State Script
State Script 1
Variables
State Script 2
State A
On Update Variables
On Event1
State C
On Begin
State B
On Event4
On Begin
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29. Anatomy of a State Script
State Script 1
Variables Event1
State Script 2
State A
On Update Variables
On Event1
State C
On Begin
State B
On Event4
On Begin
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30. Anatomy of a State Script
State Script 1
Variables Event1
State Script 2
State A
On Update Variables
On Event1
State C
go to
On Begin
State State B
On Event4
On Begin
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31. Anatomy of a State Script
State Script 1
Variables Event1
State Script 2
State A
On Update Variables
On Event1
State C
go to
On Begin
State State B
Event4 On Event4
On Begin
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32. Instantiating a State Script
• Attached to a native (C++) game object: Game
Object
 designers extend or modify native
C++ object type State Script 1
 define entirely new object types
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33. Instantiating a State Script
• Attached to a native (C++) game object: Game
Object
 designers extend or modify native
C++ object type State Script 1
 define entirely new object types
• Attached to a trigger region:
 convex volume Trigger
Region
 detects enter, exit and occupancy
State Script 2
Game Developers Conference 19

34. Instantiating State Scripts
• Placed as stand-alone object:
SsProces
s
 “director” orchestrates actions of
State Script 3
other objects (e.g. IGC)
(stand-alone)
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35. Instantiating State Scripts
• Placed as stand-alone object:
SsProces
s
 “director” orchestrates actions of
State Script 3
other objects (e.g. IGC)
(stand-alone)
• Associated with a task:
Task A
 task = check point
 script manages associated task
Task B1 Task B2
 orchestrates AI encounters
Task C
 controls player objectives
State Script 4
Task D
Game Developers Conference 20

36. Instantiating State Scripts
• Placed as stand-alone object:
SsProces
s
 “director” orchestrates actions of
State Script 3
other objects (e.g. IGC)
(stand-alone)
• Associated with a task:
Task A
 task = check point
 script manages associated task
Task B1 Task B2
 orchestrates AI encounters
Task C
 controls player objectives
State Script 4
• Spawned by another state script
Task D
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37. State Script Syntax
21

38. Game Developers Conference 22

39. State Script Syntax
• State script defined as follows:
 Don’t let Lisp syntax throw you!
 Lisp syntax is all (parentheses)
(define-state-script (quot;kickable-gatequot;)
 Think C/C++ { } blocks (state (quot;lockedquot;)
• Parenthesized blocks highly ...
)
context-sensitive in Lisp/Scheme (state (quot;openingquot;)
...
)
(state (quot;openquot;)
...
)
)
Game Developers Conference 23

40. State Script Syntax
• State script defined as follows:
 Don’t let Lisp syntax throw you!
 Lisp syntax is all (parentheses)
(define-state-script (quot;kickable-gatequot;)
 Think C/C++ { } blocks (state (quot;lockedquot;)
• Parenthesized blocks highly ...
)
context-sensitive in Lisp/Scheme (state (quot;openingquot;)
...
)
(state (quot;openquot;)
...
)
)
Game Developers Conference 23

41. State Script Syntax
• State script defined as follows:
 Don’t let Lisp syntax throw you!
 Lisp syntax is all (parentheses)
(define-state-script (quot;kickable-gatequot;)
 Think C/C++ { } blocks (state (quot;lockedquot;)
• Parenthesized blocks highly ...
)
context-sensitive in Lisp/Scheme (state (quot;openingquot;)
...
)
(state (quot;openquot;)
...
)
)
Game Developers Conference 23

42. State Script Syntax
• State script defined as follows:
 Don’t let Lisp syntax throw you!
 Lisp syntax is all (parentheses)
(define-state-script (quot;kickable-gatequot;)
 Think C/C++ { } blocks (state (quot;lockedquot;)
• Parenthesized blocks highly ...
)
context-sensitive in Lisp/Scheme (state (quot;openingquot;)
...
)
(state (quot;openquot;)
...
)
)
Game Developers Conference 23

43. Event Handler Blocks
(define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
(on (event quot;kickquot;)
... ;; handle quot;kickquot; event
• Each state contains zero or more )
(on (begin)
event handler blocks ... ;; do when state entered
)
(on (update)
... ;; do every frame
)
(on (end)
... ;; do when state exited
)
)
Game Developers Conference 24

44. Event Handler Blocks
(define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
(on (event quot;kickquot;)
... ;; handle quot;kickquot; event
• Each state contains zero or more )
(on (begin)
event handler blocks ... ;; do when state entered
)
(on (update)
... ;; do every frame
)
(on (end)
... ;; do when state exited
)
)
Game Developers Conference 24

45. Event Handler Blocks
(define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
(on (event quot;kickquot;)
... ;; handle quot;kickquot; event
• Each state contains zero or more )
(on (begin)
event handler blocks ... ;; do when state entered
)
(on (update)
... ;; do every frame
)
(on (end)
... ;; do when state exited
)
)
Game Developers Conference 24

46. Event Handler Blocks
(define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
(on (event quot;kickquot;)
... ;; handle quot;kickquot; event
• Each state contains zero or more )
(on (begin)
event handler blocks ... ;; do when state entered
)
(on (update)
... ;; do every frame
)
(on (end)
... ;; do when state exited
)
)
Game Developers Conference 24

47. Event Handler Blocks
(define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
(on (event quot;kickquot;)
... ;; handle quot;kickquot; event
• Each state contains zero or more )
(on (begin)
event handler blocks ... ;; do when state entered
)
(on (update)
... ;; do every frame
)
(on (end)
... ;; do when state exited
)
)
Game Developers Conference 24

48. Runtime Script Code
• Runtime script code inside (on ...) (state (quot;lockedquot;)
(on (begin)
blocks [print-string quot;Starting idle!quot;]
[animate quot;selfquot; quot;locked-idlequot;]
• Simplified Scheme/Lisp )
(on (event quot;kickedquot;)
 Most “commands” are native calls [when [lock-broken?]
into C++ code [print-string quot;BAM!quot;]
]
 Conditional expressions [if [task-complete? quot;wave2quot;]
[print-string quot;Complete!quot;]
 Simple looping via label/goto [print-string quot;NOT!!!quot;]
]
)
)
Game Developers Conference 25

49. Runtime Script Code
• Runtime script code inside (on ...) (state (quot;lockedquot;)
(on (begin)
blocks [print-string quot;Starting idle!quot;]
[animate quot;selfquot; quot;locked-idlequot;]
• Simplified Scheme/Lisp )
(on (event quot;kickedquot;)
 Most “commands” are native calls [when [lock-broken?]
into C++ code [print-string quot;BAM!quot;]
]
 Conditional expressions [if [task-complete? quot;wave2quot;]
[print-string quot;Complete!quot;]
 Simple looping via label/goto [print-string quot;NOT!!!quot;]
]
)
)
Game Developers Conference 25

50. Runtime Script Code
• Runtime script code inside (on ...) (state (quot;lockedquot;)
(on (begin)
blocks [print-string quot;Starting idle!quot;]
[animate quot;selfquot; quot;locked-idlequot;]
• Simplified Scheme/Lisp )
(on (event quot;kickedquot;)
 Most “commands” are native calls [when [lock-broken?]
into C++ code [print-string quot;BAM!quot;]
]
 Conditional expressions [if [task-complete? quot;wave2quot;]
[print-string quot;Complete!quot;]
 Simple looping via label/goto [print-string quot;NOT!!!quot;]
]
)
)
Game Developers Conference 25

51. Runtime Script Code
• Runtime script code inside (on ...) (state (quot;lockedquot;)
(on (begin)
blocks [print-string quot;Starting idle!quot;]
[animate quot;selfquot; quot;locked-idlequot;]
• Simplified Scheme/Lisp )
(on (event quot;kickedquot;)
 Most “commands” are native calls [when [lock-broken?]
into C++ code [print-string quot;BAM!quot;]
]
 Conditional expressions [if [task-complete? quot;wave2quot;]
[print-string quot;Complete!quot;]
 Simple looping via label/goto [print-string quot;NOT!!!quot;]
]
)
)
Game Developers Conference 25

52. User-Defined Functions
(defun verbose-anim ((anim string))
[print-string quot;Starting quot; anim]
[animate quot;selfquot; anim]
)
• Script functions can be defined
and called by script programmer (define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
(on (begin)
[verbose-anim quot;locked-idlequot;]
)
)
...
)
Game Developers Conference 26

53. User-Defined Functions
(defun verbose-anim ((anim string))
[print-string quot;Starting quot; anim]
[animate quot;selfquot; anim]
)
• Script functions can be defined
and called by script programmer (define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
(on (begin)
[verbose-anim quot;locked-idlequot;]
)
)
...
)
Game Developers Conference 26

54. User-Defined Functions
(defun verbose-anim ((anim string))
[print-string quot;Starting quot; anim]
[animate quot;selfquot; anim]
)
• Script functions can be defined
and called by script programmer (define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
(on (begin)
[verbose-anim quot;locked-idlequot;]
)
)
...
)
Game Developers Conference 26

55. User-Defined Functions
(defun verbose-anim ((anim string))
[print-string quot;Starting quot; anim]
[animate quot;selfquot; anim]
)
• Script functions can be defined
and called by script programmer (define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
(on (begin)
[verbose-anim quot;locked-idlequot;]
)
)
...
)
Game Developers Conference 26

56. User-Defined Functions
(defun verbose-anim ((anim string))
[print-string quot;Starting quot; anim]
[animate quot;selfquot; anim]
)
• Script functions can be defined
and called by script programmer (define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
(on (begin)
[verbose-anim quot;locked-idlequot;]
)
)
...
)
Game Developers Conference 26

57. The “Self” Argument
• Any command operating on a game object takes its unique id
(UID) as its first argument
• Magic UID quot;selfquot; refers to the object to which script is attached
gate-17
Game
Object
State Script 1
Game Developers Conference 27

58. The “Self” Argument
• Any command operating on a game object takes its unique id
(UID) as its first argument
• Magic UID quot;selfquot; refers to the object to which script is attached
(on (begin)
gate-17
[animate quot;selfquot; quot;locked-idlequot;]
Game )
Object
State Script 1
self
Game Developers Conference 27

59. The “Self” Argument
• Any command operating on a game object takes its unique id
(UID) as its first argument
• Magic UID quot;selfquot; refers to the object to which script is attached
gate-17 (on (begin)
[animate quot;gate-17quot; quot;locked-idlequot;]
Game
)
Object
State Script 1
Game Developers Conference 27

60. The “Self” Argument
• Any command operating on a game object takes its unique id
(UID) as its first argument
• Magic UID quot;selfquot; refers to the object to which script is attached
gate-17
(on (begin)
Game [animate quot;lock-6quot; quot;fall-offquot;]
Object )
lock-6
State Script 1
Game
Object
Game Developers Conference 27

61. Changing States
(define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
• Transitions to other states via ...
(go quot;state-namequot;) command (on (event quot;kickedquot;)
[when [lock-broken?]
• State transitions cause current [go quot;openingquot;]
]
state’s (on ...) blocks to be )
)
aborted (state (quot;openingquot;)
(on (begin)
• Use (on (exit) ...) block for ...
clean-up )
...
)
)
Game Developers Conference 28

62. Changing States
(define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
• Transitions to other states via ...
(go quot;state-namequot;) command (on (event quot;kickedquot;)
[when [lock-broken?]
• State transitions cause current [go quot;openingquot;]
]
state’s (on ...) blocks to be )
)
aborted (state (quot;openingquot;)
(on (begin)
• Use (on (exit) ...) block for ...
clean-up )
...
)
)
Game Developers Conference 28

63. Changing States
(define-state-script (quot;kickable-gatequot;)
(state (quot;lockedquot;)
• Transitions to other states via ...
(go quot;state-namequot;) command (on (event quot;kickedquot;)
[when [lock-broken?]
• State transitions cause current [go quot;openingquot;]
]
state’s (on ...) blocks to be )
)
aborted (state (quot;openingquot;)
(on (begin)
• Use (on (exit) ...) block for ...
clean-up )
...
)
)
Game Developers Conference 28

64. Tracks
• (on ...) blocks contain one or more tracks
• A track is a bit like a thread or fiber
• Tracks can be put to sleep
 Wait for duration
• e.g., wait 5 seconds,
• wait until frame 23, ...
 Wait for an action to be done
• duration-agnostic
• Tracks can be synchronized via signals
Game Developers Conference 29

65. Tracks
State quot;shake-handsquot;
(state (quot;shake-handsquot;)
(on (begin) On Begin
(track (quot;playerquot;))
Track Track
[wait-move-to quot;playerquot; quot;waypoint7quot;]
P S
[signal quot;player-at-waypointquot;]
[wait-for-signal quot;sully-at-waypointquot;]
[wait-animate quot;playerquot; quot;shake-sullys-handquot;] s-a-w
)
(track (quot;sullivanquot;))
[wait-move-to quot;sullivanquot; quot;waypoint7quot;]
[signal quot;sully-at-waypointquot;] p-a-w
[wait-for-signal quot;player-at-waypointquot;]
[wait-animate quot;sullivanquot; quot;shake-drakes-handquot;]
)
)
)
Game Developers Conference 30

66. Tracks
State quot;shake-handsquot;
(state (quot;shake-handsquot;)
(on (begin) On Begin
(track (quot;playerquot;))
Track Track
[wait-move-to quot;playerquot; quot;waypoint7quot;]
P S
[signal quot;player-at-waypointquot;]
[wait-for-signal quot;sully-at-waypointquot;]
[wait-animate quot;playerquot; quot;shake-sullys-handquot;] s-a-w
)
(track (quot;sullivanquot;))
[wait-move-to quot;sullivanquot; quot;waypoint7quot;]
[signal quot;sully-at-waypointquot;] p-a-w
[wait-for-signal quot;player-at-waypointquot;]
[wait-animate quot;sullivanquot; quot;shake-drakes-handquot;]
)
)
)
Game Developers Conference 30

67. Tracks
State quot;shake-handsquot;
(state (quot;shake-handsquot;)
(on (begin) On Begin
(track (quot;playerquot;))
Track Track
[wait-move-to quot;playerquot; quot;waypoint7quot;]
P S
[signal quot;player-at-waypointquot;]
[wait-for-signal quot;sully-at-waypointquot;]
[wait-animate quot;playerquot; quot;shake-sullys-handquot;] s-a-w
)
(track (quot;sullivanquot;))
[wait-move-to quot;sullivanquot; quot;waypoint7quot;]
[signal quot;sully-at-waypointquot;] p-a-w
[wait-for-signal quot;player-at-waypointquot;]
[wait-animate quot;sullivanquot; quot;shake-drakes-handquot;]
)
)
)
Game Developers Conference 30

68. Tracks
State quot;shake-handsquot;
(state (quot;shake-handsquot;)
(on (begin) On Begin
(track (quot;playerquot;))
Track Track
[wait-move-to quot;playerquot; quot;waypoint7quot;]
P S
[signal quot;player-at-waypointquot;]
[wait-for-signal quot;sully-at-waypointquot;]
[wait-animate quot;playerquot; quot;shake-sullys-handquot;] s-a-w
)
(track (quot;sullivanquot;))
[wait-move-to quot;sullivanquot; quot;waypoint7quot;]
[signal quot;sully-at-waypointquot;] p-a-w
[wait-for-signal quot;player-at-waypointquot;]
[wait-animate quot;sullivanquot; quot;shake-drakes-handquot;]
)
)
)
Game Developers Conference 30

69. Tracks
State quot;shake-handsquot;
(state (quot;shake-handsquot;)
(on (begin) On Begin
(track (quot;playerquot;))
Track Track
[wait-move-to quot;playerquot; quot;waypoint7quot;]
P S
[signal quot;player-at-waypointquot;]
[wait-for-signal quot;sully-at-waypointquot;]
[wait-animate quot;playerquot; quot;shake-sullys-handquot;] p-a-w
)
(track (quot;sullivanquot;))
[wait-move-to quot;sullivanquot; quot;waypoint7quot;]
[signal quot;sully-at-waypointquot;] s-a-w
[wait-for-signal quot;player-at-waypointquot;]
[wait-animate quot;sullivanquot; quot;shake-drakes-handquot;]
)
)
)
Game Developers Conference 30

70. Track Execution Over Time
• Rules for execution of code within a track:
 Greedily consume instructions sequentially...
 ... until a [wait* ...] command encountered...
 ... then relinquish control until the action is complete
• NOTE: A [wait* ...] command doesn’t have to wait; for example:
 [wait-seconds 0]
 [wait-npc-move-to quot;pos-4quot;] when she’s already there
Game Developers Conference 31

71. Options and Variable Declarations
• Options declared at top of
script:
(define-state-script (quot;kickable-gatequot;)
:initial-state quot;closedquot;
 initial state
:declarations (decl-list
 variable declarations
(var quot;num-attemptsquot; :type int32)
(var quot;is-lockedquot; :type boolean :default #t)
 debugging options
)
(state (quot;kickedquot;)
...
)
...
)
Game Developers Conference 32

72. Options and Variable Declarations
• Options declared at top of
script:
(define-state-script (quot;kickable-gatequot;)
:initial-state quot;closedquot;
 initial state
:declarations (decl-list
 variable declarations
(var quot;num-attemptsquot; :type int32)
(var quot;is-lockedquot; :type boolean :default #t)
 debugging options
)
(state (quot;kickedquot;)
...
)
...
)
Game Developers Conference 32

73. Options and Variable Declarations
• Options declared at top of
script:
(define-state-script (quot;kickable-gatequot;)
:initial-state quot;closedquot;
 initial state
:declarations (decl-list
 variable declarations
(var quot;num-attemptsquot; :type int32)
(var quot;is-lockedquot; :type boolean :default #t)
 debugging options
)
(state (quot;kickedquot;)
...
)
...
)
Game Developers Conference 32

74. (define-state-script (quot;kickable-gatequot;)
:initial-state quot;closedquot;
Manipulating Variables :declarations (decl-list
(var quot;num-attemptsquot; :type int32)
• Simple commands for reading (var quot;is-lockedquot; :type boolean :default #t)
)
and writing variables (state (quot;kickedquot;)
(on (begin)
• Lisp/Scheme uses prefix notation [when [get-boolean quot;is-lockedquot;]
[set-int32 quot;num-attemptsquot;
(a.k.a. Polish notation) [+ 1 [get-int32 quot;num-attemptsquot;]]
]
 [+ a b] calculates (a + b) [wait-animate quot;selfquot; quot;kick-failurequot;]
[go quot;closedquot;]
 [set quot;xquot; [+ 1 [get quot;xquot;]]] ]
increments variable “x” ;; else...
[wait-animate quot;selfquot; quot;kick-successquot;]
[go quot;openquot;]
)
)
...
Game Developers Conference 33

75. (define-state-script (quot;kickable-gatequot;)
:initial-state quot;closedquot;
Manipulating Variables :declarations (decl-list
(var quot;num-attemptsquot; :type int32)
• Simple commands for reading (var quot;is-lockedquot; :type boolean :default #t)
)
and writing variables (state (quot;kickedquot;)
(on (begin)
• Lisp/Scheme uses prefix notation [when [get-boolean quot;is-lockedquot;]
[set-int32 quot;num-attemptsquot;
(a.k.a. Polish notation) [+ 1 [get-int32 quot;num-attemptsquot;]]
]
 [+ a b] calculates (a + b) [wait-animate quot;selfquot; quot;kick-failurequot;]
[go quot;closedquot;]
 [set quot;xquot; [+ 1 [get quot;xquot;]]] ]
increments variable “x” ;; else...
[wait-animate quot;selfquot; quot;kick-successquot;]
[go quot;openquot;]
)
)
...
Game Developers Conference 33

76. (define-state-script (quot;kickable-gatequot;)
:initial-state quot;closedquot;
Manipulating Variables :declarations (decl-list
(var quot;num-attemptsquot; :type int32)
• Simple commands for reading (var quot;is-lockedquot; :type boolean :default #t)
)
and writing variables (state (quot;kickedquot;)
(on (begin)
• Lisp/Scheme uses prefix notation [when [get-boolean quot;is-lockedquot;]
[set-int32 quot;num-attemptsquot;
(a.k.a. Polish notation) [+ 1 [get-int32 quot;num-attemptsquot;]]
]
 [+ a b] calculates (a + b) [wait-animate quot;selfquot; quot;kick-failurequot;]
[go quot;closedquot;]
 [set quot;xquot; [+ 1 [get quot;xquot;]]] ]
increments variable “x” ;; else...
[wait-animate quot;selfquot; quot;kick-successquot;]
[go quot;openquot;]
)
)
...
Game Developers Conference 33

77. (define-state-script (quot;kickable-gatequot;)
:initial-state quot;closedquot;
Manipulating Variables :declarations (decl-list
(var quot;num-attemptsquot; :type int32)
• Simple commands for reading (var quot;is-lockedquot; :type boolean :default #t)
)
and writing variables (state (quot;kickedquot;)
(on (begin)
• Lisp/Scheme uses prefix notation [when [get-boolean quot;is-lockedquot;]
[set-int32 quot;num-attemptsquot;
(a.k.a. Polish notation) [+ 1 [get-int32 quot;num-attemptsquot;]]
˘
]
 [+ a b] calculates (a + b) [wait-animate quot;selfquot; quot;kick-failurequot;]
[go quot;closedquot;]
 [set quot;xquot; [+ 1 [get quot;xquot;]]] ]
increments variable “x” ;; else...
[wait-animate quot;selfquot; quot;kick-successquot;]
[go quot;openquot;]
)
)
...
Game Developers Conference 33

78. (define-state-script (quot;kickable-gatequot;)
:initial-state quot;closedquot;
Manipulating Variables :declarations (decl-list
(var quot;num-attemptsquot; :type int32)
• Simple commands for reading (var quot;is-lockedquot; :type boolean :default #t)
)
and writing variables (state (quot;kickedquot;)
(on (begin)
• Lisp/Scheme uses prefix notation [when [get-boolean quot;is-lockedquot;]
[set-int32 quot;num-attemptsquot;
(a.k.a. Polish notation) [+ 1 [get-int32 quot;num-attemptsquot;]]
]
 [+ a b] calculates (a + b) [wait-animate quot;selfquot; quot;kick-failurequot;]
[go quot;closedquot;]
 [set quot;xquot; [+ 1 [get quot;xquot;]]] ]
increments variable “x” ;; else...
[wait-animate quot;selfquot; quot;kick-successquot;]
[go quot;openquot;]
)
)
...
Game Developers Conference 33

79. Configuration Parameters
• All game objects have
properties (key-value pairs)
 Property values edited in
Charter
Game Developers Conference 34

80. Configuration Parameters
• All game objects have
properties (key-value pairs)
 Property values edited in
Charter
Game Developers Conference 34

81. Configuration Parameters
• Designers can create their
own free-form properties,
called tags meaning-of-life = 42
 Simply type “key = value”
in Tags field
Game Developers Conference 34

82. Configuration Parameters
• State scripts have read-only access to game object properties...
 ... and free-form tags
Game Developers Conference 35

83. Configuration Parameters
• State scripts have read-only access to game object properties...
 ... and free-form tags
(define-state-script (quot;kickable-gatequot;)
(state (quot;kickedquot;)
(on (begin)
[wait-animate quot;selfquot;
[tag-string quot;kick-animquot;]
]
)
...
)
Game Developers Conference 35

84. Configuration Parameters
• State scripts have read-only access to game object properties...
 ... and free-form tags
(define-state-script (quot;kickable-gatequot;)
(state (quot;kickedquot;)
(on (begin)
[wait-animate quot;selfquot;
[tag-string quot;kick-animquot;]
]
)
...
)
Game Developers Conference 35

85. Configuration Parameters
• State scripts have read-only access to game object properties...
 ... and free-form tags
(define-state-script (quot;kickable-gatequot;)
(state (quot;kickedquot;)
(on (begin)
[wait-animate quot;selfquot;
[tag-string quot;kick-animquot;]
]
)
...
)
Game Developers Conference 35

86. Data Definition and Runtime
(define-state-script (quot;kickable-gatequot;)
• Offline data-definition language (state (quot;lockedquot;)
(on (begin)
(Scheme) is intermingled with [print-string quot;Starting idle!quot;]
[animate quot;selfquot; quot;locked-idlequot;]
runtime code )
(on (event quot;kickedquot;)
[when [lock-broken?]
[print-string quot;BAM!quot;]
]
[if [task-complete? quot;wave2quot;]
[print-string quot;Complete!quot;]
[print-string quot;NOT!!!quot;]
]
)
)
...
)
Game Developers Conference 36

87. Data Definition and Runtime
(define-state-script (quot;kickable-gatequot;)
• Offline data-definition language (state (quot;lockedquot;)
(on (begin)
(Scheme) is intermingled with [print-string quot;Starting idle!quot;]
[animate quot;selfquot; quot;locked-idlequot;]
runtime code )
(on (event quot;kickedquot;)
[when [lock-broken?]
[print-string quot;BAM!quot;]
]
[if [task-complete? quot;wave2quot;]
[print-string quot;Complete!quot;]
[print-string quot;NOT!!!quot;]
]
)
)
...
)
Game Developers Conference 36

88. Data Definition and Runtime
class Vector3
{
private:
float x, y, z;
• Really no different than the public:
float Dot(const Vector3& b)
distinction between declarations {
return (x * b.x
and definitions in C++ + y * b.y
+ z * b.z);
}
...
};
Game Developers Conference 36

89. Data Definition and Runtime
class Vector3
{
private:
float x, y, z;
• Really no different than the public:
float Dot(const Vector3& b)
distinction between declarations {
return (x * b.x
and definitions in C++ + y * b.y
+ z * b.z);
}
...
};
Game Developers Conference 36

90. Case Studies
37

91. Custom Object Type: Breakable Sign
Game Developers Conference 38

92. Custom Object Type: Breakable Sign
Game Developers Conference 38

93. Custom Object Type: Breakable Sign
(define-state-script (quot;falling-signquot;)
(state (quot;untouchedquot;)
(on (update)
[when [task-complete? quot;wz-post-combatquot;]
[go quot;fallenquot;]
]
)
(on (event quot;hanging-fromquot;)
[go quot;breakingquot;]
)
)
...
Game Developers Conference 39

94. Custom Object Type: Breakable Sign
(define-state-script (quot;falling-signquot;)
(state (quot;untouchedquot;)
(on (update)
[when [task-complete? quot;wz-post-combatquot;]
[go quot;fallenquot;]
]
)
(on (event quot;hanging-fromquot;)
[go quot;breakingquot;]
)
)
...
Game Developers Conference 39

95. Custom Object Type: Breakable Sign
(define-state-script (quot;falling-signquot;)
(state (quot;untouchedquot;)
(on (update)
[when [task-complete? quot;wz-post-combatquot;]
[go quot;fallenquot;]
]
)
(on (event quot;hanging-fromquot;)
[go quot;breakingquot;]
)
)
...
Game Developers Conference 39

96. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
quot;hingequot;
quot;sign-break-dustquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
)
)
(state (quot;fallenquot;)
(on (begin)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
)
Game Developers Conference 39

97. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
quot;hingequot;
quot;sign-break-dustquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
)
)
(state (quot;fallenquot;)
(on (begin)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
)
Game Developers Conference 39

98. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
quot;hingequot;
quot;sign-break-dustquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
)
)
(state (quot;fallenquot;)
(on (begin)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
)
Game Developers Conference 39

99. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
quot;hingequot;
quot;sign-break-dustquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
)
)
(state (quot;fallenquot;)
(on (begin)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
)
Game Developers Conference 39

100. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
quot;hingequot;
quot;sign-break-dustquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
)
)
(state (quot;fallenquot;)
(on (begin)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
)
Game Developers Conference 39

101. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
quot;hingequot;
quot;sign-break-dustquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
)
)
(state (quot;fallenquot;)
(on (begin)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
)
Game Developers Conference 39

102. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
quot;hingequot;
quot;sign-break-dustquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
)
)
(state (quot;fallenquot;)
(on (begin)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
)
Game Developers Conference 39

103. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
quot;hingequot;
quot;sign-break-dustquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
)
)
(state (quot;fallenquot;)
(on (begin)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
)
Game Developers Conference 39

104. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
quot;hingequot;
quot;sign-break-dustquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
)
)
(state (quot;fallenquot;)
(on (begin)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
)
Game Developers Conference 39

105. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
(define-state-script (quot;falling-signquot;)
[spawn-particles-at-joint quot;selfquot;
(state (quot;untouchedquot;)
quot;hingequot;
(on (update)
quot;sign-break-dustquot;]
[when [task-complete? quot;wz-post-combatquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
[go quot;fallenquot;]
]
)
)
)
(on (event quot;hanging-fromquot;)
(state (quot;fallenquot;)
[go quot;breakingquot;]
(on (begin)
)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
...
)
)
Game Developers Conference 39

106. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
(define-state-script (quot;falling-signquot;)
[spawn-particles-at-joint quot;selfquot;
(state (quot;untouchedquot;)
quot;hingequot;
(on (update)
quot;sign-break-dustquot;]
[when [task-complete? quot;wz-post-combatquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
[go quot;fallenquot;]
]
)
)
)
(on (event quot;hanging-fromquot;)
(state (quot;fallenquot;)
[go quot;breakingquot;]
(on (begin)
)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
...
)
)
Game Developers Conference 39

107. Custom Object Type: Breakable Sign
(state (quot;breakingquot;)
(on (begin)
(define-state-script (quot;falling-signquot;)
[spawn-particles-at-joint quot;selfquot;
(state (quot;untouchedquot;)
quot;hingequot;
(on (update)
quot;sign-break-dustquot;]
[when [task-complete? quot;wz-post-combatquot;]
[wait-animate quot;selfquot; quot;sign-breakquot;]
[go quot;fallenquot;]
[go quot;fallenquot;]
]
)
)
)
(on (event quot;hanging-fromquot;)
(state (quot;fallenquot;)
[go quot;breakingquot;]
(on (begin)
)
[animate quot;selfquot; quot;sign-brokenquot;] ;; looping
)
)
...
)
)
Game Developers Conference 39

108. Making the Sign Script Generic
(state (quot;animatingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
(define-state-script (quot;simple-animating-objquot;)
[tag-string quot;particle-jointquot;]
(state (quot;initialquot;)
[tag-string quot;particle-namequot;]]
(on (update)
[wait-animate quot;selfquot;
[when [task-complete?
[tag-string quot;anim-namequot;]]
[tag-string quot;done-taskquot;]]
[go quot;donequot;]
[go quot;donequot;]
)
]
)
)
(state (quot;donequot;)
(on (event quot;hanging-fromquot;)
(on (begin)
[go quot;animatingquot;]
[animate quot;selfquot;
)
[tag-string quot;done-anim-namequot;]]
)
)
...
)
)
Game Developers Conference 40

109. Making the Sign Script Generic
(state (quot;animatingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
(define-state-script (quot;simple-animating-objquot;)
[tag-string quot;particle-jointquot;]
(state (quot;initialquot;)
[tag-string quot;particle-namequot;]]
(on (update)
[wait-animate quot;selfquot;
[when [task-complete?
[tag-string quot;anim-namequot;]]
[tag-string quot;done-taskquot;]]
[go quot;donequot;]
[go quot;donequot;]
)
]
)
)
(state (quot;donequot;)
(on (event quot;hanging-fromquot;)
(on (begin)
[go quot;animatingquot;]
[animate quot;selfquot;
)
[tag-string quot;done-anim-namequot;]]
)
)
...
)
)
Game Developers Conference 40

110. Making the Sign Script Generic
(state (quot;animatingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
(define-state-script (quot;simple-animating-objquot;)
[tag-string quot;particle-jointquot;]
(state (quot;initialquot;)
[tag-string quot;particle-namequot;]]
(on (update)
[wait-animate quot;selfquot;
[when [task-complete?
[tag-string quot;anim-namequot;]]
[tag-string quot;done-taskquot;]]
[go quot;donequot;]
[go quot;donequot;]
)
]
)
)
(state (quot;donequot;)
(on (event quot;hanging-fromquot;)
(on (begin)
[go quot;animatingquot;]
[animate quot;selfquot;
)
[tag-string quot;done-anim-namequot;]]
)
)
...
)
)
Game Developers Conference 40

111. Making the Sign Script Generic
(state (quot;animatingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
(define-state-script (quot;simple-animating-objquot;)
[tag-string quot;particle-jointquot;]
(state (quot;initialquot;)
[tag-string quot;particle-namequot;]]
(on (update)
[wait-animate quot;selfquot;
[when [task-complete?
[tag-string quot;anim-namequot;]]
[tag-string quot;done-taskquot;]]
[go quot;donequot;]
[go quot;donequot;]
)
]
)
)
(state (quot;donequot;)
(on (event quot;hanging-fromquot;)
(on (begin)
[go quot;animatingquot;]
[animate quot;selfquot;
)
[tag-string quot;done-anim-namequot;]]
)
)
...
)
)
Game Developers Conference 40

112. Making the Sign Script Generic
(state (quot;animatingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
(define-state-script (quot;simple-animating-objquot;)
[tag-string quot;particle-jointquot;]
(state (quot;initialquot;)
[tag-string quot;particle-namequot;]]
(on (update)
[wait-animate quot;selfquot;
[when [task-complete?
[tag-string quot;anim-namequot;]]
[tag-string quot;done-taskquot;]]
[go quot;donequot;]
[go quot;donequot;]
)
]
)
)
(state (quot;donequot;)
(on (event quot;hanging-fromquot;)
(on (begin)
[go quot;animatingquot;]
[animate quot;selfquot;
)
[tag-string quot;done-anim-namequot;]]
)
)
...
)
)
Game Developers Conference 40

113. Making the Sign Script Generic
(state (quot;animatingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
(define-state-script (quot;simple-animating-objquot;)
[tag-string quot;particle-jointquot;]
(state (quot;initialquot;)
[tag-string quot;particle-namequot;]]
(on (update)
[wait-animate quot;selfquot;
[when [task-complete?
[tag-string quot;anim-namequot;]]
[tag-string quot;done-taskquot;]]
[go quot;donequot;]
[go quot;donequot;]
)
]
)
)
(state (quot;donequot;)
(on (event quot;hanging-fromquot;)
(on (begin)
[go quot;animatingquot;]
[animate quot;selfquot;
)
[tag-string quot;done-anim-namequot;]]
)
)
...
)
)
Game Developers Conference 40

114. Making the Sign Script Generic
(state (quot;animatingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
(define-state-script (quot;simple-animating-objquot;)
[tag-string quot;particle-jointquot;]
(state (quot;initialquot;)
[tag-string quot;particle-namequot;]]
(on (update)
[wait-animate quot;selfquot;
[when [task-complete?
[tag-string quot;anim-namequot;]]
[tag-string quot;done-taskquot;]]
[go quot;donequot;]
[go quot;donequot;]
)
]
)
)
(state (quot;donequot;)
(on (event quot;hanging-fromquot;)
(on (begin)
[go quot;animatingquot;]
[animate quot;selfquot;
)
[tag-string quot;done-anim-namequot;]]
)
)
...
)
)
Game Developers Conference 40

115. Making the Sign Script Generic
(state (quot;animatingquot;)
(on (begin)
[spawn-particles-at-joint quot;selfquot;
(define-state-script (quot;simple-animating-objquot;)
[tag-string quot;particle-jointquot;]
(state (quot;initialquot;)
[tag-string quot;particle-namequot;]]
(on (update)
[wait-animate quot;selfquot;
[when [task-complete?
[tag-string quot;anim-namequot;]]
[tag-string quot;done-taskquot;]]
[go quot;donequot;]
[go quot;donequot;]
)
]
)
)
(state (quot;donequot;)
(on (event quot;hanging-fromquot;)
(on (begin)
[go quot;animatingquot;]
[animate quot;selfquot;
)
[tag-string quot;done-anim-namequot;]]
)
)
...
)
)
Game Developers Conference 40