Mid-Semester Feedback

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2 Mid-Semester Feedback We re happy that you re happy Top complaint: I feel behind Retry system has you covered and we did warn you about the snowball Overall Happiness (1-5)

3 Mid-Semester Grades Your current grade reports have been sent or ask at hours with questions/problems Keep up the good work

4 Special Topics Lectures Covering engine features from final projects and midsemester feedback Keep your eyes out for an survey this week

5 Announcements QUESTIONS?

6 Zynga Guest Lecture Kate Bambino, Senior Product Manager

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8 Content Management II GAME LOGIC MANAGEMENT

9 Why are we doing this again? Prevent excecutable bloat Quickly make asset changes Some content is already separated Graphics are out Maps are out Recap

10 What is Game Logic? Game logic dictates the rules of your game Consider a chess game Maps set up a chess problem Images define how the game looks but game logic controls how the pieces move You probably hard code this

11 Why not hard code logic? Programmers aren t game designers And they shouldn t be game designers personal assistants either Game logic should be reusable Imagine multiple games in a series Convenience it s faster

12 Content Management II SOME POSSIBLE SOLUTIONS

13 Put Logic in Config Files Logic is defined in external files, sort of like Tac maps Good for static information Unit stats, like how much health tanks start with Game settings, like screen size or default level Trickier when trying to define interactions How would you define the M2 grenade?

14 Embed a Scripting Language Logic is defined by a scripting language, then loaded at runtime Good for complicated behavior Wouldn t Tac AI have been so much easier? Lots of overhead Need a well-designed API Designers have to learn API

15 Make a Game-specific Editor Logic is defined in a settings application tailormade for the game Very easy to use Engines can even be aimed at non-programmers (RPGmaker etc) Inherently not portable And you have to spend all that time writing it again!

16 What Features do we Need? Shouldn t be tied to any specific game genre Because our engine isn t either Need to define entity interactions For instance, how would we make a weighted button?

17 Content Management II QUESTIONS?

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19 Entity I/O WHAT S ENTITY I/O?

20 Introducing Entity I/O Strategy for logically connecting entities Connections are defined by designers and dictate game logic Popularized in the Source engine When button is depressed, release rock

21 Inputs and Outputs Entities have outputs button.onpress() timer.onfinish() camera.onseen() Entities have inputs door.doopen() bomb.doexplode() lights.dotoggle() doopen() onpush()

22 Some Example Uses Light switch switch.onflip() light.dotoggle() Puzzles ocarina.onplay() timecube.doraise() Automatic door camera.onplayerseen() door.doopen()

23 Connecting Entities An output can be connected to an input to define a behavior An output is connected to any number of inputs This might seem backwards, but think of connecting wires Programmer defines inputs/outputs Designers connect inputs/outputs onpush() -> doopen()

24 Invisible Logic Entities? Entities need not be physical What about an invisible hitbox that performs some logic when the player enters the box? and a Timer doesn t physically interact at all!

25 Special Logic Entity: Sensor Sends a signal when some other entity touches it Not necessarily physical Triggers when a player enters an area, etc Can you think of some uses?

26 Special Logic Entity: Relay Think of it as a pipe with a valve Relays a signal from one entity to another but only when it s received some other signal doenable()/dodisable() dofire() onfire() Relay

27 Entity I/O IMPLEMENTING ENTITY I/O

28 Engine Objects An Output, to send a pulse to all attached inputs An Input, to hold and run arbitrary game code Potentially a Connection to go between them Allows passing connection properties as input arguments Output Connection Input Pulse Arguments

29 Setting Up Connections Connections are defined outside the game code These are loaded from data Data needs to be turned into your Output and Input objects Then these objects fire at their appropriate times in game Data file World Inititalization Output objects and Input objects Key/value pairs Connection objects

30 Some Sample Contracts public class Output { private List<Connection> connections; public void connect(connection c) { connections.add(c) } public void run() { for (Connection c : connections) c.run() } } public class Connection { private Input target; private Map<String, String> args; public void run() { target.run(args); } } abstract public class Input { public abstract void run(map<string, String> args); }

31 Game Code Need to read connections from data files and then initialize them Entity subclasses can have outputs/inputs But there might be some common ones: oncollide etc Inputs need game-specific logic public class Door extends Entity { } private Output ondooropen; public OpenDoorInput doopendoor; private void opendoor() { } // door open code ondooropen.run(); class OpenDoorInput extends Input { public void run() { opendoor(); } }

32 Content Management II QUESTIONS?

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34 Reflection and Friends Avoid Class.forName() What happens when code is refactored? Have to sync data and code Instead, map from strings to classes Map<String, Class<?>> (Also, cs195n publisher obfuscates demos, breaking most reflection)

35 Connections, not Logic Gates Connections send discrete events, not electrical signals These events occur at some exact point in time; they don t become true Can t be evaluated like state machine transitions So they require a different structure

36 Tips for M3 JAVA TIP OF THE WEEK

37 Functions aren t objects In some languages, functions are first class objects In Java this is not the case So functions (and arbitrary code) can t be stored so easily void map(list list, Function lambda) { for (Object o : list) { lambda(o); } } // in your connection code map(connections, Connection.run);

38 Introducing Anonymous Classes Essentially an in-line subclass Looks exactly like a subclass in another file, minus the name All anonymous classes are inner classes And therefore have a reference to their superclass interface Mappable { abstract void run(object o); } void map(list list, Mappable lambda) { for (Object o : list) { lambda.run(o); } } map(mylist, new Mappable() { void run(object o) { docoolstuff(o); } });

39 Use: Adapter Classes Adapters pass some code or function to another object Hey, this sounds a lot like an Input Subclass them in-line to avoid having to write new classes each time public class Door extends Entity { private Output onopen; public Input doopen = new Input() { public void run() { opendoor(); } }; } private void opendoor() { // door open code onopen.run(); }

40 Use: Listener Classes Listeners wait for events from other objects Subclass them in-line to avoid writing new designated listeners A lot more elegant than having a logic class implement ten interfaces! // inside, say, a JPanel somewhere addactionlistener(new ActionListener(){ actionperformed(actionevent e) { // handle the action as normal } }

41 Some Restrictions No way to use extends or implements No non-final static fields No constructors Instance initializers exist for exactly this reason!

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43 Presentation Order 1. wyegelwe 2. cody 3. kkutt 4. jslu 5. ebirenba 6. aabouche 7. sswarr 8. kloh 9. istrickm 10. lelberty 11. jhertz 12. jte 13. gtrousda 14. gamyers 15. jqtran

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