Game Development Methodologies and Programming Languages

1. CSCE 552 Fall 2012 Language and Programming By Jijun Tang

2. Design Procedure • Waterfall method • Development methodology • Design and production are broken into phases • Iterative development • Practice of producing things incrementally • Refining and re-refining the product • May iterate many cycles before get it right

3. Waterfall vs. Iterative testing

4. Programming Teams • In the 1980s programmers developed the whole game (and did the art and sounds too!) • Now programmers write code to support designers and artists (content creators)

5. Different Programs • Game code Anything related directly to the game • Game engine Any code that can be reused between different games • Tools In house tools Plug-ins for off-the-shelf tools

6. Methodologies: Code and Fix • Unfortunately very common • Little or no planning • Always reacting to events • Poor quality and unreliability of finished product • “Crunch” time normal

7. Methodologies: Waterfall • Very well-defined steps in development • Lots of planning ahead of time • Great for creating a detailed milestone schedule • Doesn't react well to changes • Game development is too unpredictable for this approach

8. Methodologies: Iterative • Multiple development cycles during a single project • Each delivering a new set of functionality • Refinements are needed • The game could ship at any moment • Allows for planning but also for changes

9. Methodologies: Agile Methods • Deal with the unexpected • Very short iterations: 2-3 weeks • Iterate based on feedback of what was learned so far • Very good visibility of state of game • Difficult for publishers or even developers to adopt because it's relatively new

10. Leveraging Existing Code • A lot of code that games use is the same • It's a total waste of time to write it over and over • Instead, spend your time in what's going to make your game unique • Avoid Not Invented Here (NIH) syndrome!

11. Where Are Existing Codes • Reuse code from previous project • Easier in a large company if you have an engine and tools group • Use freeware code and tools • No support • Make sure license allows it • Middleware • Companies provide with components used in game development • physics, animation, graphics, etc • Commercial game engines • You can license the whole engine and tools and a single package • Good if you're doing exactly that type of game

12. Languages • C/C++ • Java • Script: Flash, Python, LISP, etc. • C# • XNA for PC and Xbox

13. C++ • C/C++ used to be the most popular language for games • Today, C++ is still the language of choice for game development (according to wiki)

14. C++: Strengths - I • Performance • Control over low-level functionality (memory management, etc) • Can switch to assembly or C whenever necessary • Good interface with OS, hardware, and other languages • High-level, object-oriented • High-level language features are essential for making today's complex games • Has inheritance, polymorphism, templates, and exceptions • Strongly typed, so it has improved reliability

15. C++: Strengths - II • C Heritage • C++ is the only high-level language that is backwards-compatible with C • Has APIs and compiler support in all platforms • Easier transition for experienced programmers • Libraries • STL (Standard Template Library) • Comprehensive set of standard libraries • Boost: widely used library with wide variety of functionality • Many commercial C++ libraries also available

16. C++: Weaknesses - I • Too low-level • Still forces programmers to deal with low-level issues • Too error-prone • Attention to low-level details is overkill for high-level features or tools • Slow iteration • C++ is fully compiled into binary format from source code • Compiling large numbers of files is very slow • This will only become more of a problem as games become more complex

17. C++: Weaknesses - II • Too complicated • Because of its C heritage, C++ is very complicated • Long learning curve to become competent with the language • Lacking features • No reflection or introspection features • No method of object serialization • No native support for message passing

18. C++: When to Use It? • When performance is crucial • If your current code base is mostly C and C++ • If you have a lot of in-house expertise in C++ • Avoid using it for high-level code, such as tools

19. Java for Game Development • Why use Java? • It's a high-level OO language that simplifies many C++ features • Adds several useful high-level features • Easy to develop for multiple platforms because of intermediate bytecode • Good library support

20. Java Performance • Has typically been Java's weak point • Has improved in the last few years: still not up to C++ level, but very close • Uses Just-In-Time compiling and HotSpot optimizations • Now has high-performance libraries • Also has access to native functionality

21. Java Platforms • Well suited to downloadable and browser-based games • Dominates development on mobile and handheld platforms • Possible to use in full PC games, but more likely to be embedded into a game

22. Commercial Games using Java • Downloadable games like those from PopCap Games: Mummy Maze, etc • Online card games • PC games using Java as a scripting language: Vampire: The Masquerade, Star Wars Galaxies • PC games fully written in Java: You Don't Know Jack, Who Wants to Be a Millionaire

23. C# • Developed by MS, now ISO standard • A simple, modern, general-purpose, object-oriented programming language • Support for software engineering principles: • strong type checking • array bounds checking • detection of attempts to use uninitialized variables • automatic garbage collection. • Software robustness, durability, and programmer productivity are important.

24. Strength and Weakness • C# is intended to be suitable for writing applications for both hosted and embedded systems • Source code portability is very important, as is programmer portability • Although is intended to be economical (memory/processing power), it cannot compete directly with C or assembly language.

25. Scripting Languages • Why use scripting languages? • Ease and speed of development • Short iteration time • Code becomes a game asset • Offer additional features and are customizable

26. Drawbacks of Scripting Languages • Slow performance • Limited tool support • Dynamic typing makes it difficult to catch errors • Awkward interface with the rest of the game • Difficult to implement well

27. Popular scripting languages • Python • Lua • Other off-the-shelf options such as Ruby, Perl, Javascript • Custom scripting languages • UnrealScript, QuakeC, NWNScript

28. Lua Example

29. Choose a Scripting Languages • Consider whether you need one at all • What features do you need? • What kind of performance do you need? • What debugging facilities does the language have? • On what platforms does it need to run? • What resources and expertise are available?

30. Programming Fundamentals

31. Data Structures: Array • Elements are adjacent in memory (great cache consistency) • Requires continuous memory space • They never grow or get reallocated • Use dynamic incremental array concept • GCC has a remalloc function • In C++ there's no check for going out of bounds • Use vector if possible • Keep in mind of checking boundaries • Inserting and deleting elements in the middle is expensive

32. List • Very cheap to add/remove elements. • Available in the STL (std::list) • Every element is allocated separately, not placed contiguously in memory • Lots of little allocations • Bad cache awareness, but can use arrays to hold pre-allocated items • Single/Double linked list

33. Lists

34. Dictionaries • Maps a set of keys to some data. • std::map, std::hash, etc • Very fast access to data • Perfect for mapping IDs to pointers, or resource handles to objects • May waste space, need to design comparison operators

35. Hash Table

36. Others • Stacks • First in, last out • std::stack adaptor in STL • Queues • First in, first out • std::deque • Priority queue is useful in game to schedule events

37. Stack/Queue/Priority Queue

38. Bit packing • Fold all necessary data into a smaller number of bits • Bool in C++ may use up to 4 bytes, thus is very expensive • Very useful for storing boolean flags: pack 32 in an integer • Possible to apply to numerical values if we can give up range or accuracy • Very low level trick • Use shifts to handle the operation or use assembly • Only use when absolutely necessary

39. Bits

40. Inheritance • Models “is-a” relationship • Extends behavior of existing classes by making minor changes • Do not overuse, if possible, use component systerm • UML diagram representing inheritance

41. Polymorphism • The ability to refer to an object through a reference (or pointer) of the type of a parent class • Key concept of object oriented design • C++ implements it using virtual functions

42. Multiple Inheritance • Allows a class to have more than one base class • Derived class adopts characteristics of all parent classes • Huge potential for problems (clashes, casting, dreaded diamond, etc) • Multiple inheritance of abstract interfaces is much less error prone (virtual inheritance) • Java has no multiple inheritance

43. Dreaded Diamond • It is an ambiguity that arises when two classes B and C inherit from A, and class D inherits from both B and C. • If a method in D calls a method defined in A (and does not override the method), and B and C have overridden that method differently, then from which class does it inherit: B, or C?

44. Component Systems • Component system organization

45. Object Factory • Creates objects by name • Pluggable factory allows for new object types to be registered at runtime • Extremely useful in game development for passing messages, creating new objects, loading games, or instantiating new content after game ships

46. Factory Pattern

47. Simple Sample Factory - I

48. Simple Sample Factory - II

49. Singleton • Implements a single instance of a class with global point of creation and access • For example, GUI • Don't overuse it!!!

50. Singleton Example