WIXLIB

3D Racing Car Game2009-05-19tions about what sort of project couldbenefit from implementing a particularmodel. With this in regard, one canconclude that a process paradigmprovides a framework that may beadapted to form a process which suits aparticular project.There are three major process paradigms that are commonly used today insoftware engineering practice; thewaterfall model, component-basedsoftware engineering and evolutionarydevelopment2.The Waterfall ModelThe waterfall model is recommendedfor large and complex systems thathave a long life-time 2. Some systemswhich carry these attributes are alsocritical systems. This means that if afault would occur, it may result in:Threat to human life (death orinjury)Economic lossEnvironmental damage2It is believed that the waterfall modelwould be an appropriate choice whendeveloping a critical system, since themodel emphasises on thoroughness3.The basic concept is to take all theactivities and treat them separately.One activity is always followed byanother, in the same way water travelsdown some falls. This descriptionbecomes even more obvious whenlooking at a visualization of the model(Figure 2).RequirementsdefinitionSystem andsoftware designImplementationand unit testingIntegration andsystem testingOperation andmaintenanceFigure 2: The waterfall model2.1. Requirements definition Allrequirements on the system arefound by talking to system users.Example of requirements can beservices, constraints and goals,such as “We want a webpage thatcolour-blind people can enjoy”.2. System and software design Inthis activity, the overallarchitecture of the system isestablished.3. Implementation and unit testingThe software is implemented inunits which also are tested.4. Integration and system testingThe units are merged togetherinto a complete system. Furthertesting is required.5. Operation and maintenance Thesystem is delivered to thecustomer and put into operation.“Bugs” are almost always found,and therefore the systemrequired bug-fixing andmaintenance.In each of the activities describedabove, one or several documents areproduced. The idea is not to start on anew activity until the documentsbelonging to the previous activity issigned off, but in practice, this is nothow it is done. Instead most of theactivitiesoverlapandallthedocuments feed information to thedifferent activities. Although thesedocuments provide a good overlook,10 (51)

3D Racing Car Game2009-05-19they are very costly to produce. Due tothe cost of constantly producing, signing and reworking documents, thewaterfall model should not be appliedto a project where one is uncertainabout the requirements 2.Evolutionary DevelopmentThis model is recommended for smalland medium-sized systems that shallbe developed rapidly2. The idea is thatspecification, implementation andvalidation should work as concurrentthreads, all supplying input to theother activities. Customer input isconsidered to be very important, if noteven necessary for the developmentand outcome of the project.Component-based SoftwareEngineeringAs the name suggest, this model is usedwhen there are several already existingcomponents which can be reused andput together to form a system.Normally, reuse is an important part ofany software process, but in this case itis the fundamental activity. The firstand the last activities, requirementsspecification and system validation, arethe same as in any process model, butthe intermediate activities differ fromother models.At the beginning of a project, an initialimplementation of the software isproduced and released to the customer.This way, the customer can makeimprovements and further describedetails, which might not have beenclear to the developers. Gradually thesystem will improve, and when thefinal release comes, the customershould be fully satisfied with thesystem.During the component analysis, onesearchesforcomponentsthatcorrespond to the requirements. Whenthe right components are found, theymight differ a bit from the originalrequirement specification, thus leadingto a modification of the requirements.Before the system is developed and thecomponents are integrated, thearchitecture of the system must beestablished.Thisisdoneinconsideration to the found components. When all of the componentsare fully integrated, it is time nalysisRequirementsmodificationDevelopmentand utionary development is dividedinto two major types:1. Exploratory development Thedevelopment start with therequirements that are bestunderstood. To further evolve thesystem, new features areproposed by the customer. Thisidea relies on the customer’swillingness to spend much timecontributing to the project.2. Throwaway prototyping Thedevelopment starts with therequirements that are poorlyunderstood, because there is noneed to prototype requirementsthat you already understand.System designwith reuseSystemvalidationsoftware11 (51)2.2.1. Our Development ProcessIn this project, evolutionary development was chosen as a keystone for our

3D Racing Car Game2009-05-19development process. The decision wasmainly based on the size and theduration of the project. We had alimited amount of time, namely 4.5months, and during this time ngineering was easily dismissed sincethere were very few, or none,components to work with. Thewaterfall model was dismissed, since itfocuses a lot on writing documents,which is a very time-consumingactivity.these two models are connected toevolutionary development, and whichlevel of detail they hold, is representedby Figure 4.When it came to deciding whether togo with throwaway prototyping orexploratory development, the latterwas chosen. This decision was based onthe following facts. The greatestproblem was not to understand thebasic requirements, but how muchtime it would take implementing themany possible features. Given thecircumstances, the best strategy wasfirsttoimplementthegamefoundation, and subsequently implement one feature after another, henceusing exploratory development.For example, agile methods agree withevolutionary development on somepoints, but other ideas and conceptsmay be added, hence the agile circle isnot totally encased by the evolutionarycircle. The heights of the circlesindicate what level of detail the modelshold. XP is more detailed than agile,whichismoredetailedthanevolutionary.Figure 4: Visual description of how differentprocess models are related to each other.Since we, in this project, wanted to testsomething other than XP, it wasdecided that agile methods would besuitable.As indicated earlier, a process isseldom based on one single model, andmodels are not considered to bemutually exclusive.Agile MethodsAgile is a common name for a numberof different software process models.Although the different models sharethe same idea, that the best way ofdeveloping software is throughoutincremental development and delivery,they propose different ways to attainthis. However, they have one morething in common, namely a set ofprinciples, which are described below2:Since evolutionary development is aprocess paradigm that provides littledetail on how to work, it would be wiseto choose a little more specific model.This model would have to agree withtheideasthatevolutionarydevelopment represents. There are twomajor process models which would besuitable; XP (eXtreme Programming)and agile development methods2. HowCustomer involvement12 (51)

3D Racing Car Game2009-05-19The customer should be closelyinvolved in the developmentprocess and contribute byproviding new system requirements and evaluate each of theiterations. In this project thedevelopers along with thesupervisor acted as customers.Incremental deliveryThe customer specifies whatrequirements are to be includedin what increment.People, not processIt is important that themembers of the developmentteam are free to develop theirown way of working, instead ofblindly following what theprocess specifies.milestone would last approximatelytwo weeks. In order to get a goodoverview and make reasonable timeestimations we, acting as developers,had two meetings per week. On thesemeetings, we checked the project’sstatus and saw to it that the milestoneswould be delivered on time. In thebeginning of each milestone, we actedas customers, thus providing newfeatures to be added. What features toadd, was based on an evaluation of themost recent milestone. For moreinformation about what tasks that wereassigned to what milestones, seeappendix A.In addition to the milestones, a roughtime estimation of the major parts ofthe game was made, this is found inappendix B.2.3. Game EngineEmbrace change2.3.1. Game FrameworkThe system should be designedin such a way, that it is easy toimplement changes or newfeatures.To save time in our developmentprocess, we choose to use MicrosoftXNA framework, when developing ourgame.Maintain simplicityMicrosoft XNAMicrosoft XNA framework providesdifferent tools to help game developersget started more quickly 4. Such tools,as the XNA Framework ContentPipeline, help developers by reducingthe time you need to add 2D and 3Dcontent to your game5. In our game, weused Microsoft XNA Game Studio 3.0,which contains a complete class libraryfor handling game content and events 6.We took advantage of many of theseclasses; Audio to implement soundeffects and background music to thegame, Graphics to implement 3Dgraphics to the game, Input toBoth development process andsoftware should be kept simple 2.MilestonesAs indicated earlier, incrementaldelivery is a keystone in agiledevelopment, which also makes it animportant part in this project. Eachincrement is here called a milestone, asa way of indicating how far on the roadto a complete program we have come.Sinceevolutionarydevelopmentstresses the importance of having shortincrements, it was decided that each13 (51)

3D Racing Car Game2009-05-19communicate with the player, and Netto implement network support to thegame.CodePlexCodePlex7 is a community to host opensource projects; most of them made in.NET, and especially C#. The website ishosted by Microsoft, and was started toencourage open source development.CodePlex provides different tools tosupport the user in his or herdevelopment; such as wiki pages,discussion forum, RSS support andstatistics(overdownloadsandvisitors). It also provides the projectwith a version control system, whichhas support for different software,including TortoiseSVN 8, and VisualStudio Team Explorer, which we usedin our project. A version control systemwas absolutely necessary for ourproject group to manage differentversions of the project files, especiallywhen many developers work with theproject concurrently.2.3.2. Physics EngineBackgroundThe part that handles the physicalbehaviour of the game world is called aphysics engine and it is made up ofthree main parts; collision detection, adynamics simulation and updating thesystem 9. The dynamic simulation partsolves the forces affecting thesimulated object.It is desirable that the game objectsbehave in a realistic way. The objectsshould be able to detect when theycollide with other objects. When theyhit another object, they should resolvethe collision in a realistic way. Theirspeed should be affected by gravity.14 (51)Each game object is represented in thephysics engine by a simplified mesh,called a collision skin. The collisionskins are often rough estimations ofthe geometry of the game object inorder to make the simulation faster.The chassis of our car objects are forexample represented by two boxes(Figure 5), one large for the bottom ofthe model and a smaller for the top.Figure 5: The car is represented by two boxesin the physics engine.Rigid body

3D Racing Car Game 2009-05-19 3 (51) Abstract This bachelor thesis describes a case study, where we focusing on developing a 3D racing car game, using a process based upon agile development; an evolutionary development method. The thesis will cover impl