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@@ -23,10 +23,92 @@ Unity and are looking for a flexible, cost-effective solution with familiar workflows. \section{Overview} +As described above, the cr\^epe game engine's goal is to offer a Unity-like experience +tailored for developing 2D games similar to Jetpack Joyride. That is why Jetpack +Joyride and Unity provided the main inputs for this game engine design. Firstly, a +quick overview will be given of the Unity game engine, in particular the \gls{ecs}. +Secondly, this Overview will quickly talk you through some of the most important +parts of the game engine, and why these parts are needed to create the Jetpack +Joyride game. + +\subsection{ECS} +The Unity game engine is structured using the Entity Component System (\gls{ecs}) +(as shown in \cref{fig:ECS Block Diagram}). The \gls{ecs} is made out of three +main subsystems, namely entities, components and systems. Entities are just IDs. +An entity is also called a GameObject in Unity and it is made out of one (or +more) components. Components are the classes that hold the data. The components +determine what kind of entity it is (e.g. an enemy, audio, and so on). Systems take +care of the behavior of the entities. Systems mainly read and write the enity's +components data. The \gls{ecs} clearly distinguishes the data (components) from the +functionality (systems). -\subsection{Core} +\begin{figure} + \centering + \includegraphics[width=0.5\textwidth]{img/ECSBlockDiagram.png} + \caption{ECS design pattern} + Source: \autocite{img:ECSBlockDiagram} + \label{fig:ECS Block Diagram} +\end{figure} + +The \gls{ecs} will also be used at the cr\^epe game engine. Everything (from the +protagonist and bullets to the walls and enemies) in the cr\^epe game engine will +be a GameObject (a.k.a. entity). The game programmer must program his game by +creating all kind of GameObjects and placing them in one (or multiple) scenes, just +like Unity. + +\subsection{Jetpack Joyride} +Firstly, some background information about Jetpack Joyride. Jetpack Joyride is a +side-scrolling endless runner action video game created by Halfbrick Studios. The +protagonist is called Barry Steakfries, who the player controls as he steals a +bullet-powered jet pack from a top-secret laboratory \autocite{wiki:JetpackJoyride}. +A screenshot from the game can be seen in \cref{fig:JetpackJoyride} (pleae be +aware that the goal of this project is not to create an exact replica of Jetpack +Joyride, it is only used as a source of inspiration). + +\begin{figure} + \centering + \includegraphics[width=0.5\textwidth]{img/JetpackJoyride.jpg} + \caption{Jetpack Joyride} + Source: \autocite{img:JetpackJoyride} + \label{fig:JetpackJoyride} +\end{figure} -\subsection{Patterns} +The protagonist wears a jetpack with which he can float in the air. The player must +avoide obstacles (such as lasers, missiles and zappers) by floating at the right +height. The player can control the protagonist's jetpack, thereby also controlling +the protagonist's height. The protagonist experiences gravity and other forces (like +the force from his jetpack pushing him upwards). These forces should be easily +programmable by the game programmer. That is why a physics system is needed in the +cr\^epe game engine. Only very limited/easy physics are needed for Jetpack Joyride, +that is why this is only supported by the cr\^epe game engine. + +The protagonist must avoid obstacles. That is why the cr\^epe game engine should +also support a collision system. Again, only very limited/easy collision is needed +for Jetpack Joyride, that is why only very limited/easy collision is supported +by the cr\^epe game engine. + +The game must, of course, also be visible to and playable by the user. A rendering +system will take care of rendering (displaying) the game and its GameObjects. An +input system will take care of all the inputs (mouse and keyboard). + +Jetpack Joyride also offers audio. A system will take care of the audio in the cr\^epe +game engine. + +Particles are very common in Jetpack Joyride, e.g. underneath the jetpack and behind +the rockets. Particles will be supported by the particle system. + +The start of a scene is described in a scene. However, the game programmer might also +want to write game logic code which is running during the game (e.g. to switch to a +new scene or to perform a custom action at a collision). For these purposes, Unity +uses scripts. These scripts will also be supported by the cr\^epe game engine. + +Finally, as an extra, replay functionality will be supported by the cr\^epe game +engine. A dedicated replay system will be used to support replay. + +It turns out that a physics, collision, rendering, input, audio, particle, script, +and replay system are needed to create the Jetpack Joyride game. These systems form +the main part of the \gls{ecs}. The design of these eight systems in combination with +\gls{ecs}, will be briefly discussed in the next parts of this design document. \section{Design} |