diff options
Diffstat (limited to 'design.tex')
| -rw-r--r-- | design.tex | 126 |
1 files changed, 124 insertions, 2 deletions
@@ -52,11 +52,133 @@ This separation between game logic and rendering ensures that both simulation ac \subsection{Scripting} +The scripting interface was designed around a `target' \gls{api} (described by +\cref{req:script:interface,req:script:user-class,req:script:direct-instance,req:script:direct-run}). +An example of this \gls{api} is shown below:\noparbreak + +\begin{blockcode} +class MyScript : public BehaviorScript { + void update() { + // update code here + } + // init() also exists, but is empty by default +}; + +{ // in scene initialization + GameObject & obj = ...; + obj.add_component<MyScript>(); +} +\end{blockcode} + +The above call to \codeinline{GameObject::add_component} cannot work correctly +without significantly increasing the complexity of the component manager, so the +following restrictions were taken into account when creating the script system +architecture:\noparbreak + +\begin{itemize} + \item The first template parameter passed to \codeinline{GameObject::add_component} + \emph{must} be a base `script \emph{component}' class, so each derived user + script class is instantiated in the same generic script list. + \item C++ does not allow passing types (i.e.~\codeinline{MyScript} in this case) as + function parameters, so a function call like + \codeinline{add_component<BehaviorScript>(MyScript)} cannot be realized. +\end{itemize} + +\subsubsection{Architecture} + +The restrictions detailed at the start of this section are mitigated as +follows:\noparbreak + +\begin{itemize} + \item User scripts are split into two classes--- + \begin{enumerate} + \item a script \emph{interface} class (\codeinline{Script}) + \item a script \emph{component} class (\codeinline{BehaviorScript}) + \end{enumerate} + \item \codeinline{GameObject::add_component} receives the script \emph{component} + as template parameter + \item \codeinline{GameObject::add_component} now always returns a reference to the + component instance + \item The script component class has a setter function that takes a template + parameter for classes derived from the base script \emph{interface} class +\end{itemize} + +\Cref{fig:class-scripts} shows the resulting structure as a class diagram. It +contains the following classes:\noparbreak +\begin{description} + \item[Script] This is the script \emph{interface}, and is used by the game + programmer to create derived script classes. All methods in this class are + declared virtual and have an empty implementation. + + This class' methods are protected by default, and a friend relation to + \codeinline{ScriptSystem} is used to ensure only \codeinline{ScriptSystem} is + able to call these methods. + + Only classes derived from \codeinline{Script} can be used with + \codeinline{BehaviorScript::set_script}'s template parameter \codeinline{T}. This + function returns a reference to the \codeinline{BehaviorScript} instance it was + called on so it can be chained after the call to + \codeinline{GameObject::add_component}. + \item[BehaviorScript] + This is the script \emph{component}, and is given as the template parameter to + \codeinline{GameObject::add_component}. + + This class also uses a friend relation to \codeinline{ScriptSystem} to restrict + access to its private reference member \codeinline{script}. + \item[ScriptSystem] This is the system class that runs the methods implemented in + the derivative instances of \codeinline{Script}. +\end{description} + +\begin{figure} + \centering + \includepumldiag{img/class-scripts.puml} + \caption{User script class diagram} + \label{fig:class-scripts} +\end{figure} + \subsection{Audio} -\subsubsection{Library} +Since writing a custom real-time audio mixing engine is outside the scope of this +project\mref and C++ does not provide a built-in cross-platform audio \gls{api}, the +audio system inside the cr\^epe engine is implemented as a fa\c{c}ade around an +existing audio library. + +\subsubsection{Libraries} +\label{sec:audio:libs} + +This subsection compares various standalone audio libraries for suitability. After +searching for libraries (search terms: `dynamic/adaptive audio', `real-time audio', +`audio library', `game audio engine'), several libraries were found. These libraries +were checked against the audio engine requirements \autocite{crepe:requirements} and +then tested by writing the same benchmark-style \gls{poc} using the remaining +qualifying libraries:\noparbreak +\begin{enumerate} + \item Load a background track (Ogg Vorbis) + \item Load three short samples (WAV) + \item Start the background track + \item Play each sample sequentially while pausing and resuming the background track + \item Play all samples simultaniously + \item Stop all audio and exit +\end{enumerate} + +Of these libraries the following were determined to be unsuitable for use in this +project:\noparbreak +\begin{description} + \item[FMOD \autocite{lib:fmod}] Is proprietary (violates \cref{req:lib:license}). + \item[PortAudio \autocite{lib:portaudio}] Does not handle mixing. + \item[miniaudio \autocite{lib:miniaudio}] Tested by implementing a \gls{poc}, but + dropped due to very limited codec support (WAV, MP3 and FLAC only); Also does not + have an \gls{api} reference (only programming manual). + \item[YSE \autocite{lib:yse}] Attempted to write \gls{poc}, but CMake configuration + in repository is broken; This project seems to have been abandoned. +\end{description} + +The only library that remained after these tests is SoLoud \autocite{lib:soloud}. It +is Zlib/LibPng licensed and provides a high-level object-oriented C++ \gls{api}. +\Cref{sec:audio:architecture} describes the fa\c{c}ade written for this library. -\subsubsection{Fa\c{c}ade} +\subsubsection{Architecture} +\label{sec:audio:architecture} \Cref{fig:class-audio-facade} shows a class diagram of the audio fa\c{c}ade. It contains the following classes: |