82 lines
3.9 KiB
TeX
82 lines
3.9 KiB
TeX
\section{Technical Background}
|
|
|
|
The technical background is all the research related to the programming part of
|
|
this bachelor project. The programming language used in this project is a
|
|
mixture of C and C++, for this part, the course of Systems Programming taught by
|
|
Prof. Carzaniga during the third semester. Then came the study of the starting
|
|
point of the project, which was divided in the logic itself and the framework
|
|
used to display the state of the simulation on the screen.
|
|
|
|
\subsection{Original project}
|
|
|
|
Before starting to write any code, it was necessary to study carefully the
|
|
original project. The starting point chosen for this specific project was the
|
|
last commit on the \texttt{c++-port} branch. The reason for this choice is that
|
|
the project originally started fully in C (which is still the case for the
|
|
\texttt{main} branch) and C++ offers more functionalities that help for a
|
|
smoother development process.
|
|
|
|
The life-cycle of the simulation was the typical three-step process:
|
|
\begin{enumerate}
|
|
\item \textbf{State initiation:} the state of the application is set with certain
|
|
starting conditions;
|
|
\item \textbf{State update:} the state, at each frame, gets applied a set of rules that
|
|
govern the behaviour of the application;
|
|
\item \textbf{Termination:} when the user stops the application, it actuates a number
|
|
of \texttt{cleaning} up operations.
|
|
\end{enumerate}
|
|
|
|
Just like any C/C++ project, the modules were split into different files, and
|
|
those modules where themselves split into header files and implementation files.
|
|
The header files expose the public interface which other modules can call to
|
|
execute a determine function, whereas the implementation files, as the name
|
|
suggests, offer the concrete implementation of the aforementioned functions. The
|
|
implementation files can use some static\footnote{static in the sense of C,
|
|
i.e. visible only to the file it is declared in} functions that it can use
|
|
as auxiliary or utility functions. The header files usually expose the fields
|
|
and methods of the class (or \texttt{struct}) the module is using, if any, together
|
|
with one function for each of three steps of the life-cycle mentioned above.
|
|
|
|
\subsection{Cairo}
|
|
|
|
Cairo is a 2D graphics library with support for multiple output devices. Cairo
|
|
is designed to produce consistent output on all output media while taking
|
|
advantage of display hardware acceleration when available. The cairo API
|
|
provides operations similar to the drawing operators of PostScript and PDF.
|
|
Operations in cairo including stroking and filling cubic Bézier splines,
|
|
transforming and compositing translucent images, and antialiased text rendering.
|
|
All drawing operations can be transformed by any affine transformation (scale,
|
|
rotation, shear, etc.). Reading the
|
|
documentation\footnote{\url{https://www.cairographics.org/documentation/}}, and
|
|
more specifically the practical
|
|
tutorial\footnote{\url{https://www.cairographics.org/tutorial/}} was useful to
|
|
understand how the library works.
|
|
|
|
|
|
|
|
The Cairo drawing model relies on a three-layer model, any drawing process takes
|
|
place in three steps:
|
|
|
|
\begin{minipage}{.5\textwidth}
|
|
\begin{enumerate}
|
|
\item first a mask is created, which includes one or more vector
|
|
primitives or forms, i.e., circles, squares, TrueType fonts, Bézier
|
|
curves, etc;
|
|
|
|
\item then source must be defined, which may be a color, a color
|
|
gradient, a bitmap or some vector graphics, and from the painted
|
|
parts of this source a die cut is made with the help of the above
|
|
defined mask;
|
|
|
|
\item finally the result is transferred to the destination or surface,
|
|
which is provided by the back-end for the output.
|
|
\end{enumerate}
|
|
\end{minipage}
|
|
\begin{minipage}{.49\textwidth}
|
|
\centering
|
|
\includegraphics[width=0.8\textwidth]{cairo}
|
|
\captionof{figure}{Cairo's drawing model\protect\footnotemark}
|
|
\label{fig:cairo}
|
|
\end{minipage}
|
|
\footnotetext{Image taken from Wikipedia}
|