more stage clarifications

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Motiejus Jakštys 2021-05-19 22:57:47 +03:00 committed by Motiejus Jakštys
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@ -5,7 +5,9 @@
\usepackage[english]{babel} \usepackage[english]{babel}
\usepackage[utf8]{inputenc} \usepackage[utf8]{inputenc}
\usepackage{a4wide} \usepackage{a4wide}
\usepackage{csquotes} %\usepackage{csquotes}
\usepackage [autostyle, english = american]{csquotes}
\MakeOuterQuote{"}
\usepackage[maxbibnames=99,style=authoryear]{biblatex} \usepackage[maxbibnames=99,style=authoryear]{biblatex}
\usepackage[pdfusetitle]{hyperref} \usepackage[pdfusetitle]{hyperref}
\usepackage{enumitem} \usepackage{enumitem}
@ -270,24 +272,53 @@ purposes) using the following algorithm:
\section{Definition of a Bend} \section{Definition of a Bend}
\label{sec:definition-of-a-bend} \label{sec:definition-of-a-bend}
The original article describes:
\begin{displayquote}[\cite{wang1998line}][]
A bend can be defined as that part of a line which contains a number of
subsequent vertices, with the inflection angles on all vertices included in
the bend being either positive or negative and the inflection of the bend's
two end vertices being in opposite signs.
\end{displayquote}
While it gives a good intuitive understanding of what the bend is, some more
technical details would be appreciated.
Figure~\ref{fig:fig8-definition-of-a-bend} illustrates article's figure 8,
but with bends colored as polygons: each color is a distinctive bend.
\begin{figure}[h] \begin{figure}[h]
\centering \centering
\includegraphics[width=\linewidth]{fig8-definition-of-a-bend} \includegraphics[width=\linewidth]{fig8-definition-of-a-bend}
\caption{Originally Figure 8: detected bends are highlighted} \caption{Originally figure 8: detected bends are highlighted}
\label{fig:fig8-definition-of-a-bend} \label{fig:fig8-definition-of-a-bend}
\end{figure} \end{figure}
End line segments of all lines should also be part of the bend. That way, all Once the intuitive definition is established, here are some non-obvious
line segments belong to 1 or 2 bends. This characteristic is not obvious when characteristics that are necessary when writing code to detect the bends:
reading the introductory sections, but becomes unavoidable (there could be no
other way) when reading the following sections in detail.
First and last segments of each bend (except for the two end-line segments) is \begin{itemize}
also the first vertex of the next bend. This is apparent when looking at the
illustration of the detected bends. \item End segments of each line should also belong to bends. That way, all
segments belong to 1 or 2 bends.
\item First and last segments of each bend (except for the two end-line
segments) is also the first vertex of the next bend.
\end{itemize}
Properties above may be apparent when looking at illustrations at this article
or reading here, but they are nowhere as such when looking at the original
article.
\section{Gentle Inflection at End of a Bend} \section{Gentle Inflection at End of a Bend}
The gist of the section is in the original article:
\begin{displayquote}[\cite{wang1998line}][]
But if the inflection that marks the end of a bend is quite small, people
would not recognize this as the bend point of a bend
\end{displayquote}
Figure~\ref{fig:fig5-gentle-inflection} visualizes original paper's Figure 5, Figure~\ref{fig:fig5-gentle-inflection} visualizes original paper's Figure 5,
when a single vertex is moved outwards the end of the bend. when a single vertex is moved outwards the end of the bend.
@ -302,20 +333,21 @@ when a single vertex is moved outwards the end of the bend.
\includegraphics[width=\textwidth]{fig5-gentle-inflection-after} \includegraphics[width=\textwidth]{fig5-gentle-inflection-after}
\caption{After applying the inflection rule} \caption{After applying the inflection rule}
\end{subfigure} \end{subfigure}
\caption{Originally Figure 5: gentle inflections at the ends of the bend} \caption{Originally figure 5: gentle inflections at the ends of the bend}
\label{fig:fig5-gentle-inflection} \label{fig:fig5-gentle-inflection}
\end{figure} \end{figure}
The example in this section was clear, but insufficient: it does not specify The illustration for this section was clear, but insufficient: it does not
how many vertices should be included when calculating the end-of-bend specify how many vertices should be included when calculating the end-of-bend
inflection. We chose the iterative approach -- as long as the angle is "right" inflection. We chose the iterative approach --- as long as the angle is "right"
and the distance is decreasing, the algorithm should keep re-assigning vertices and the distance is decreasing, the algorithm should keep re-assigning vertices
to different bends; practically not having an upper bound on the number of to different bends; practically not having an upper bound on the number of
iterations. iterations.
Additional example, not found in the original paper, is illustrated in To prove that the algorithm implementation is correct for multiple vertices,
figure~\ref{fig:inflection-1-gentle-inflection}, which re-assigns two vertices additional example was created, and illustrated in
to the next bend instead of one. figure~\ref{fig:inflection-1-gentle-inflection}: the rule re-assigns two
vertices to the next bend instead of one.
\begin{figure}[h] \begin{figure}[h]
\centering \centering