% thanks for the template:
% http://www.texample.net/tikz/examples/simple-flow-chart/
\documentclass{standalone}
\usepackage{gensymb}
%\usepackage[pdftex,active,tightpage]{preview}
%\setlength\PreviewBorder{2mm}

\usepackage[utf8]{inputenc} % this is needed for umlauts
\usepackage[ngerman]{babel} % this is needed for umlauts
\usepackage[T1]{fontenc}    % this is needed for correct output of umlauts in pdf
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}

\begin{document}
%\begin{preview}

% Define block styles
\tikzstyle{decision} = [diamond, draw, fill=blue!20,
    text width=4.5em, text badly centered, node distance=3cm, inner sep=0pt]
\tikzstyle{block} = [rectangle, draw, fill=blue!20,
    text width=5em, text centered, rounded corners, minimum height=4em]
\tikzstyle{line} = [draw, -latex']

\begin{tikzpicture}[auto]
    % Place nodes
    \node [block] (init) {start};
    \node [decision, below of=init] (boundingBoxes) {do bounding boxes intersect?};
    \node [decision, right of=boundingBoxes, node distance=4cm] (lineAIntersectLineB) {does line a intersect line segment b?};
    \node [decision, right of=lineAIntersectLineB, node distance=4.7cm] (lineBIntersectLineA) {does line b intersect line segment a?};
    \node [block, right of=lineBIntersectLineA, node distance=4.7cm] (yes) {yes};
    \node [block, below of=boundingBoxes, node distance=3cm] (no) {no};
    % Draw edges
    \path [line] (init) -- (boundingBoxes);
    \path [line] (boundingBoxes) -- node {no}(no);
    \path [line] (boundingBoxes) -- node {yes}(lineAIntersectLineB);
    \path [line] (lineAIntersectLineB) |- node {no}(no);
    \path [line] (lineAIntersectLineB) -- node {yes}(lineBIntersectLineA);
    \path [line] (lineBIntersectLineA) |- node {no}(no);
    \path [line] (lineBIntersectLineA) -- node {yes}(yes);
\end{tikzpicture}
%\end{preview}
\end{document}