This is the LaTeX source for drawing diagrams for two kinds of (syntactic) alignment --- ergative-absolutive and nominative-accusative. The pgf/tikz package is required.

alignment-diagrams.tex

\documentclass[14pt]{scrartcl}

\usepackage{subfigure}
\usepackage{tikz}

    \usetikzlibrary{arrows,backgrounds,calc,fit,matrix,positioning,
                    shapes,shapes.geometric,shapes.misc}
\pgfdeclarelayer{foreground} 
\pgfdeclarelayer{background}
   \pgfsetlayers{background,%
                 main,%
                 foreground%
                 }

\begin{document}

\begin{figure}[h]
  \centering
  \subfigure[Ergative-absolutive]{\label{Ergative-absolutive}
    \begin{tikzpicture}[
     buffer/.style = {
        isosceles triangle,
        isosceles triangle apex angle=66,
        shape border rotate=90,%
        %fill=blue!20, opacity=0.6,
        node distance=2em,
        rounded corners=60pt,
        minimum height=2.5em},
frames/.style args = {#1/#2}{minimum height=#1,
               minimum width=#2+\pgfkeysvalueof{/pgf/minimum height},
               draw, rounded corners=5mm, fill=pink, opacity=0.6,
               sloped}, 
                        ]
    \begin{pgfonlayer}{foreground}
\node (A)  at (0,0)    {S};
\node (B)  at (-2,-3)  {A};
\node (C)  at (2,-3)   {O};
    \end{pgfonlayer}
    \begin{pgfonlayer}{main}
\path   let \p1 = ($(C.center)-(A.center)$),
            \n1 = {veclen(\y1,\x1)} in
            (A) -- 
            node[frames=11mm/\n1] {} (C);
    \end{pgfonlayer}
    \begin{pgfonlayer}{background}
\node[buffer]at (0,-1.9){};
    \end{pgfonlayer}
  \end{tikzpicture}
}\hspace*{5em}
\subfigure[Nominative-accusative]{\label{Nominative-accusative}
    \begin{tikzpicture}[
     buffer/.style = {
        isosceles triangle,
        isosceles triangle apex angle=66,
        shape border rotate=90,%
        %fill=blue!20, opacity=0.6,
        node distance=2em,
        rounded corners=60pt,
        minimum height=2.5em},
frames/.style args = {#1/#2}{minimum height=#1,
               minimum width=#2+\pgfkeysvalueof{/pgf/minimum height},
               draw, rounded corners=5mm, fill=pink, opacity=0.6,
               sloped}, 
                        ]
    \begin{pgfonlayer}{foreground}
\node (A)  at (0,0)    {S};
\node (B)  at (-2,-3)  {A};
\node (C)  at (2,-3)   {O};
    \end{pgfonlayer}
    \begin{pgfonlayer}{main}
\path   let \p1 = ($(B.center)-(A.center)$),
            \n1 = {veclen(\y1,\x1)} in
            (A) -- 
            node[frames=11mm/\n1] {} (B);
    \end{pgfonlayer}
    \begin{pgfonlayer}{background}
\node[buffer]at (0,-1.9){};
    \end{pgfonlayer}
  \end{tikzpicture}
  }
\end{figure}

\end{document}