[Tex/LaTex] Horizontally align subfloat in figure

Question

I am putting three figures on one row, and the width is not enough if I want to show them clearly (big enough). I used to use hspace to manually shift the figure, but it doesn't work this time. (It only affects the first row.) How could I shift the whole figure? I need to left shift the whole figure for certain distance for this page, I think.

This is one MWE do illustrate the problem:

\documentclass{article}
\usepackage[demo]{graphicx}
\usepackage{subfig}
\begin{document}
\newcommand{\IDCTFigureHeight}{2.8}
\begin{figure}[p]
  \vspace{-10pt}
  \subfloat[v1 with buffer size 16]{\includegraphics[width=0.45\textwidth,height=\IDCTFigureHeight in]{images/local/v1_16.png}}
  \subfloat[v1 with buffer size 100]{\includegraphics[width=0.45\textwidth,height=\IDCTFigureHeight in]{images/local/v1_100.png}}
  \subfloat[v1 with buffer size 200]{\includegraphics[width=0.45\textwidth,height=\IDCTFigureHeight in]{images/local/v1_200.png}}
  \vspace{-10pt}
  \\
  \subfloat[v2 with buffer size 16]{\includegraphics[width=0.45\textwidth,height=\IDCTFigureHeight in]{images/local/v2_16.png}}
  \subfloat[v2 with buffer size 100]{\includegraphics[width=0.45\textwidth,height=\IDCTFigureHeight in]{images/local/v2_100.png}}
  \subfloat[v2 with buffer size 200]{\includegraphics[width=0.45\textwidth,height=\IDCTFigureHeight in]{images/local/v2_200.png}}
  \vspace{-10pt}
  \\
  \subfloat[v3 with buffer size 16]{\includegraphics[width=0.45\textwidth,height=\IDCTFigureHeight in]{images/local/v3_16.png}}
  \subfloat[v3 with buffer size 100]{\includegraphics[width=0.45\textwidth,height=\IDCTFigureHeight in]{images/local/v3_100.png}}
  \subfloat[v3 with buffer size 200]{\includegraphics[width=0.45\textwidth,height=\IDCTFigureHeight in]{images/local/v3_200.png}}
  \caption{destination-fifo with different buffer size.}
\end{figure}
\end{document}

Answer 1

You can add also \hspace to the second and third rows if you use a blank line or \par instead of \\. That is, change:

\vspace{-10pt}
\\

by

\vspace{-10pt}


\hspace{-2cm}

or

\vspace{-10pt}\par    
\hspace{-2cm}