我的图形第二行不在中心

Question

我正在使用 minipage 在 pdf 文件中显示我的图表，代码如下：

\begin{figure*}[tb] 
\begin{minipage}[b]{.28\linewidth}
    \centering
    \includegraphics[width=\columnwidth]{images/3_tech/rollercoaster.jpg}
    \centerline{(a) Mega Coaster}\medskip
\end{minipage}
\begin{minipage}[b]{.28\linewidth}
    \centering
    \includegraphics[width=\columnwidth]{images/3_tech/LeagueofLegends.jpg}
    \centerline{(b) Project 360}\medskip        
\end{minipage}
\begin{minipage}[b]{0.28\linewidth}
    \centering
    \includegraphics[width=\columnwidth]{images/3_tech/Cockpit.jpg}
    \centerline{(c) 360 Cockpit View}\medskip
\end{minipage}
\begin{minipage}[b]{.28\linewidth}
    \centering
    \includegraphics[width=\columnwidth]{images/3_tech/SkyDiving.jpg}
    \centerline{(d) Sky Diving}\medskip
\end{minipage}
\begin{minipage}[b]{.28\linewidth}
    \centering
    \includegraphics[width=\columnwidth]{images/3_tech/Etihad.jpg}
    \centerline{(e) Etihad A380}\medskip
\end{minipage}
\begin{minipage}[b]{0.28\linewidth}
    \centering
    \includegraphics[width=\columnwidth]{images/3_tech/Elephants.jpg}
    \centerline{(f) Elephants}\medskip
\end{minipage}
\caption{Sample 2D representation scenes of 360$^\circ$ videos used in Test 1.}
\label{fig:Dataset_T1}
\end{figure*}

输出如下所示：

我该怎么做才能使第二行看起来像第一行。