Add dots in a specific position inside tikzpicture

Question

I have written the following code:

\documentclass[margin=5mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{matrix,calc}

\begin{document}
\begin{tikzpicture}[every node/.style={anchor=north east,fill=white,minimum width=1.4cm,minimum height=7mm}]
\matrix (mA) [draw,matrix of math nodes]
{
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
};

\matrix (mB) [draw,matrix of math nodes] at ($(mA.south west)+(1.5,0.7)$)
{
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
};

\matrix (mC) [draw,matrix of math nodes] at ($(mB.south west)+(1.5,0.7)$)
{
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
};

\draw[dashed](mA.north east)--(mC.north east);
\draw[dashed](mA.north west)--(mC.north west);
\draw[dashed](mA.south east)--(mC.south east);
\end{tikzpicture}


\end{document}

which produces the image below: ]1

How can I add some dots (using for example \dots) in the bottom left triangle generated by the dashed line, the bottom matrix and the middle matrix?

Answer 1

Welcome! The nodes inside matrices get automatically names. For instance, the nodes in the matrix mB have names mB-<row>-<column>. This can be used as in

\documentclass[margin=5mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{matrix,calc}

\begin{document}
\begin{tikzpicture}
\begin{scope}[every node/.style={anchor=north east,fill=white,minimum width=1.4cm,minimum height=7mm}]
\matrix (mA) [draw,matrix of math nodes]
{
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
};

\matrix (mB) [draw,matrix of math nodes] at ($(mA.south west)+(1.5,0.7)$)
{
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
};

\matrix (mC) [draw,matrix of math nodes] at ($(mB.south west)+(1.5,0.7)$)
{
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
(1,1,3) & (1,1,3) & (1,1,3) & (1,1,3) \\
};
\end{scope}
\draw[dashed](mA.north east)--(mC.north east);
\draw[dashed](mA.north west)--(mC.north west);
\draw[dashed](mA.south east)--(mC.south east);
\path (mB-4-2) -- (mB-4-3) node[midway,below=2em]{$\vdots$};
\end{tikzpicture}
\end{document}