# Tikzpicture: Fill refuses to work with integer node names [duplicate]

This question already has an answer here:

I want to create a 3D-grid of named nodes using nested for loops and then fill some polygon based on the names. For some reason tikzpicture doesn't fill the polygon, although it draws the path alright.

I assume it has something to do with the node names. Here is a minimal 2D-example:

\begin{tikzpicture}

\foreach \i in {0,...,3} {
\foreach \j in {0,...,3} {
\node at (\i, \j) (\i\j) {};
}}

\draw (00) -- (02) -- (12);
\fill (00) -- (02) -- (12);

\end{tikzpicture}


The output is the grid, with two lines but no fill.