When I use \draw to create a grid, several lines are missing. See the attached code and images, where, for example, the dashed red grid is missing the bottom and left boundaries. Actually the solid green and solid red gird are missing it as well. I'm not sure if I am getting graphical bugs or if this is intended behavior:
\documentclass{article}
\usepackage{tikz}
\pagestyle{empty}
\pgfdeclarelayer{level0}
\pgfdeclarelayer{level1}
\pgfdeclarelayer{level2}
\pgfsetlayers{main,level0,level1,level2}
\begin{document}
\begin{figure}[h]
\centering
\begin{tikzpicture}[scale=2]
\begin{pgfonlayer}{level0} % Level 0
\draw[help lines] (0,0) grid (5,5); % Base grid
\draw[very thick, scale=5] (0,0) grid (1,1); % Darker lines to mark e.g. box boundaries
\end{pgfonlayer}
\begin{pgfonlayer}{level1} % Level 1
\draw[green, dashed] (.5,.5) grid[step=.5] (4.5,4.5); % Ghost cells
\draw[green] (1,1) grid[step=.5] (4,4);
\end{pgfonlayer}
\begin{pgfonlayer}{level2} % Level 2
\draw[red, dashed] (1.75,1.75) grid[step=.25] (3.25,3.25); % Ghost cells
\draw[red] (2,2) grid[step=.25] (3,3);
\end{pgfonlayer}
\end{tikzpicture}
\caption{Standard isotropic refinement.}
\end{figure}
\end{document}
Thank you!