Tikz - Randomly fill 3D grid with color shades

Question

I'm trying to create a "3D" schema of a grid where every "pixel" is colored with a random shade of blue (or whatever other color). As a tikz beginner, I'm already glad that I managed to tilt the grid, but so far I only managed to change the color for the whole grid. This is my MWE:

\documentclass{standalone}
\usepackage{tikz}
\usepackage{xcolor}
\begin{document}
    \begin{tikzpicture}[every node/.style={minimum size=1cm}]
        \begin{scope}[
            every node/.append style={
                yslant=0.5, xslant=-1}, yslant=0.5, xslant=-1
            ]
            \fill[blue, fill opacity=.6] (0,0) rectangle (5.5, 5.5);
            \draw[gray, very thick] (0,0) rectangle (5.5, 5.5);
            \draw[step=5mm, gray] (0,0) grid (5.5, 5.5);
        \end{scope}
    \end{tikzpicture}
\end{document}

From what I saw in other posts, I fear I need to draw every pixel on its own?

Answer 1

You can use two nested \foreach sentences for rows and columns and compute inside the loops a random number for each element in the grid.

I changed your approach for the 3d view, using 3d and perspective TikZ libraries, but the \foreach method is also valid with your example.

For example,

\documentclass[tikz,border=2mm]{standalone}
\usetikzlibrary{3d,perspective}

\begin{document}
\begin{tikzpicture}[isometric view, canvas is xy plane at z=0]
  \foreach\i in {0,0.5,...,5} \foreach\j in {0,0.5,...,5}
    \pgfmathparse{100*rnd}
    \fill[blue!\pgfmathresult,draw=gray] (\i,\j) rectangle (\i+0.5,\j+0.5);
  \draw[gray, very thick] (0,0,0) rectangle (5.5, 5.5,0);
\end{tikzpicture}
\end{document}