Is there an easy way to draw isometric objects with shading

Question

I would like to draw a diagram like this:

I have started trying to draw it using the code from here and this is what I have:

documentclass[tikz,border=2mm]{standalone}
\usetikzlibrary{shapes}

\tikzset{
    iso/.style={kite, draw, kite vertex angles=120,  minimum size=1cm, outer sep=0pt}
}

\newcommand{\isogrid}[2]{
\foreach \i [count=\row from 0, remember=\row as \lastrow (initially 0)] in {0,...,#1}{
    \foreach \j [count=\col from 0, remember=\col as \lastcol (initially 0)] in {0,...,#2}{
        \ifnum\row=0
            \ifnum\col=0
                \node[iso] (\row-\col) {\row-\col};
            \else
                \node[iso, anchor=left vertex] (\row-\col) at (\row-\lastcol.right vertex) {\row-\col};
            \fi
        \else
            \ifnum\col=0
                \node[iso, anchor=upper vertex] (\row-\col) at (\lastrow-\col.lower vertex) {\row-\col};
            \else
                \node[iso, anchor=left vertex] (\row-\col) at (\row-\lastcol.right vertex) {\row-\col};
            \fi
        \fi
        }
    }
\draw (0-0.left vertex)--(#1-0.left vertex);
\foreach \i in {0,...,#2}{
    \draw (0-\i.upper vertex)--(#1-\i.lower vertex);
    \draw (0-\i.right vertex)--(#1-\i.right vertex);
}
}

\begin{document}
\begin{tikzpicture}
\isogrid{3}{3}
    \draw[fill=red!70!black] (3-0.left vertex) -- (0-0.left vertex) -- (0-0.lower vertex) -- (3-0.lower vertex) -- cycle;
    \draw[fill=red!40!black] (0-0.lower vertex) -- (0-0.right vertex) -- (3-0.right vertex) -- (3-0.lower vertex);
    \draw[fill=red!80!white] (0-0.lower vertex) -- (0-0.left vertex) -- (0-0.upper vertex) -- (0-0.right vertex) -- cycle;
\end{tikzpicture}
\end{document}

I was wondering if there is a package or an easier way to draw these kind of diagrams

Answer 1

There is, to the best of my knowledge, no explicit package. However, there is an answer that one can use.

\documentclass[tikz,border=3.14mm]{standalone}
% from https://tex.stackexchange.com/a/499703
\definecolor{redxy}{RGB}{214,106,77}
\definecolor{redxz}{RGB}{185,90,66}
\definecolor{redyz}{RGB}{149,61,38}
\usepackage{tikz-3dplot}
\tikzset{plane/.style n args={3}{insert path={%
#1 -- ++ #2 -- ++ #3 -- ++ ($-1*#2$) -- cycle}},
unit xy plane/.style={plane={#1}{(\CubeX,0,0)}{(0,\CubeY,0)}},
unit xz plane/.style={plane={#1}{(\CubeX,0,0)}{(0,0,\CubeZ)}},
unit yz plane/.style={plane={#1}{(0,\CubeY,0)}{(0,0,\CubeZ)}},
get projections/.style={insert path={%
let \p1=(1,0,0),\p2=(0,1,0)  in 
[/utils/exec={\pgfmathtruncatemacro{\xproj}{sign(\x1)}\xdef\xproj{\xproj}
\pgfmathtruncatemacro{\yproj}{sign(\x2)}\xdef\yproj{\yproj}
\pgfmathtruncatemacro{\zproj}{sign(cos(\tdplotmaintheta))}\xdef\zproj{\zproj}}]}},
pics/unit cube/.style={code={
\path[get projections];
\ifnum\zproj=-1
 \path[3d cube/every face,3d cube/xy face,unit xy plane={(-\CubeX/2,-\CubeY/2,-\CubeZ/2)}]; 
\else 
 \path[3d cube/every face,3d cube/xy face,unit xy plane={(-\CubeX/2,-\CubeY/2,\CubeZ/2)}]; 
\fi
\ifnum\yproj=1
 \path[3d cube/every face,3d cube/yz face,unit yz plane={(-\CubeX/2,-\CubeY/2,-\CubeZ/2)}]; 
\else
 \path[3d cube/every face,3d cube/yz face,unit yz plane={(\CubeX/2,-\CubeY/2,-\CubeZ/2)}]; 
\fi
\ifnum\xproj=1
 \path[3d cube/every face,3d cube/xz face,unit xz plane={(-\CubeX/2,\CubeY/2,-\CubeZ/2)}]; 
\else
 \path[3d cube/every face,3d cube/xz face,unit xz plane={(-\CubeX/2,-\CubeY/2,-\CubeZ/2)}]; 
\fi
\ifnum\yproj=1
 \path[3d cube/every face,3d cube/yz face,unit yz plane={(\CubeX/2,-\CubeY/2,-\CubeZ/2)}]; 
\else
 \path[3d cube/every face,3d cube/yz face,unit yz plane={(-\CubeX/2,-\CubeY/2,-\CubeZ/2)}]; 
\fi
\ifnum\xproj=1
 \path[3d cube/every face,3d cube/xz face,unit xz plane={(-\CubeX/2,-\CubeY/2,-\CubeZ/2)}]; 
\else
 \path[3d cube/every face,3d cube/xz face,unit xz plane={(-\CubeX/2,\CubeY/2,-\CubeZ/2)}]; 
\fi
\ifnum\zproj>-1
 \path[3d cube/every face,3d cube/xy face,unit xy plane={(-\CubeX/2,-\CubeY/2,\CubeZ/2)}]; 
\else 
 \path[3d cube/every face,3d cube/xy face,unit xy plane={(-\CubeX/2,-\CubeY/2,-\CubeZ/2)}]; 
\fi
}},
3d cube/.cd,
xy face/.style={fill=red!20},
xz face/.style={fill=blue!20},
yz face/.style={fill=orange!30},
num cubes x/.estore in=\NumCubesX,
num cubes y/.estore in=\NumCubesY,
num cubes z/.estore in=\NumCubesZ,
num cubes x/.initial=1,num cubes y/.initial=1,num cubes z/.initial=1,
cube x/.estore in=\CubeX,
cube y/.estore in=\CubeY,
cube z/.estore in=\CubeZ,
cube x=1,cube y=1,cube z=1,
cube scale/.initial=1,
every face/.style={draw,very thick},
/tikz/pics/.cd,
cube array/.style={code={%
 \tikzset{3d cube/.cd,#1}
 %\typeout{\NumCubesX,\NumCubesY,\NumCubesZ}
  \path[get projections];
  \ifnum\yproj=1
   \def\LstX{1,...,\NumCubesX}
  \else 
   \ifnum\NumCubesX>1
    \pgfmathtruncatemacro{\NextToLast}{\NumCubesX-1}
    \def\LstX{\NumCubesX,\NextToLast,...,1}
   \else
    \def\LstX{1}   
   \fi 
  \fi
  \ifnum\xproj=-1
   \def\LstY{1,...,\NumCubesY}
  \else 
   \ifnum\NumCubesY>1
    \pgfmathtruncatemacro{\NextToLast}{\NumCubesY-1}
    \def\LstY{\NumCubesY,\NextToLast,...,1}
   \else
    \def\LstY{1}   
   \fi 
  \fi
  \ifnum\zproj=1
   \def\LstZ{1,...,\NumCubesZ}
  \else 
   \ifnum\NumCubesZ>1
    \pgfmathtruncatemacro{\NextToLast}{\NumCubesZ-1}
    \def\LstZ{\NumCubesZ,\NextToLast,...,1}
   \else
    \def\LstZ{1}   
   \fi 
  \fi
  \foreach \X in \LstX
  {\foreach \Y in \LstY
   {\foreach \Z in \LstZ
    {\path (\X-1/2,\Y-1/2,\Z-1/2)
      pic[scale=\pgfkeysvalueof{/tikz/3d cube/cube scale}]{unit cube};}}
  } 
}}
}

\begin{document}
\tdplotsetmaincoords{70}{50} % the first argument cannot be larger than 90
\begin{tikzpicture}[line join=round,tdplot_main_coords,font=\sffamily,3d cube/.cd,
 num cubes x=1,num cubes y=1,num cubes z=1]
\begin{scope}[3d cube/.cd,every face/.style={draw=none},
    xy face/.style={fill=redxy},xz face/.style={fill=redxz},yz face/.style={fill=redyz}] 
% top left
 \path (0,0,0) pic{cube array={num cubes y=2,num cubes z=3}}
  (0,-1,0) pic{cube array={num cubes y=1,num cubes z=1}}
  (1,0,0) pic{cube array={num cubes y=2,num cubes z=2}}
  (1,1,2) pic{cube array={num cubes y=1,num cubes z=1}}
  (2,1,0) pic{cube array={num cubes y=1,num cubes z=1}}
 ;
\end{scope}
\end{tikzpicture}
\end{document}

For the isometric view choose

 \tdplotsetmaincoords{90-35.26}{45}

You can choose the view angles rather freely. For very different view angles one needs to put the arrays in a different order.

You can also use this answer, which is based on this answer.

\documentclass[tikz,border=3.14mm]{standalone}
\definecolor{redxy}{RGB}{214,106,77}
\definecolor{redxz}{RGB}{185,90,66}
\definecolor{redyz}{RGB}{149,61,38}
\usepackage{tikz-3dplot}
\usetikzlibrary{backgrounds}
\newcounter{x}
\newcounter{y}
\newcounter{z}
\tikzset{plane/.style n args={3}{insert path={%
#1 -- ++ #2 -- ++ #3 -- ++ ($-1*#2$) -- cycle}},
unit xy plane/.style={plane={#1}{(1,0,0)}{(0,1,0)}},
unit xz plane/.style={plane={#1}{(1,0,0)}{(0,0,1)}},
unit yz plane/.style={plane={#1}{(0,1,0)}{(0,0,1)}},
get projections/.style={insert path={%
let \p1=(1,0,0),\p2=(0,1,0)  in 
[/utils/exec={\pgfmathtruncatemacro{\xproj}{sign(\x1)}\xdef\xproj{\xproj}
\pgfmathtruncatemacro{\yproj}{sign(\x2)}\xdef\yproj{\yproj}
\pgfmathtruncatemacro{\zproj}{sign(cos(\tdplotmaintheta))}\xdef\zproj{\zproj}}]}},
pics/unit cube/.style={code={
\path[get projections];
\draw (0,0,0) -- (1,1,1);
\ifnum\zproj=-1
 \path[3d cube/every face,3d cube/xy face,unit xy plane={(0,0,0)}]; 
\fi
\ifnum\yproj=1
 \path[3d cube/every face,3d cube/yz face,unit yz plane={(1,0,0)}]; 
\else
 \path[3d cube/every face,3d cube/yz face,unit yz plane={(0,0,0)}]; 
\fi
\ifnum\xproj=1
 \path[3d cube/every face,3d cube/xz face,unit xz plane={(0,0,0)}]; 
\else
 \path[3d cube/every face,3d cube/xz face,unit xz plane={(0,1,0)}]; 
\fi
\ifnum\zproj>-1
 \path[3d cube/every face,3d cube/xy face,unit xy plane={(0,0,1)}]; 
\fi
}},
3d cube/.cd,
xy face/.style={fill=red!20},
xz face/.style={fill=blue!20},
yz face/.style={fill=orange!30},
num cubes x/.estore in=\NumCubesX,
num cubes y/.estore in=\NumCubesY,
num cubes z/.estore in=\NumCubesZ,
num cubes x=1,num cubes y/.initial=1,num cubes z/.initial=1,
cube scale/.initial=0.9,
every face/.style={draw,very thick},}

\newcommand\Planepartition[1]{
 \setcounter{x}{0}\setcounter{y}{0}\setcounter{z}{0}
 \foreach \Lst [count=\Z starting from 0] in {#1} {
  \pgfmathtruncatemacro{\tmp}{max(\value{z},\Z)}
  \setcounter{z}{\tmp}   
  \foreach \Xmax [count=\Y] in \Lst {
    \foreach \X in {1,...,\Xmax}   
     {\path (\X-1,-\Y,\Z) pic{unit cube};
     \pgfmathtruncatemacro{\tmp}{max(\value{x},\X)}
     \setcounter{x}{\tmp}
     \pgfmathtruncatemacro{\tmp}{max(\value{y},\Y)}
     \setcounter{y}{\tmp}
     }
    }
  }
 \begin{scope}[on background layer]
  \begin{scope}[canvas is xy plane at z=0,transform shape]
   \path[/tikz/3d cube/xy face]  (0,0) rectangle (\value{x},-\value{y});
   \draw[/tikz/3d cube/every face] (0,0) grid (\value{x},-\value{y});
  \end{scope}
  \begin{scope}[canvas is yz plane at x=0,transform shape]
   \path[/tikz/3d cube/yz face]  (0,0) rectangle (-\value{y},1+\value{z});
   \draw[/tikz/3d cube/every face] (0,0) grid (-\value{y},1+\value{z});
  \end{scope}
 \begin{scope}[canvas is zx plane at y=0,transform shape]
  \path[/tikz/3d cube/xz face]  (0,0) rectangle (1+\value{z},\value{x});
  \draw[/tikz/3d cube/every face] (0,0) grid (1+\value{z},\value{x});
 \end{scope}
 \end{scope}
}


\begin{document}
\tdplotsetmaincoords{70}{50} % the first argument cannot be larger than 90
\begin{tikzpicture}[line join=round,tdplot_main_coords]
 \begin{scope}[3d cube/.cd,every face/.style={},xy face/.style={fill=redxy},
    xz face/.style={fill=redxz},yz face/.style={fill=redyz}]
  \Planepartition{{6,6,5,4,4,4,2},{6,4,4,3,2,2},{5,4,3,3,2,1},{4,3,3,2,1},{4,2,2,1,1},{4,2,1},{2}}
 \end{scope}
\end{tikzpicture}
\end{document}