# How can I draw a 3-simplex diagram? [duplicate] But the direction of the arrows will be upward.(except for 1 ⟶ 0)

• Welcome to TeX.sx! I'd like to point you to this article for information on how to ask questions here. In particular, please show what sort of work you've done towards solving this problem. – A Gold Man Nov 26 '17 at 19:33
• tex.stackexchange.com/questions/57269/… should get you started. – Torbjørn T. Nov 26 '17 at 20:19
• May not be a duplicate. If this is just a commutative diagram then I agree with @Cragfelt but if OP wants a 3-simplex for (as an example) describing elementary homology calculations, then this is a different question. – Sandy G Dec 17 '17 at 4:24

It's very easy with tikz-cd: to have upwards arrows, just use u option.

\documentclass{article}
\usepackage{tikz-cd}
\tikzcdset{arrow style=tikz, diagrams={>=Stealth}}

\begin{document}
\begin{tikzcd}
& 3 \$2.5ex] & 2 \ar[u] \\[1ex] 1 \ar[rr] \ar[ru] \ar[ruu] && 0 \ar[lu] \ar[luu] \end{tikzcd} \end{document} Another possibility is to make a diagram that looks like a true 3-simplex. Of course you can adjust colors, arrowheads, line thickness, opacity, etc. as you see fit. Here is the code: \documentclass{article} \usepackage{tikz} \usetikzlibrary{decorations.markings} \begin{document} \begin{tikzpicture}[line join = round, line cap = round] \coordinate [label=above:3] (3) at (0,{sqrt(2)},0); \coordinate [label=left:2] (2) at ({-.5*sqrt(3)},0,-.5); \coordinate [label=below:1] (1) at (0,0,1); \coordinate [label=right:0] (0) at ({.5*sqrt(3)},0,-.5); \begin{scope}[decoration={markings,mark=at position 0.5 with {\arrow{to}}}] \draw[densely dotted,postaction={decorate}] (0)--(2); \draw[fill=lightgray,fill opacity=.5] (1)--(0)--(3)--cycle; \draw[fill=gray,fill opacity=.5] (2)--(1)--(3)--cycle; \draw[postaction={decorate}] (1)--(0); \draw[postaction={decorate}] (1)--(2); \draw[postaction={decorate}] (2)--(3); \draw[postaction={decorate}] (1)--(3); \draw[postaction={decorate}] (0)--(3); \end{scope} \end{tikzpicture} \end{document}  xy solution. \documentclass{report} \usepackage[all]{xy} \begin{document} \[ \xymatrix{ & 3 \\ & 2 \ar[u] \\ 1 \ar[rr] \ar[ru] \ar[ruu] && 0 \ar[lu] \ar[luu] }$
\end{document}


A solution with plain TikZ. The outer triangle is equilateral.

\documentclass[tikz]{standalone}
\begin{document}
\begin{tikzpicture}
\path[->]
node (2) {2}
+(0, 1) node (3) {3}
+(-30:1) node (0) {0}
+(210:1) node (1) {1}
(1) edge (0)
(0) edge (2)
(0) edge (3)
(1) edge (2)
(1) edge (3)
(2) edge (3)
;
\end{tikzpicture}
\end{document} With different arrow heads, for example:

\documentclass[tikz]{standalone}
\usetikzlibrary{arrows.meta}
\begin{document}
\begin{tikzpicture}
\path[->, >={Computer Modern Rightarrow[length=3pt, width=3pt]}]
node (2) {2}
+(0, 1) node (3) {3}
+(-30:1) node (0) {0}
+(210:1) node (1) {1}
(1) edge (0)
(0) edge (2)
(0) edge (3)
(1) edge (2)
(1) edge (3)
(2) edge (3)
;
\end{tikzpicture}
\end{document} 