LaTeX source

\documentclass{amsart}
\usepackage{amsmath,amssymb,nopageno}
\usepackage[all]{xy}
\begin{document}
\begin{align*}
\underset{\text{\large(lower cap)}}{\xymatrix@=2em{
X' \ar[dddd] \ar[ddrr]_i^{[1]} & & & & Z \ar[llll] \\
& & d & & \\
& + & Y \ar[uurr]_v \ar[ddll]_j & + & \\
& & d & & \\
Z' \ar[rrrr]^{[1]} & & & & X \ar[uull]_u \ar[uuuu]_{v \circ u}
}}
&&
\underset{\text{\large(upper cap)}}{\xymatrix@=2em{
X' \ar[dddd]^{[1]} & & & & Z \ar[llll] \ar[ddll] \\
& & + & & \\
& d & Y' \ar[uull]^g \ar[ddrr]_{[1]} & d & \\
& & + & & \\
Z' \ar[uurr]^f \ar[rrrr] & & & & X \ar[uuuu]_{v \circ u}
}}
\end{align*}
\end{document}

Summary

DescriptionAxiom TR4 (caps).svg	A depiction of axiom TR4 of a triangulated category. The figure in File:Axiom TR4 (polyhedron).svg is rendered two-dimensionally as its upper and lower halves
Date	14 January 2009
Source	Own work (Original text: I created this work entirely by myself.)
Author	Ryan Reich
Other versions	File:Octahedral diagram variant.svg, File:Axiom TR4 (caps).svg
SVG development InfoField	The SVG code is valid.   This diagram was created with an unknown SVG tool.

Licensing

I, the copyright holder of this work, release this work into the public domain. This applies worldwide. In some countries this may not be legally possible; if so: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.