I would like to draw an octahedral diagram in my paper; I would prefer to present it as the 'upper hat' + the 'lower hat' (as it is common in the texts on triangulated categories). Could anyone tell me where I can find this diagram (certainly, the 'upper hat part' is sufficient) written down in latex. Maybe, someone could just share with me his own latex realization of this diagram (so that I could replace the original names of objects and morphisms by the ones I need)?

Mikhail, Here's an upper cap in xypic \xymatrix{ X'\ar[rd]^{[1]}\ar[dd]^{[1]} & & Z\ar[ll] \\ & Y\ar[ru]\ar[ld] & \\ Z'\ar[rr]^{[1]} & & X\ar[lu]\ar[uu] } at least it's enough of one to get you started. Note that I didn't construct it by hand. I have a script for building these kinds of diagrams visually: http://www.math.purdue.edu/~dvb/scripts/arraymaker If it's useful to you, help yourself. 


I think that this is an easy exercise in xypic. The exact diagram you want may not be in this user's guide, but the basics of xypic are easy enough that you should be able to create what you want. 


The same example given in xypic done in Tikz: More examples and code are at http://www.texample.net/tikz/examples/ and the manual http://mirror.ctan.org/graphics/pgf/base/doc/generic/pgf/pgfmanual.pdf
Changed from an octagon. 

