Help:Fancy diagram

The Diagram from $\rm The\ \TeX{}Book$, p. 182:

$$ \def\normalbaselines{\baselineskip20pt\lineskip1pt\lineskiplimit0pt } \def\noalign{} \def\vskip#1pt{} \def\hidewidth{} \def\mapright#1{\smash{ \mathop{\longrightarrow}\limits^{#1}}} \def\mapdown#1{\Big\downarrow \rlap{\vcenter{\hbox{$\scriptstyle#1$}}}} \matrix{\noalign{\vskip6pt}&&&&&&0\cr &&&&&&\mapdown{}\cr 0&\mapright{}&{\cal O}_C&\mapright\iota& \cal E&\mapright\rho&\cal L&\mapright{}&0\cr &&\Big\Vert&&\mapdown\phi&&\mapdown\psi\cr 0&\mapright{}&{\cal O}_C&\mapright{}& \pi_*{\cal O}_D&\mapright\delta& R^1f_*{\cal O}_V(-D)&\mapright{}&0\cr &&&&&&\mapdown{\theta_i\otimes\gamma^{-1}}\cr &&&&&&\hidewidth R^1f_*\bigl({\cal O} _V(-iM)\bigr)\otimes\gamma^{-1}\hidewidth\cr &&&&&&\mapdown{}\cr &&&&&&0\cr\noalign{\vskip6pt}} $$

Here is the $\rm \TeX$ code, as used in Knuth's book, to show the mathjax compatibility with plain $\rm \TeX$.

(For a $\rm \LaTeX$- encoding see here.)

<pre> \def\normalbaselines{\baselineskip20pt\lineskip1pt\lineskiplimit0pt } \def\noalign{} \def\vskip#1pt{} \def\hidewidth{} \def\mapright#1{\smash{ \mathop{\longrightarrow}\limits^{#1}}} \def\mapdown#1{\Big\downarrow \rlap{\vcenter{\hbox{$\$$\scriptstyle$\#1\$$}}}} \matrix{\noalign{\vskip6pt}&&&&&&0\cr &&&&&&\mapdown{}\cr 0&\mapright{}&{\cal O}_C&\mapright\iota& \cal E&\mapright\rho&\cal L&\mapright{}&0\cr &&\Big\Vert&&\mapdown\phi&&\mapdown\psi\cr 0&\mapright{}&{\cal O}_C&\mapright{}& \pi_*{\cal O}_D&\mapright\delta& R^1f_*{\cal O}_V(-D)&\mapright{}&0\cr &&&&&&\mapdown{\theta_i\otimes\gamma^{-1}}\cr &&&&&&\hidewidth R^1f_*\bigl({\cal O} _V(-iM)\bigr)\otimes\gamma^{-1}\hidewidth\cr &&&&&&\mapdown{}\cr &&&&&&0\cr\noalign{\vskip6pt}} </pre>