[Tex/LaTex] Tikz: Lining up input and output nodes in multiple input multiple output diagram

nodestikz-pgf

I am attempting to draw a multiple input multiple output style diagram, using code that uses the following structure:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\usetikzlibrary{positioning}


\begin{document}

\begin{tikzpicture}
\tikzset{packet/.style={rectangle, draw, very thick, minimum size=8mm, rounded corners=1mm, fill=blue!50!white!30}}
\tikzset{mixing/.style={rectangle, draw, very thick, minimum width=35ex, rounded corners=1mm, fill=red!70!orange!30,rotate=90}}

\node[packet] (A) at (0,0) {Node A};
\node[packet] (B) [right=2cm of A] {Node B};
\node[mixing] (pro) at ($(A) !.5! (B) + (0.0,-1.0)$) {Multiple Input Multiple Output process};

\node[packet] (C) at (0.0,-2.1) {Node C};
\node[packet] (D) [right=2cm of C] {Node D};

\draw[->] (A.east) -- (B.west);
\draw[->] (C.east) -- (D.west);
\end{tikzpicture}
\end{document}

which produces the following diagram:
enter image description here

What I'd like to know is how to draw the arrows so that the 'Multiple Input Multiple Output process' bisects the line so that it is split into two parts, so there one arrow going into the process on the left (from node A for example) and one going out on the right (for example to node B).

I am aware of the notation which set the entry/exit of a line into a node (something like name_of_node.180, where the 180 specifies the angle of entry/exit to the node relative to the centre of the node), for example here Block Diagrams Multi Input – Multi Output Components in TikZ

However is it possible to force the entry and exit points of the arrows of the 'process' node to be 'level' with a pair of nodes (A and B, or C and D). (Effectively in the diagram below it's as if the process node bisects the arrows, splitting them into two, as mentioned previously).

Best Answer

You can use the perpendicular coordinate system:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\usetikzlibrary{positioning}


\begin{document}

\begin{tikzpicture}
\tikzset{packet/.style={rectangle, draw, very thick, minimum size=8mm, rounded corners=1mm, fill=blue!50!white!30}}
\tikzset{mixing/.style={rectangle, draw, very thick, minimum width=35ex, rounded corners=1mm, fill=red!70!orange!30,rotate=90}}

\node[packet] (A) at (0,0) {Node A};
\node[packet] (B) [right=2cm of A] {Node B};
\node[mixing] (pro) at ($(A) !.5! (B) + (0.0,-1.0)$) 
  (mult) {Multiple Input Multiple Output process};

\node[packet] (C) at (0.0,-2.1) {Node C};
\node[packet] (D) [right=2cm of C] {Node D};

\draw[->] (A.east) -- (mult.north|-A.east);
\draw[->] (mult.south|-A.east) -- (B.west);
\draw[->] (C.east) -- (mult.north|-C.east);
\draw[->] (mult.south|-C.east) -- (D.west);
\end{tikzpicture}
\end{document}

enter image description here

A better alternative is to use:

\draw[->] (A.east) -- (mult.north|-A.east);
\draw[->] (mult.south|-A.east) -- (B.west|-A.east);
\draw[->] (C.east) -- (mult.north|-C.east);
\draw[->] (mult.south|-C.east) -- (D.west|-C.east);

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!

In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
  reversed ellipse/.style={
    ellipse,
    reverse the ellipse%
  },
  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
  }
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,0) {hello world};

\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,-2) {hello world};
\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

[Tex/LaTex] How to define the default vertical distance between nodes

I don't really get the question so I hope this is what you wanted. If you include a full document (such that we copy paste and see the problem on our systems) things are much more easier.

Here, you can change the default setting within a scope but your block style had a node distance which was resetting every time it is issued. I've made it 2mm such that we can see the difference easier.

\documentclass[tikz]{standalone}
\usetikzlibrary{arrows,shapes.geometric,positioning}

\begin{document}
\begin{tikzpicture}[decision/.style={diamond, draw, text width=4.5em, text badly centered, node distance=3.5cm, inner sep=0pt},
                    block/.style   ={rectangle, draw, text width=6em, text centered, rounded corners, minimum height=4em, minimum height=2em},
                    cloud/.style   ={draw, ellipse, minimum height=2em},
                    line/.style    ={draw,-latex'},
                    node distance = 1cm, 
                    auto]
    \node [block] (1st) {1st};
    \node [block, right= of 1st]  (2nd1) {2nd1};
\begin{scope}[node distance=2mm and 10mm]%Here we change it for everything inside this scope
    \node [block, above= of 2nd1] (2nd2) {2nd2};
    \node [block, below= of 2nd1] (2nd3) {2nd3};
    \node [block, right= of 2nd1] (3rd1) {3rd1};
    \node [block, above= of 3rd1] (3rd2) {3rd2};
    \node [block, above= of 3rd2] (3rd3) {3rd3};
\end{scope}
    \node [block, below= of 3rd1] (3rd4) {3rd4};
    \node [block, below= of 3rd4] (3rd5) {3rd5};

    \path [line] (1st) -- (2nd1);
    \path [line] (2nd1) -- (2nd2);
    \path [line] (2nd1) -- (2nd3);
    \path [line] (2nd2) -- (3rd3);
    \path [line] (2nd1) -- (3rd1);
    \path [line] (1st) -- (2nd1);
\end{tikzpicture}
\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

[Tex/LaTex] How to define the default vertical distance between nodes

Related Question