# Tikz: Draw lines between edges of rectangles

The following code

\documentclass[tikz,border=1mm]{standalone}
\usepackage{tikz}
\begin{document}
\newcommand{\opacity}{0.6}
\begin{tikzpicture}
\draw[xshift=1cm,fill=gray,draw=black,opacity=\opacity]
(0,0) -- (3,3) -- (3.2,3) -- (0.2,0) -- (0,0);
\draw[xshift=2cm,fill=gray,draw=black,opacity=\opacity]
(0,0) -- (2,2) -- (2.2,2) -- (0.2,0) -- (0,0);
\draw[xshift=3cm,fill=gray,draw=black,opacity=\opacity]
(0,0) -- (1,1) -- (1.2,1) -- (0.2,0) -- (0,0);
\end{tikzpicture}
\end{document}


produces the following output:

How can I connect the edges of the rectangles with a line? I don't want to use coordinates (\draw (0,0) -- (2,2)) but rather something like

\draw (rectangle1.north east) -- (rectangle2.north west).

It would also be great if there is a solution like:

\draw (A1)(0,0) -- (B1)(1,1) -- (C1)(1.2,1) -- (D1)(0.2,0) -- (E1)(0,0);
\draw (A2)(0,0) -- (B2)(1,1) -- (C2)(1.2,1) -- (D2)(0.2,0) -- (E2)(0,0);
\draw (A1) -- (C2)

• at drawed shapes this is not possible. they haven't defined names nor anchors. you can do this by use of coordinates for each shape corner, but this will cause quite complex code. for example for the first shape: \draw[myshape] (0,0) coordinate (A1) -- (3,3) coordinate (A2) -- (3.2,3) coordinate (A3) -- (0.2,0) coordinate (A4) -- cycle; and than draw for example draw (A1) -- (A3); – Zarko Dec 30 '18 at 19:27

Something like this ?

\documentclass[tikz,border=1mm]{standalone}
\usepackage{tikz}
\begin{document}
\newcommand{\opacity}{0.6}
\begin{tikzpicture}
\draw[xshift=1cm,fill=gray,draw=black,opacity=\opacity]
(0,0)coordinate(A1) -- (3,3)coordinate(A2) -- (3.2,3)coordinate(A3) -- (0.2,0) coordinate(A4) -- cycle;
\draw[xshift=2cm,fill=gray,draw=black,opacity=\opacity]
(0,0)coordinate(B1) -- (2,2)coordinate(B2) -- (2.2,2)coordinate(B3) -- (0.2,0)coordinate(B4) -- cycle;
\draw[xshift=3cm,fill=gray,draw=black,opacity=\opacity]
(0,0)coordinate(C1) -- (1,1) coordinate(C2)-- (1.2,1)coordinate(C3) -- (0.2,0)coordinate(C4) -- cycle;

\draw(A4)--(B1);
\draw(B4)--(C1);
\draw(A3)--(B3)--(C3);

\end{tikzpicture}
\end{document}


Update using a foreach loop:

\documentclass[tikz,border=1mm]{standalone}
\usepackage{tikz}
\begin{document}
\newcommand{\opacity}{0.6}
\begin{tikzpicture}

\foreach \xs/\p/\x in{1/A/3,2/B/2,3/C/1}
{\draw[xshift=\xs cm,fill=gray,draw=black,opacity=\opacity]
(0,0)coordinate(\p1)
--(\x,\x)coordinate(\p2)
--(\x+0.2,\x)coordinate(\p3)
--(0.2,0)coordinate(\p4)
--cycle;}

\draw(A4)--(B1);
\draw(B4)--(C1);
\draw(A3)--(B3)--(C3);

\end{tikzpicture}
\end{document}


• Great answer! Is it possible, that \draw(A-4)--(B-1); should be \draw(A4)--(B1);? The same probably also applies to the other cases. – Samuel Jan 3 at 8:40
• @Samuel Yes it is perfectly possible! Just replace coordinate(\p-1),...,coordinate(\p-4) with coordinate(\p1),...,coordinate(\p4) . I will update my answer soon. – Hafid Boukhoulda Jan 3 at 9:11

As far as I understand your post, if two coordinates are given, the full shape is fixed. Your shape is not a rectangle, but a trapezium, and there are predefined shapes available.

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{shapes.geometric}
\begin{document}
\begin{tikzpicture}[my trapez/.style={trapezium,%inner xsep=0pt,inner ysep=0pt,
trapezium left angle=135, trapezium right angle=45,rotate=45,
minimum width={#1*sqrt(2)*1cm},minimum height={sqrt(2)*1mm},draw,fill=gray,
trapezium stretches body,anchor=west}]
\node[my trapez=3]  (L)    at (1,0) {};
\node[my trapez=2]  (M)    at (2,0) {};
\node[my trapez=1]  (R)    at (3,0) {};
\draw ([xshift=-sqrt(2)*1mm]L.west) -- ([xshift=sqrt(2)*1mm]R.west);
\draw ([xshift=sqrt(2)*1mm]L.east) -- ([xshift=sqrt(2)*1mm]R.east);
\end{tikzpicture}
\end{document}


As you can see, there are two mild problems with this approach:

1. it is nontrivial to control the dimensions precisely, at least for this shape;
2. to specify the position precisely, you need to think a bit. (This is also the case in Zarko's otherwise nice answer.)

Therefore, I'd like to propose a different route, in which you to draw and fill the thing as a decoration, which also lets you name the coordinates.

\documentclass[tikz,border=1mm]{standalone}
\usetikzlibrary{decorations.pathreplacing}
\tikzset{trapez width/.initial=0.2cm,
my trapez/.style={decorate,decoration={
show path construction,
lineto code={\filldraw
(\tikzinputsegmentfirst) coordinate(#1-south west)
-- (\tikzinputsegmentlast) coordinate(#1-north west)
-- ([xshift=\pgfkeysvalueof{/tikz/trapez width}]\tikzinputsegmentlast)
coordinate(#1-north east)
-- ([xshift=\pgfkeysvalueof{/tikz/trapez width}]\tikzinputsegmentfirst)
coordinate(#1-south east) -- cycle;
}}}}

\begin{document}
\begin{tikzpicture}
\begin{scope}[fill=gray,opacity=0.6]
\draw[my trapez=L] (1,0) -- (4,3);
\draw[my trapez=M] (2,0) -- (4,2);
\draw[my trapez=R] (3,0) -- (4,1);
\end{scope}
\draw (L-north east) --  (R-north east)
(L-south west) --    (R-south east);
\end{tikzpicture}
\end{document}


Now you really only need to specify two coordinates, which will become precisely named coordinates.

let me elaborate my comment:

• for shapes, which you draw as you show in your mwe, this is not possible
• those shapes haven't defined names nor anchors.
• you can do this by use of coordinates for each shape corner, but this can result in quite complex code. for example for the first shape:

\draw[myshape] (0,0) coordinate (A1) --
(3,3) coordinate (A2) --
(3.2,3) coordinate (A3) --
(0.2,0) coordinate (A4) -- cycle;


and than draw for example

\draw (A1) -- (A3);

• a way to simplify this code extension can be use of the small pictures: \pic (for details about it see chapter 18 Pics: Small Pictures on Paths in Tikz & PGF manual, v 3.0.1a, page 251):

\documentclass[tikz,border=3mm]{standalone}

\begin{document}
\begin{tikzpicture}[
pics/myshape/.style = {code={ % definition of your shape
\draw[fill=gray,opacity=\opacity]
( 0.0,0) coordinate (-1) -- ++  % south west
( 0.2,0) coordinate (-2) -- ++  % south east
(#1,#1)  coordinate (-3) -- ++  % north east, coordinate is determined by parameter #1
(-0.2,0) coordinate (-4) --     % north west
cycle;}}
]
\def\opacity{0.6}
\pic (A) [above right] at (0,0) {myshape={3}}; % "3" is parameter which define size of shape
\pic (B) [above right] at (1,0) {myshape={2}};
\pic (C) [above right] at (2,0) {myshape={1}};
\draw[very thin, red, densely dashed]
(A-3) -- (B-3); % instead of \draw (rectangle1.north east) -- (rectangle2.north west).
\end{tikzpicture}
\end{document}

• for coordinates name you can select more meaningful names. for example instead of -1 may be more appropriate -sw, which can associate you on "south west", etc.