Vfrdtyky

My quetion may be dumb, but consider that I am very new with Tikz.

I am trying to draw a tower similar to Eifel using the following code

documentclass{article}

usepackage{tikz}

usetikzlibrary{shapes.geometric}

usetikzlibrary{shapes.misc}



begin{document}



begin{tikzpicture}[{x=(1mm,0)},{y=(0,1mm)}]

deftowerwd{5}                 % tower width

deftowerht{10}                % tower height

deftowerar{4*towerwd/10}     % tower arc radius



deftower#1{% #1=position

    draw[thick]

        %... tower arc

        {#1++(-towerar,0)}

            arc(180:0:towerar)--

            (towerwd/2,0) to[out=120,in=270]

            (0,towerht) to[out=270,in=60]

            (-towerwd/2,0)--

            cycle

        ;

    }



tower{(0,0)} % this works!

tower{(0,20)} % this is messy!

end{tikzpicture}



end{document}

It works fine when I do tower{(0,0)}, but becomes messy when I use any other coordinate. What am I doing wrong here?

It becomes messy because ++ does not add these coordinates, you might use calc for that if there was not a (IMHO) much more elegant way: pics.

What do pics do? A pic is, as its name suggests, a small picture like your tower. pics can be placed and transformed. All I did was to move your tower code inside the definition of a pic by saying

 tikzset{pics/.cd,

    tower/.style={code={

        draw[thick]

            (-towerar,0)

                arc(180:0:towerar)--

                (towerwd/2,0) to[out=120,in=270]

                (0,towerht) to[out=270,in=60]

                (-towerwd/2,0)--

                cycle

            ;

    }}}

Here, the .cd switches to the pics subdirectory of pgfkeys tikz directory. The rest is just to teach TikZ the tower code.

documentclass{article}

usepackage{tikz}



begin{document}

tikzset{pics/.cd,

tower/.style={code={

    draw[thick]

        (-towerar,0)

            arc(180:0:towerar)--

            (towerwd/2,0) to[out=120,in=270]

            (0,towerht) to[out=270,in=60]

            (-towerwd/2,0)--

            cycle

        ;

}}}



begin{tikzpicture}[{x=(1mm,0)},{y=(0,1mm)}]

deftowerwd{5}                 % tower width

deftowerht{10}                % tower height

deftowerar{4*towerwd/10}     % tower arc radius

path (0,0) pic{tower} (0,20) pic{tower};

end{tikzpicture}



end{document}

But this example does not at all explain why people are excited about pics. Rather, you might want to add parameters instead of the somewhat clumsy deftowerwd{5} and so on statements. And you may want to change parameters from "outside". All this can be done with pics.

documentclass{article}

usepackage{tikz}



begin{document}

tikzset{pics/.cd,

tower/.style args={#1 wide and #2 high}{code={

    draw[thick]

        (-4*#1/10,0)

            arc(180:0:4*#1/10)--

            (#1/2,0) to[out=120,in=270]

            (0,#2) to[out=270,in=60]

            (-#1/2,0)--

            cycle

        ;

}}}



begin{tikzpicture}[{x=(1mm,0)},{y=(0,1mm)}]

path (0,0) pic{tower=5 wide and 15 high}

node[below]{Paris} (20,2) pic[rotate=-30,blue]{tower=5 wide and 10 high}

node[below]{Pisa};

end{tikzpicture}



end{document}