How to decorate only parts of a TikZ path - TeX

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How to decorate only parts of a TikZ path

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4 years ago samcarter

In the following example, I would like to decorate only the arc at the bottom of the shape with decorate,decoration=snake, the Bézier curves at the top of the shape should remain as they are.

I already tried:

shifting the decoration with pre length=60pt, but this converted the Bézier curves into straight lines
decomposing the shape into two parts, but then I face problems when only drawing the outlines or filling with a ballshade in orer to imitate a 3D look

\documentclass{standalone}
\usepackage{tikzlings}
\usetikzlibrary{decorations.pathmorphing}

\begin{document}
	
\begin{tikzpicture}[scale=3]
\fill 
( -0.39, 1.40) 
.. controls (-0.32, 1.58) and (-0.32, 2.09) .. ( 0.00, 2.09) 
.. controls ( 0.32, 2.09) and ( 0.32, 1.58) .. ( 0.39, 1.40) 
arc [start angle=-60,end angle=-120,radius=0.77] 
-- cycle;
\end{tikzpicture}	
	
\end{document}

xxxxxxxxxx
 
\documentclass{standalone}\usepackage{tikzlings}\usetikzlibrary{decorations.pathmorphing}​\begin{document}    \begin{tikzpicture}[scale=3]\fill ( -0.39, 1.40) .. controls (-0.32, 1.58) and (-0.32, 2.09) .. ( 0.00, 2.09) .. controls ( 0.32, 2.09) and ( 0.32, 1.58) .. ( 0.39, 1.40) arc [start angle=-60,end angle=-120,radius=0.77] -- cycle;\end{tikzpicture}       \end{document}
show all 16 lines

Top Answer

4 years ago user 3.14159

Uii, a black ghost. 😸. You can just use decorate inside a path to decorate certain seqments.

\documentclass{standalone}
\usepackage{tikzlings}
\usetikzlibrary{decorations.pathmorphing}

\begin{document}
	
\begin{tikzpicture}[scale=3]
\fill[decoration=snake] 
( -0.39, 1.40) 
.. controls (-0.32, 1.58) and (-0.32, 2.09) .. ( 0.00, 2.09) 
.. controls ( 0.32, 2.09) and ( 0.32, 1.58) .. ( 0.39, 1.40) 
decorate {arc [start angle=-60,end angle=-120,radius=0.77]}
-- cycle;
\end{tikzpicture}	
	
\end{document}

xxxxxxxxxx
 
\documentclass{standalone}\usepackage{tikzlings}\usetikzlibrary{decorations.pathmorphing}​\begin{document}    \begin{tikzpicture}[scale=3]\fill[decoration=snake] ( -0.39, 1.40) .. controls (-0.32, 1.58) and (-0.32, 2.09) .. ( 0.00, 2.09) .. controls ( 0.32, 2.09) and ( 0.32, 1.58) .. ( 0.39, 1.40) decorate {arc [start angle=-60,end angle=-120,radius=0.77]}-- cycle;\end{tikzpicture}       \end{document}
show all 16 lines

BTW, pre length also works, you only need to add pre=curevto. (In this very case this is not what you want to do, I think, because you would have to tune the pre length by hand, which I did not do.)

\documentclass{standalone}
\usepackage{tikzlings}
\usetikzlibrary{decorations.pathmorphing}

\begin{document}
	
\begin{tikzpicture}[scale=3]
\fill[decorate,decoration={snake,pre length=145pt,pre=curveto}] 
( -0.39, 1.40) 
.. controls (-0.32, 1.58) and (-0.32, 2.09) .. ( 0.00, 2.09) 
.. controls ( 0.32, 2.09) and ( 0.32, 1.58) .. ( 0.39, 1.40) 
arc [start angle=-60,end angle=-120,radius=0.77] 
-- cycle;
\end{tikzpicture}	
	
\end{document}

xxxxxxxxxx
 
\documentclass{standalone}\usepackage{tikzlings}\usetikzlibrary{decorations.pathmorphing}​\begin{document}    \begin{tikzpicture}[scale=3]\fill[decorate,decoration={snake,pre length=145pt,pre=curveto}] ( -0.39, 1.40) .. controls (-0.32, 1.58) and (-0.32, 2.09) .. ( 0.00, 2.09) .. controls ( 0.32, 2.09) and ( 0.32, 1.58) .. ( 0.39, 1.40) arc [start angle=-60,end angle=-120,radius=0.77] -- cycle;\end{tikzpicture}       \end{document}
show all 16 lines

1 Answer