[Tex/LaTex] Ugly sharp edges when using `rounded corners` in TikZ

tikz-pgf

The following picture produces ugly sharp edges

\documentclass[11pt]{scrartcl}
\usepackage{tikz}
\begin{document}
\begin{center}
\begin{tikzpicture}
\draw[fill=black]
    (-2,1) circle (2pt) node  (tl) {} 
    (0,1) circle (2pt) node  (tc) {} 
    (2,1) circle (2pt) node  (tr) {} 
    (-6,0) circle (2pt) node  (ll) {} 
    (-4,0) circle (2pt) node  (l) {} 
    (4,0) circle (2pt) node  (r) {}
    (6,0) circle (2pt) node  (rr) {};
\draw[draw=orange, fill=orange]
    (-2,-1) circle (2pt) node  (bl) {} 
    (0,-1) circle (2pt) node  (bc) {} 
    (2,-1) circle (2pt) node  (br) {};
\draw[>=latex, ->, thick]
    (l) edge (tl)
    (r) edge (tr);
\draw[>=latex, ->,thin, orange]
    (bl) edge (l)
    (br) edge (r);
\draw[>=latex, <->, thick]
    (ll) edge (l)
    (rr) edge (r)
    (tl) edge (tc)
    (tc) edge (tr);
\draw[>=latex, <->, orange]
    (bl) edge (bc)
    (bc) edge (br);
\path[rounded corners=1cm, draw=gray!70]
    (-1-6,1) -- (2-6,1) -- (4-6,2) -- (8-6,2) --
    (10-6,1) -- (13-6,1) --(13-6,-1) -- (10-6,-1) --
    (8-6,0) -- (4-6,0) -- (2-6,-1) -- (-1-6,-1) -- cycle;
\path[rounded corners=1.5cm, draw=gray!50]
    (-1-6-0.5,1+0.5) -- (2-6,1+0.5) -- (4-6,2+0.5) --
    (8-6,2+0.5) -- (10-6,1+0.5) -- (13-6+0.5,1+0.5) --
    (13-6+0.5,-1-0.5) -- (10-6,-1-0.5) -- (8-6,-2-0.5) --
    (4-6,-2-0.5) -- (2-6,-1-0.5) -- (-1-6-0.5,-1-0.5) -- cycle;
\end{tikzpicture}
\end{center}
\end{document}

Apparantly, rounded corners first calculates the rounded corners, and then joins the endpoints with a straight line segment. the problem disappears if I set rounded corners=1cm for the second curve.

How can I get larder rounded corners without the jagged edges?

enter image description here

Best Answer

1cm is also too big and visible if you zoom enough. But for a limited number of operations(mostly path morphing operations), you can temporarily change the settings as you go by putting thinggs inside a brace pair and giving options to that. 

\documentclass[tikz]{standalone}
\begin{document}
\begin{tikzpicture}
\path[rounded corners=1.5cm, draw=gray!50]
    (-1-6-0.5,1+0.5) -- (2-6,1+0.5) {[rounded corners=0.5cm]-- (4-6,2+0.5)} --
    (8-6,2+0.5) {[rounded corners=0.1cm]-- (10-6,1+0.5)} -- (13-6+0.5,1+0.5) --
    (13-6+0.5,-1-0.5) -- (10-6,-1-0.5) {[rounded corners=0.8cm]--(8-6,-2-0.5)} --
    (4-6,-2-0.5) {[rounded corners=0.8cm]--(2-6,-1-0.5)} --(-1-6-0.5,-1-0.5)-- cycle;
\end{tikzpicture}
\end{document}

enter image description here

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