How can I draw the Minkowski sum of two sets? [duplicate]

I would like to represent the ɛ-neighborhood of a convex polygon, which is the Minkowski sum of the polygon and a disk of radius ɛ. The polygon is given by its vertices, from which of course I could calculate a drawing, but I hope that there is a simpler solution using TikZ (though I'm equally happy with any other solution). Here is an example, the ɛ-neighborhood of a triangle.

• What have you got so far? If you give us the code for the non-simple solution, probably somebody can help produce the simpler. Right now, this is a do-it-for-me-after-working-out-what-it-I-want-done. – cfr Jun 23 '16 at 2:28
• @cfr: If I had the code of the non-simple solution, why would I bother to get a code for a simple solution? I don't want anyone to "do-it-for-me", I want someone to tell me how to do it. I'm sorry if the "what-I-want-done" part is not clear, I've tried to update it now. – domotorp Jun 23 '16 at 2:37
• Look at this: tex.stackexchange.com/a/129854/10898 – azetina Jun 23 '16 at 6:03
• @azetina: I don't want an svg, I've only linked to it so that people can see what kind of image I would like. – domotorp Jun 23 '16 at 6:30
• This not so difficult. You need (1) select the program, in which you like to draw (pstrick, tikz,...), then (2) search here or in texample.net for similar drawings and (3) start to draw. When you stuck with it, ask here, how to solve your particular problem. Otherwise, see @cfr comment. – Zarko Jun 23 '16 at 6:36

A starting point :

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

\begin{document}
\begin{tikzpicture}
\coordinate (a) at (0,0);
\coordinate (b) at (3,-1);
\coordinate (c) at (2,2);
\foreach \nd in {a, b, c} {\draw (\nd) circle (\radius);}
\draw ($(a)!\radius!-90:(b)$) -- ($(b)!\radius!90:(a)$) ($(b)!\radius!-90:(c)$) -- ($(c)!\radius!90:(b)$) ($(c)!\radius!-90:(a)$) -- ($(a)!\radius!90:(c)$) ($(a)!\radius!-90:(b)$);
\draw[dashed] (a) -- (b) -- (c) -- cycle;
\end{tikzpicture}

\end{document}