# Decorate pgfplots mesh

In my quest to solve this question I'm trying to see if I can decorate a mesh-plot by drawing many circles or maybe rectangles with a radius determined by \pgfplotspointmetatransformed. But I can't seem to decorate a mesh-plot. The MWE below contains three tries, all commented out, because all fail with ! Package PGF Error: I cannot decorate an empty path.. I'm using pgfplots 2011/12/29 v1.5.1 (git show 1.5.1-4-g53e640f ) and tikz 2010/10/13 v2.10 (rcs-revision 1.76).

\documentclass{standalone}
\usepackage{tikz}
\usepackage{pgfplots}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{decorations.shapes}
\pgfplotsset{compat=1.5}%
\begin{document}%
\begin{tikzpicture}
\begin{axis}
% all three attemps fail with:
% ! Package PGF Error: I cannot decorate an empty path.

I'm not exactly sure how this is going to solve the problem of the joins in your other question: The size of the circles would still change discretely, so wouldn't the result still be the same as when using line cap=round with straight line segments. –  Jake May 31 '12 at 10:22
Yes, that's right, but then the joins would end up looking like the second example in my answer, with line cap=rect. You'd need to do something like find half the angle between two consecutive line segments. The problem is related to TikZ: changing colour of a path half way along. –  Jake May 31 '12 at 12:24