\documentclass{article}
%% compiler avec lualatex
\usepackage[margin=2.5cm]{geometry}
\usepackage{luamesh}
\usepackage{fontspec}
\usepackage{multido}
\pagestyle{empty}
\begin{document}

% \buildMesh[print=points,  meshpoint = I, color=red]{(0,0);(3.5,3);(7,0);(7.5,5);(1.61,3.14);(3,1);(6,1.5)}

% \buildMesh[tikz, bbox = show]{(0,0);(3.5,3);(7,0);(7.5,5);(1.61,3.14);(3,1);(6,1.5)}

% \buildMesh[mode=ext]{mesh.txt}

% \meshAddOnePoint[
% meshpoint = x,
% colorNew =green!20!red,
% colorBack=red!10,
% colorCircle = green!70,
% scale=0.6cm]
% {(0,0);(3.5,3);(7,0);(7.5,5);(1.61,3.14);(6,4)}{(3,1)}
% \meshAddOnePoint[
% meshpoint = x,
% colorBack=red!10,
% colorNew = green!20!red,
% scale=0.6cm,
% step=cavity]
% {(0,0);(3.5,3);(7,0);(7.5,5);(1.61,3.14);(6,4)}{(3,1)}
\meshAddOnePoint[
meshpoint = x,
colorBack=red!10,
colorNew = green!20!red,
scale=0.6cm,
step=badtriangles,
newpoint = y,
bbox = show
]
{(0,0);(3.5,3);(7,0);(7.5,5);(1.61,3.14);(6,4)}{(3,1)}

\mplibcolor\myclr{red}

\newcommand\test{draw (0,0) -- (2cm,0) withcolor \myclr;}

\begin{mplibcode}
  beginfig(0);
  %\meshAddOnePoint[picture=embedded]{(0,0);(3.5,3);(7,0);(7.5,5);(1.61,3.14);(6,4)}{(3,1)}
  \test
  endfig;
\end{mplibcode}


\end{document}
