import geometry;

size(7cm,0);

path chemin=(0,0){dir(45)}..(1,0)..(1,.5)..(1.5,1)..(0,1)..cycle;

pen   stylo1=red, stylo2=blue;
point p1=(0,0),   p2=(1,1);
segment seg=segment(p1,p2);
line d2=perpendicular(p1,seg), d3=perpendicular(p2,seg);

axialshade(chemin,stylo1,p1,stylo2,p2);

draw(chemin);
dot(chemin);

draw(d2^^d3,1bp+dashed);
distance("D\'egrad\'e axial",p1,p2,dashed,Arrows);