no linewidth with parametric plot

edit

parametric_plot takes an argument thickness as follows:

sage: parametric_plot([cos(x),sin(x)],x,0,2*pi,thickness=5)

(2019 additional answer to this 2011 question)

Note that the Three.js viewer does not respect thickness on Windows and some macOS.

Instead, use radius to create a cylinder around the curve. See:

• https://trac.sagemath.org/ticket/26410

We tried to be consistent in that "thickness" specifies a width that does not change as you zoom in and out, while linewidth does visually change as you zoom in and out. If that is not the case, it should be fixed.