In Mathematica 12, the line of code below plots a torus in Graphics3D[] using ResourceFunction[“Torus”]. It was plotted with Opacity[.2]. I was very surprised to see a sphere inscribed in the torus at approximately \phi = 3\pi/2 where \phi is the angle of the outer radius. I take it this is some artifact of the BSpline function used by the “Torus” resource. Is there a mathematical reason for it, and is there any way to get rid of the inner sphere?
It looks like ResourceFunction[“Torus”] is defined by creating a tube around a BSplineCurve. The default CapForm for Tube is “Round”. So, I believe that what you are seeing is the overlap of the end caps of the tube. FWIW, in version 13 Torus is a built-in function, so no need for the ResourceFunction.
