advanced rendering for AutoCAD
I really don't know why arcs act like they were invisible, but you surely can convert arcs with thikness into meshes, without increasing significantly the file dimensions.
Roy: no, there are various alternatives, as Miguel pointed. It's just that one user missed it, more when the thickness-based extrusion of a line is rendered. It looked like a forgotten case.
another thing we miss is the spherical decals (currently, there are the box, and cilindrical ones). This is quite more important than the extruded arcs, at least to this particular user. (this is just feedback that you can use to sort the wish list).
to print a logo on a spherical surface, for example. As seen, this was possible on Accurender 4.