convexity

An optional value, which can help OpenSCAD render shapes correctly in preview mode. The stated convexity make NO DIFFERENCE to the final rendering. If the convexity is set to low (or set to null), then the preview mode may not display correctly. A large convexity may cause the OpenSCAD to update slowly / suboptimally. See OpenSCAD documentation for the definition of convexity.

If shape2d is concave, set the convexity so that OpenSCAD's preview mode renders correctly.