On 9/2/2022 12:42 PM, andrew goh via Discuss wrote: > I'd guess unlike general computer graphics, 3d solid modelling has to > be solids. Hence, it is more complex than simply stitching surfaces > together. Yes and no.  Indeed, OpenSCAD does not natively stitch surfaces together.  It barely tolerates surfaces as a concept.  However, that doesn't mean that it can't be done.  BOSL2 does it. For historical reasons I don't use BOSL2 myself and so can't immediately give examples, but in my own work I have a "bez" function that accepts control points as arguments and returns a list of points along the curve.  I can then use concat() and other list manipulation tools to stitch them together into a single list of points, which I can then pass to polygon() to turn into a 2D object.  (And thence to linear_extrude() to turn into a 3D object.) I haven't done much with stitching Bézier surfaces together, but the BOSL2 documentation has some examples. See Example 2-4 under https://github.com/revarbat/BOSL2/wiki/beziers.scad#function-bezier_vnf .