As pointed out in Issue #0004353 the OpenSCAD Workbench does not
correctly implement the angle parameter to rotate_extrude (it's a
relatively recent addition to OpenSCAD), nor does it attempt to do
anything with a specified $fn. This commit adds both features. To add
$fn handling, the code from the cylinder extrusion was mimicked,
allowing FreeCAD to create perfect, smooth representations when $fn
exceeds a user specified value in Preferences, but attempting to create
OpenSCAD's more discrete representation when using a lower $fn. Note
that this determination is made at creation time: if the user later
increases the segments parameter in the new object, it will remain
prismatic regardless of how high the value is made.
Modify the auxiliary spine to be a true helix, resulting in a much
smoother linear extrusion when a twist angle is applied. This also
corrects a bug in the scaling during linear extrusion, where non-uniform
scaling was not handled correctly.
The original implementation of the surface() function used a simple
B-spline representation for the surface, which generated degenerate
surface with several of OpenSCAD's demo input files. This commit
modifies the algorithm to generate a discrete surface identical to the
one generated within OpenSCAD itself. It also adds several units tests
to identify future regressions.
Note that PNG input is not yet supported for the surface() function.
The OpenSCAD module did not have any unit tests. This commit adds the
basic framework (and two very simple tests). The framework is modeled
after the unit tests in the FEM module.
