Deriving assembly directly contains all parts from derived assembly.
And all derived parts are added as fixed part. The intention is mostly
for user to customize visibilities of the derived parts as a way of
controling the level of details.
The SketchPlane expects the first element to be a planar face/edge to
define a work plane for any following draft wire/circle/arc elements.
The 2D constrainted elements can either be inside the defining
SketchPlane constraint, or other constrains following the SketchPlane
in the constraint group.
Add a new SketchPlane to define a new work plane for any following
draft elements. Add an empty SketchPlane to undefine the work plane,
effectively making any following draft elements free in 3D space.
* Draft wire points can be dragged individually.
* Draft wire individual edge can be moved and rotated.
* Draft circle/arc can be moved and rotated by dragging edge or face.
* Draft circle/arc radius can be changed by dragging vertex
* Draft arc first/last angle can be changed by dragging end points
