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Two section curves:
Menu access: Shape | Other shapes | Swept
Description:
A two-section curves shape is defined as a surface swept by a curve named "mixed section curve" moving along two other curves named "guide curves".
Principle:
The mixed section curve is obtained by mixing the curves named section curves, which can be closed or open, not necessarily planar and can have angular points.
Each section curve has got a hooking point on each guide curve corresponding to the point where the mixed section curve is strictly equal to the section curve.
Between two hooking points, the mixed section curve is equal to a mix of the two section curves following an evolution law which can be linear or not.
General philosophy:
Select the TWO GUIDE CURVES option.
Select the first guide curve and set its direction.
Select the second guide curve and set its direction.
Select the section curves, select their directions and hooking points on each guide curve or select on the POSITION SECTION CURVE button (cf. positioning).
Optional point(s):
The
AUTOMATIC
button
allows to automatically select all the curves that intersect the guide
curve in order to use them as section curves.
Positioning:
In order to define exactly the sweeping movement, the simplest way consists in considering the section curve fixed in the coordinate system of which its origin move along the first guide curve, with the X axis oriented towards a point of the second guide curve and the Y axis is orthogonal to X and to the tangent of the first guide curve.
This coordinate system is called "sweeping coordinate system".
The section curves are usually defined in place; id est. their positions are the ones corresponding to the sweeping coordinate system with the hooking point as origin.
Nevertheless, it is also possible to choose the section curve from another coordinate system by pressing the POSITION SECTION CURVE button. In that case, the section curve will automatically be positioned in the sweeping coordinate system of the corresponding hooking point before starting the sweeping.
Deformation:
Deformation= AFFINITY or SCALING
The mixed section curve is deformed during the sweeping in order to keep the hooking points in contact with the guide sections.
Two kind of deformation are available:
The SCALING , which allow keeping the shape of the mixed section curve.
The AFFINITY deformation draw the mixed section curve out on X-axis of the sweeping coordinate system and does not change the Y dimension.
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Scaling |
Affinity |
Intermediate
sections generation:
MAKE SECTION
The swept shape calculation is made using two steps: intermediate sections calculation, then creation of the template shape on these sections.
It is possible to generate intermediate sections when creating a swept or later with the "Modify" function.
This functionality is very useful on two cases:
The swept failed, usually due to an auto-intersection area: the generation of the sections allows you to visualize the problem spot.
The swept doesn't give the expected result: it is advisable to generate intermediate sections, modify the unsatisfactory ones and create a loft shape.
The list 
allows you
to choose the correspondence between the curves
The option 
allows
you to choose the type of synchronization
between the curves.
The option Curves=
VISIBLE or
HIDDEN
allows
you to keep visible or not the curves after the ruled shape is created.
When curves are closed, you can choose
the type of shape to create with the option Type=
SOLID or
SURFACE
TYPE . When you choose the solid type, the section curves must
be closed.
The list 
allows you
to choose the mixing of the section curves.
Specific point(s):
The
guide curves can be open or closed, not necessarily planar, but
they must be tangentially continuous
(no angular point).
The
section curves can be open or closed, not necessarily planar and
can have angular points.
If the guide
curves are closed, you must select a minimum
of 4 section curves.
The resulting swept surface
must not have auto-intersection area.
