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True lofting is more than just sweeping curves through space to genreate
surfaces. The proper use of curves creates proper surfaces. Once the surface
has been generated, you need to go back and massage the surfaces to maintain
critical specifications such as:
- Check for Curvature Control
-
Check for Tangency Control
- Check for Dimensional Accuracy
-
Check for Patch Count
- Check for Polygon Arrangement
- Check for Correspondence Control
Parameterization
Curvature Control is controlling the radius
of each arc. Curve Analysis should result in a Bell Curve.
A negative radius is unacceptable for an
air foil as it indicates an inverse or dent.
Lofting Curve Analysis
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Lofting Curvature Control
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Tangency Control is the Angle between two
Surface Boundaries
The lack of tangency results in
surfaces that cannot be
concatenated or joined to an adjacent surface.
This leads to poor modeling practices
Good Lofting Tangency Control
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Bad Lofting Tangency Control
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Polygon arrangement is the placement
of control points on a patch.
Poor polygon arrangement results in:
-
-Increases patch count
- -Decreases dimensional accuracy
of the surface
- -Limits downstream use
- -Model is very susceptible to failure
(System Crash)
Good lofting polygon arrangement is key
Correspondence of points is the
alignment and organization of
adjacent patches.
Lack of correspondence control will create
a data explosion when surfaces are
concatenated
Good lofting correspondence points
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Bad lofting correspondence points
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Parameterization is the manual
control of polygonal alignment
and tangency of adjacent
patches.
Misaligned patches will cause
operations such as surface offsets
and fillets to fail.
Parameterization is required for downstream
usability.
Non-parameterized loft patches
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Non-parameterized loft patches
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Parameterized loft patches
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