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:

  • Curvature Control
  • Tangency Control
  • Dimensional Accuracy
  • Patch Count
  • Polygon Arrangement
  • 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

Lofting Curve Analysis

lofting curvature control

Lofting Curvature Control

 

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

Good Lofting Tangency Control

bad lofting tangency control

Bad Lofting Tangency Control

 

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

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

Good lofting correspondence points

bad lofting correspondence points

Bad lofting correspondence points

 

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

Non-parameterized loft patches

Non-parameterized loft patches

Non-parameterized loft patches

parameterized loft patches

Parameterized loft patches