|
Lofting interpolates a surface through a given set of curves. The curves provide the
u parameter of the resulting surface. The
v parameter is computed and generated by the lofting algorithm. This technique allows the formation of relatively complex surfaces from a set of cross sectional curves. Lofting has been widely used for decades in the shipbuilding, automotive, and aircraft industries.
|
|
|
Lofting controls how the surface will pass through the set of input curves by controlling the magnitudes and directions of the tangent vectors going into and out of each curve. These tangents are controlled by coedge surface tangents or laws. Figure 1-1 shows an example of lofting five wires (w0-w4) with wire w0 and w4 having tangent constraints.
|
|
|
ACIS laws are supported in the lofting API and Scheme interfaces. A vector field can be specified using a law to control the take-off vector on any coedge in the profile of a loft surface. Lofting surfaces that do not contain a surface or a law can be simplified.
|
|
|
In general, lofting:
|
|
|
Supports surface creation between coedges of wires and surfaces
|
|
|
Controls the take-off vector weight factors for the loft transitions
|
|
|
Supports laws to define coedge tangency constraints
|
|
|
Supports surface isoparametric or arc length parameterization
|
|
|
Can align the direction of the cross section curves so that they are in the same direction as the first curve
|
|
|
Supports twist and non-twist minimization of the cross-section
|
|
|
Supports control of the take-off vector direction, perpendicular to the coedge or in the loft direction
|
|
|
Supports guide curves
|
|
|
Can simplify the created surface to an analytical surface (planar, conical, spherical, or toroidal), if applicable
|
|
|
Can create a closed or open solid body
|