Curvature continuous blends are the new age replacement for lead-in + fillet construction of the traditional world. While lot of CAD packages have G2/G3 continuous fillet capabilities there are some critical points to be addressed before successfully using such blends.

At one point in time Alias used to run only on SGI workstation and IRIX OS. Slowly over time it was ported to many different hardware/OS, like IBM/AIX, HP/HPUX, SUN/Solaris. During that time the hardware was expensive and limited. But neverthless, the stability of Alias on IRIX was remarkable. Finally with V10 it was ported to PC and recently to Mac.

Many people tend to use trim edges to create surfaces. However, by using so the resultant surfaces may become heavy or may contain multi-knots. The Curve Edit > Fit Curve function can be used to create quality curves. But the fit curve (till v 2010) function only operates on cross-section data.

The layer bar (and the object lister and the layer stats) shows the layer information. The layers can be arranged visually by click drag MMB either to left and right. Additionally the layers can be grouped together to form categories. Default categories are All layers, Reference and Selected Layers. Additional Categories can be made by clicking on the categories and choosing editor.

Categories are very useful in cases where large number of layers are present. By selecting the categories, only the layers in that category are visible. It is analogous to layer groups in other CAD packages.

 

 

 

 


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Alias uses two different types of parameters for knot spacing; Uniform and chord length. It is best to use either of the two. Using both types of curves together to create surfaces might create cross knot insertions or multiple knots. Uniform parameter is better if you want better explicit control of the geometry. It also allows detaching geometry in a predictable manner.
For a multiple span curve/surface, chord length based parameter gives better internal continuity as well as better texture layout. By default curve creation using edit points (including Blend curves) defaults to chord length based knot parameter and curve creation using CVs defaults to uniform parameter.


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