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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