hammax wrote: ↑Thu Dec 14, 2017 2:14 pm

@Chris_G: some more questions about sweep_2_rail.

Working with that tool, one can find some parametrization-options.

- Continuity is almost selfexplaining - are there any recommendations?

- Parametrization grants 4 items - not so clear - a trial and error thing: Any recommendations?

- Smoothing Algorithm - 3 possible Parameters - maybe also a testing and experience thing: Any recommendations?

This tool is not sweep_2_rails. It is the approximate tool.

One good way to feel how these settings work is to discretize an edge with few points (and eventually change the discretization method to get regularly or not regularly spaced points) and create an approximate curve on them.

You can then check the properties of the approximation curve with a comb plot, and the GeomInfo tool.

Even though there is nothing scientific in this, you end up getting a kind of feeling of the "quality" of the approximation curve :

- how many control points (less is better)

- how the control points are distributed (high-degrees can give CPs that are distributed in a very chaotic way)

Then you can suppose the same will apply to approximation surfaces.

hammax wrote: ↑Thu Dec 14, 2017 2:14 pm

- Continuity is almost selfexplaining - are there any recommendations?

It depends on what you want to do.

C# continuities are mathematical continuities. On a visual point of view, they don't really offer any value over their G# conterparts.

G1 is usually good enough for curves. They will look perfectly smooth. Inkscape only offers C1 continuous paths at best, and that's OK.

But on surfaces (or curves that will be used to generate surfaces later) then G2 will be better, and G3 will offer a visually perfectly smooth surface.

hammax wrote: ↑Thu Dec 14, 2017 2:14 pm

- Parametrization grants 4 items - not so clear - a trial and error thing: Any recommendations?

If the points you are approximating are regularly spaced, the parametrization setting will have a very low influence.

hammax wrote: ↑Thu Dec 14, 2017 2:14 pm

- Smoothing Algorithm - 3 possible Parameters - maybe also a testing and experience thing: Any recommendations?

The smoothing algo can be pretty interesting but it has some limitation.

It tries to find a curve (or surface) that minimizes the properties according to the supplied weights.

Curve properties :

CL = curve length

CC = curve curvature

CT = curve torsion

Algo settings :

WL = algo length weight

WC = algo curvature weight

XT = algo torsion weight

The algo tries to find the minimal criterion CL*WL + CC*WC + CT*WT

So you assign a high value to torsion weight to get a curve with the least possible torsion, a high value to curvature weight to get a curve with the least possible curvature, etc.

However the algo will not produce a curve or surface with continuity higher than C2.