(I just called it the ‘Kolson Method’ here just to differentiate it from the ‘Sspencer Method’, etc.)
(Mod Edit: As of January 2019, Keith put a more complete tutorial on the wiki: Creating Smooth Curves: The Kolson Method - Seamly2D)
Based on my (somewhat limited) experience with V, here is what you need to watch out for:
- Always do curves last. They depend on control/reference points and lines that must be in place before you place your curves. It’s an issue with V itself, which needs to be dealt with at some point.
- Never do freehand curves. Use formulas for setting the position of control/reference points. If you don’t, they won’t be nearly as easy to make work, and won’t work at all with different measurements.
- Unless you are doing something fancy, all curve ends must be at ninety degrees to the lines that they attach to. This is to ensure that when you sew the other half of the garment together, where the two curves meet forms a smooth line. (i.e. 90° + 90° = 180° - a straight line.)
Setting up a curve using reference points like I do in the example isn’t hard. (I used
X as a prefix for control/reference points to keep my main numbering simple. You’ll also notice that I drag the point labels around to make things neater.)
- Use the ‘
Point from X and Y of two other points’ tool based on adjoining points on the curve (
- Create lines between the reference points and the curve points (light-blue, dashed lines).
- Use the ‘
Curved path’ tool to lay your curve. (Don’t worry if it looks like crap, to begin with.)
- Right-click the curve and select ‘
- For each curve point, make sure that the control point angles are at right angles to whatever lines they are attached to. (If a line isn’t attached to a point, see if it makes sense to be oriented horizontal or vertical, like
A16in my example.)
- For the length of the first control point of each curve point, use the line length from the previous reference point (
X3in the example) to the previous curve point (
A16in the example) and multiply by
.55. (The proper value is
0.551915, but that much precision isn’t needed; just remember `.55’. This value makes bezier curves come closest to approximating the curve of a circle, which makes for the smoothest curves.)
- For the length of the second control point, do the same thing, but with the next reference and curve points. (
A32in the example).
As you can see by my example, even odd armhole curves can turn out very smoothly, and changing any measurement won’t bother their result in the slightest.
Hope this helps!
[Update 1: I will be editing this first post as needed over the next few days. I just finished walking through the process in V. and took four dozen screenshots(!) to support the text. I’m taking a break now, but plan to get at least the images up and some of the text later today.]