John Carmichael wrote:

> I've never heard of a "Bezier Curve".  Is this the type of curve that Delta
> Cad draws when you use the "Spline" feature to connect points?
>
> John

Possibly. A Bezier curve is a specific flavor of cubic spline. They are very
quick to draw and easy to connect to one another to create a composite curve
with desirable properties such as continuity of curvature.

I don't know what Delta Cad offers, but typically you would specify the
positions of the ends of the curve and the positions of two other control
points. The curve goes from one end towards the first control point, then
gradually swerves towards the other and finally towards the end point. It does
not, in general, pass through the control points. By positioning the control
points, you can totally control the slope at the end points and you have some
control over where the curvature takes place along the curve.

With a single Bezier you can achieve a C or S shaped curve or a loop, like the
letter gamma, so with two you can make a figure 8. Whether you can reproduce an
analemma to within, say, one minute of time, I don't know but I bet you could.
You'd have to experiment with the best places to break the analemma into two
sections. The solstices might be good.

Beziers are great but there are things they cannot do. For instance, they
cannot accurately follow a circular arc.

Hope this helps


Chris Lusby Taylor
51.4N, 1.3W, 100%cloudy today


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