The whole unit circle situation should be scaled by r, but for the final equations, control point 1, r doesn't get multiplied to the y-term (k).
On a minor note, while reading this section, the TL;DR knowledge / assertion that I was looking for was that the vector-magnitudes of the control points from the start/end points were both the same, and equal to r*k (and the arc eqn for k, that was useful), in the direction of the circle tangent.
https://github.com/Pomax/BezierInfo-2/blob/ea6f610eadfb90a96efd2b2e9ea7460744d4d185/docs/chapters/circles_cubic/content.en-GB.md?plain=1#L86
The whole unit circle situation should be scaled by
r, but for the final equations, control point 1,rdoesn't get multiplied to the y-term (k).On a minor note, while reading this section, the TL;DR knowledge / assertion that I was looking for was that the vector-magnitudes of the control points from the start/end points were both the same, and equal to
r*k(and the arc eqn fork, that was useful), in the direction of the circle tangent.Thanks for the guide!