Progress Has Been Made. Canvas Experiment Thirteen

[elfs]

Canvas Experiment Thirteen

Looks almost like the finished product. The easing algorithm is the one thing left to do: Between one arbitarary position and another, "ease" the upper point to an angle between the point found with arcsin(), and the point found with ordinary radial arithmetic.

Comments

[blaisepascal]

I'm assuming that by "easing" you are trying to keep the blue arc from being a noticeable wedge when it disappears by subtly changing the angle of the arch edges as the arc shrinks?

arcsin() isn't giving you a point, it's giving you an angle. You might be able to use that insight to your advantage...

Here's an idea: Given an arc nominally between θ and φ, the outer edges of the arc on actually range from θ+δ to φ-δ, while the inner edges range from θ+ε to φ-ε. So how about changing your angle offsets by 2ε/(φ-θ) for the inner edge, and 2δ/(φ-θ) for the outer edge.

It will have the flaw that the nominal radial line does not remain one one side of the moving edge, but you can't see the radial line anyway.