Ah. I withdraw my idea about no layers. The canvas plugin is more restricted than I thought.
I salute you for trying trial and error, I just did mine with some math. I googled “Bézier curve through three points”, or something like that and found a nice solution.
Say your three control points are: x0,y0, x1,y1, x2,y2
And you use qarp() to do the curve:
Repeat 10 times
— set t to loopindex/10
— X = qarp(x0, x1, x2, t)
— ... same for y...
The curve won’t pass over x1 though. To correct it do this:
X = qarp(x0, (4*x1-x0-x2)/2, x2, t)
... same for y ...
Now the curve will hit all three.