On Tuesday, 20 September 2016 at 12:35:18 UTC, Basile B. wrote:

I've recently started an easing/interpolation family offunction in my D user library. It's based on something I knowwell since I've already used them in 2012 in a VST plugincalled GrainPlot (RIP).## Advertising

However for one of the function, I can't manage to get theinverse.[...] The problem is here: https://github.com/BBasile/iz/blob/master/import/iz/math.d#L849 - f(x,c) = 1.0 - pow(1.0 - pow(x, 2.0/c), c * 0.5); - c(f0.5)) = ? Which means that I ask you if you can isolate c for y = 1.0 - pow(1.0 - pow(0.5, 2.0/c), c * 0.5); y is always f(0.5,c)

`If you don't understand, these function have a control point, for`

`"parabol" and "pow" it's easy to get the c Coefficient that`

`manages the slope. But for the ellipse (aka the super ellipse)`

`it's a math nightmare !!!!)`

`For example is use the three functions in the same order`

`(parabol, pow, ellipse):`

http://sendvid.com/ygti5jmr

`for the ellipse you can see that the mouse position is not in`

`sync with the control point at the middle...it's the problem.`

`I need to isolate c when "y = 1.0 - pow(1.0 - pow(0.5, 2.0/c), c`

`* 0.5)".`

I know it's hard...otherwise I wouldn't ask ;]