Hey there,
i had the same idea and wrote two processing sketches where you can draw curves and store their information in a .txt file.
https://bitbucket.org/dinigrosmer/multiplecurves
The saveMultipleCurve.pde is drawing a curve as a combination of two mathematical functions (f(x) = a1x^2 + b1x; g(x) = a2x^2 + b2x + c2) and translates and rotates them. Everything gets saved to the data.txt in the order:
angle \t x2 \t x3 \t a1 \t b1 \t a2 \t b2 \t c2 \t translate X \t translate Y
where x2 is the functions maximum and x3 the ending point. TranslateX and translateY gives you the curves starting point.
loadMultipleCurves.pde is doing what i intend the arduino should be doing: everything backwards, reading the 10 numbers and then drawing a curve from it.
I have no idea if this is working. I'm stuck on lonely island for two months and can't try this on an arduino connected to two steppers, so if you or anybody can try this, give a feedback.