SpringEasing.lua

local SpringEasing = {}

-- EASING

local inflectX, inflectY = 0.075, 0.2
local outflectX, outflectY = 1 - inflectX, 1 - inflectY
local decay = 12

local function springIn(progress)
	return progress ^ 4
end

local function springOut(progress)
	return -(2 ^ (-decay * progress)) + 1
end

local function springInOut(progress)
	if progress < inflectX then
		return inflectY * springIn(progress / inflectX)
	end
	return outflectY * springOut((progress-inflectX) * outflectX) + inflectY
end

local function springEase(t, tMax, start, delta)
	return start + (delta * springInOut(t / tMax))
end

-- PUBLIC

function SpringEasing.transition(object, options)
	if options.time == nil then
		options.time = 600
	end
	options.transition = springEase
	return transition.to(object, options)
end

return SpringEasing