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ScriptedInterpolator Protocol

Overview​

ScriptedInterpolator is a runtime-backed protocol for custom interpolation behavior.

Runtime status

This protocol is validated against upstream runtime-v0.1.64 (b25a322) and tracked in the 2.37.6 runtime baseline audit (May 12, 2026).

Use it when linear interpolation is not enough and you need script-defined easing at the interpolation level.

Type Shape​

export type ScriptedInterpolator<T> = {
    init: ((self: T, context: Context) -> boolean)?,
    transform: ((self: T, factor: number) -> number)?,
    transformValue: ((self: T, valueFrom: number, valueTo: number, factor: number) -> number)?,
} & T

Optional methods​

  • transform(self, factor) -> number
  • transformValue(self, valueFrom, valueTo, factor) -> number

Runtime fallback behavior​

If a method is omitted or errors, runtime falls back to standard linear behavior.

  • Missing/failed transform -> returns original factor
  • Missing/failed transformValue -> uses from + (to - from) * factor

Template​

export type MyInterpolator = {
    strength: Input<number>,
}

function transform(self: MyInterpolator, factor: number): number
    local t = math.max(0, math.min(1, factor))
    return t * t
end

function transformValue(self: MyInterpolator, valueFrom: number, valueTo: number, factor: number): number
    local t = transform(self, factor)
    return valueFrom + (valueTo - valueFrom) * t
end

return function(): ScriptedInterpolator<MyInterpolator>
    return {
        transform = transform,
        transformValue = transformValue,
        strength = 1,
    }
end

Exercise 1: Build a Quadratic Ease-In Mapper ⭐⭐​

Premise​

You are implementing interpolation math that should start slow and accelerate.

Starter Code​

local function transform(factor: number): number
    -- TODO: clamp to [0, 1], then return quadratic ease-in
    return factor
end

local function transformValue(valueFrom: number, valueTo: number, factor: number): number
    -- TODO: map transform(factor) across [valueFrom, valueTo]
    return valueFrom
end

local result = transformValue(10, 30, 0.5)
print(string.format("ANSWER: %.1f", result))

Expected output​

ANSWER: 15.0

Verify Your Answer​

Verify Your Answer

Knowledge Check​

Q:What happens if transformValue is not implemented in ScriptedInterpolator?

Next Steps​