NumberSequence

The NumberSequence data type represents a series of number values from 0 to 1. The number values are expressed using the NumberSequenceKeypoint type. This type is used in properties such as ParticleEmitter.Size and Beam.Transparency to define a numerical change over time.

Equality

Two NumberSequence objects are equivalent only if the values of their NumberSequenceKeypoint are equivalent, even if both would result in similar graphs.

Evaluation

The NumberSequence type does not have a built-in method for getting the value at a certain time/point because keypoints can have random envelopes. However, assuming the envelope values of your keypoints are all 0, you can use the following function to evaluate at a specific time.

local function evalNumberSequence(sequence: NumberSequence, time: number)
    -- If time is 0 or 1, return the first or last value respectively
    if time == 0 then
        return sequence.Keypoints[1].Value
    elseif time == 1 then
        return sequence.Keypoints[#sequence.Keypoints].Value
    end

    -- Otherwise, step through each sequential pair of keypoints
    for i = 1, #sequence.Keypoints - 1 do
        local currKeypoint = sequence.Keypoints[i]
        local nextKeypoint = sequence.Keypoints[i + 1]
        if time >= currKeypoint.Time and time < nextKeypoint.Time then
            -- Calculate how far alpha lies between the points
            local alpha = (time - currKeypoint.Time) / (nextKeypoint.Time - currKeypoint.Time)
            -- Return the value between the points using alpha
            return currKeypoint.Value + (nextKeypoint.Value - currKeypoint.Value) * alpha
        end
    end
end

local numberSequence = NumberSequence.new{
    NumberSequenceKeypoint.new(0, 0),
    NumberSequenceKeypoint.new(0.5, 1),
    NumberSequenceKeypoint.new(1, 0),
}

print(evalNumberSequence(numberSequence, 0.65))  --> 0.7