Envelopes

envelopes.js

// Fade Ins:
    // Linear:
    for (let i = 0; i < length; i++) {
        array[i] = i / length;
    }

    // Exponential, Concave Up:
    let silence   = Math.pow(10.0, -120.0 / 20.0); // Silence is -120dB
    let fromValue = silence;

    let multiplier = Math.pow(1.0 / silence, 1.0 / length);

    for (let i = 0; i < length; i++) {
        result[i] = fromValue;
        fromValue *= multiplier;
    }

    // Quadratic, Concave Up:
    for (let i = 0; i < length; i++) {
        array[i] = Math.pow(, 2);
    }

    // Cubic, Concave Up
    for (let i = 0; i < length; i++) {
        array[i] = Math.pow(i / length, 3);
    }

    // Quadratic, Concave Down
    for (let i = 0; i < length; i++) {
        array[i] = 1.0 + Math.pow((i / length) - 1.0, 2);
    }

    // Cubic, Concave Down
    for (let i = 0; i < length; i++) {
        array[i] = 1.0 + Math.pow((i / length) - 1.0, 3);
    }


// Fade Outs:
    // Linear
    for (let i = 0; i < length; i++) {
        array[i] = 1.0 - (i / length);
    }

    // Exponential, Concave Up:
    let silence   = Math.pow(10.0, -120.0 / 20.0); // Silence is -120dB
    let fromValue = 1.0;

    let multiplier = Math.pow(silence, 1.0 / length);

    for (let i = 0; i < length; i++) {
        result[i] = fromValue;
        fromValue *= multiplier;
    }

    // Quadratic, Concave Up
    for (let i = 0; i < length; i++) {
        array[i] = Math.pow(1.0 - (i / length), 2);
    }

    // Cubic, Concave Up
    for (let i = 0; i < length; i++) {
        array[i] = Math.pow(1.0 - (i / length), 3);
    }

    // Quadratic, Concave Down
    for (let i = 0; i < length; i++) {
        array[i] = 1.0 - Math.pow(1.0 - (i / length), 2);
    }

    // Cubic, Concave Down
    for (let i = 0; i < length; i++) {
        array[i] = 1.0 - Math.pow(1.0 - (i / length), 3);
    }

// Exponential (Both):
    let silence   = Math.pow(10.0, -120.0 / 20.0); // Silence is -120dB
    let fromValue = isFadeIn ? silence : 1.0;
    let toValue   = isFadeIn ? 1.0 : silence;

    let multiplier = Math.pow(toValue / fromValue, 1.0 / length);

    for (let i = 0; i < length; i++) {
        result[i] = fromValue;
        fromValue *= multiplier;
    }