Drawable LFO shape

Audio Plugins
1

Hi,

I want to implement a simple version of LFO Tool as an exercise. How would I implement a drawable (by the user) waveshape that controls the (let’s say) volume modulation of the incoming audio signal.

What would be the best classes/logical flow? Or any similar examples I could look at?

Thank you.

2

an array of knots in the processor. every knot has a normalised x and y position as well as a value for the curviness of the neighboring line and a bool for dis/enabling it. in processBlock you interpolate over the curve in the desired way, like synced up to a phasor or so. in the editor you read the x, y and curve values, map them to width and height and also interpolate and draw the curve. a timerCallback waits for changes on the processor. maybe have an atomic bool for that. also implement mouse interactions for the knots in the editor

1 Like
3

what do you mean by knot? a knob?

4

What is it that you’d want the user to be able to draw? An LFO is defined by two parameters: frequency and amplitude. Not exactly something you’d normally draw by hand. You’d use 2 knobs or an XY pad or something. Are you looking for experience using LFOs, or in hand-drawing values for a parameter (such as gain) in a graph of some sort?

5

Have you used LFO Tool? Basically you can set a frequency synced to the host (for example 1/4 notes) and draw a wave shape by mouse which controls the volume (which cycles every 1/4 note). I’d like to let the user be able to draw that wave shape.

6

Take a look at this: GitHub - getdunne/juce-MultiStepEnvelopeGenerator

I think it is implemented exactly as @Mrugalla was outlining.

2 Likes
7

something like this:

struct Knot
{
    float x, y, shape;
    bool active;
};

to represent a point on the xy-pad and the intended shape of the line that leads to the next point

8

almost. it lacks the existence of an audio processor, resulting in the MSEG data being the same object as its representation in the editor