← Back to Tutorials

Control and Modulation

Beginner Composer

Use ClockFr, LfoFr, and Smooth to drive parameters across audio and GPU operators.

What is the Control domain?

Control operators produce scalar values — numbers that change over time, running at frame rate (~60 Hz) on the main thread. They're Vivid's modulation layer.

A Control output (orange wire) can connect to any numeric parameter on any operator, regardless of domain — GPU, Audio, or another Control operator. This is how you animate parameters without writing code.

Core Control operators

Operator What it produces
ClockFr Beat phase (0–1 sawtooth), beat trigger impulse
LfoFr Periodic oscillation at a set frequency or beat division
Smooth Exponential smoother with independent rise and fall times
Envelope ADSR shape triggered by a gate signal
Math Arithmetic on control signals: add, multiply, remap

Exercise 1: LFO driving a parameter

The simplest modulation: an LfoFr driving a single parameter.

  1. Add Metaball → video_out
  2. Add LfoFr. Connect lfo1/value → metaball/pos_x

The Metaball sweeps left and right at 1 Hz.

Key LfoFr params: - frequency — oscillation rate in Hz (or beat division in sync mode) - amplitude — output range is ±amplitude around the center - offset — shifts the center point - waveform — sine, saw, square, triangle, random - polarity — bipolar (−1 to +1) or unipolar (0 to 1)

Exercise 2: Sync LFO to a tempo

LfoFr can lock to a beat clock instead of running freely.

  1. Add ClockFr. Set bpm to 120.
  2. Connect clock1/beat_phase → lfo1/beat_phase
  3. On LfoFr, set rate_mode to sync

The LFO now cycles exactly once per beat at 120 BPM. Change sync_division to make it cycle every 2 beats, every bar, etc.

ClockFr also outputs beat_trigger — an impulse at each beat boundary. This is useful for triggering one-shot events rather than continuous oscillation.

Exercise 3: Smooth for slew and envelope following

Smooth applies exponential lag to a signal, with independent time constants for rising and falling edges.

  1. Connect any fast-changing signal (e.g., LfoFr with square wave) to smooth1/input
  2. Connect smooth1/value → a parameter

Key Smooth params: - rise_time (seconds) — how long to slew up to a new higher value - fall_time (seconds) — how long to decay to a new lower value

Set rise_time = 0.005 and fall_time = 0.4 to get a fast attack / slow release shape — the standard envelope-follower feel used in audio-reactive visuals.

Exercise 4: One LFO, two domains

Control signals are domain-agnostic. The same LfoFr output can wire into an audio parameter and a GPU parameter simultaneously.

  1. Start with Oscillator → Gain → audio_out
  2. Start with Metaball → video_out
  3. Add LfoFr
  4. Connect lfo1/value → osc1/frequency (audio parameter — hear the pitch wobble)
  5. Connect lfo1/value → metaball/pos_x (GPU parameter — see it move)

Both audio and GPU are now locked to the same modulation source. This is the foundation of synchronized AV performance.

What's happening

ClockFr → LfoFr/beat_phase     (sync to tempo)
LfoFr/value → Oscillator/freq  (audio modulation)
LfoFr/value → Metaball/pos_x   (GPU modulation)

The Control domain runs at frame cadence and delivers scalar values on every frame tick. When a Control output connects to an audio-domain parameter, the value is sampled once per audio buffer (bridged via the AudioFrameBridge). The audio engine interpolates smoothly between frames, so no zipper noise occurs.

Next steps