LFO CHOP

From TouchDesigner 099 Wiki

Summary

The LFO CHOP (low frequency oscillator) generates waves in real-time in two ways. It synthesizes curves using a choice of common waveforms like Sine or Pulse, or it repeats a prepared incoming curve.

It steps through the waveform at a rate that depends on the Frequency parameter and the Octave Control input. To watch its behavior, attach a Trail CHOP to its output and alter the Frequency parameter.

Up to three input CHOPs can be connected to the LFO CHOP:

Octave Control - Without this first (optional) input, the frequency is simply the Frequency parameter. If this input is connected, every unit doubles the frequency: When Octave Control is 1, the frequency is double, when it is 2 it is 4x, when it is -1 the frequency is half the Frequency parameter and when it is 0, there is no change in the frequency.

Reset - The seond (optional) input contains on-off (<=0 or >0) that restarts the channels of the oscillator from the beginning of the wave. The reset depends on the setting of the Reset Condition menu. By default, when the Reset input goes from off to on, it resets the wave and starts the waveform immediately. If Reset Condition is set to "While On", the reset value will be held until the Reset input goes off. Reset means "stop the oscillator and cue it at the start of the waveform".

Source Wave - The third (optional) input is a replacement of the waveform Type. It is a multi-sample CHOP curve and can contain any number of channels, limited to the channels defined on the Channel page. The waveform Type parameter is disabled.

The LFO CHOP can serve as a general motion time-warper and repeater. If you alter the Frequency, you can control the time warp.

Unlike the Wave CHOP, this is a time-sliced CHOP, that is, it generates its waveform as it goes, and speeds/slows how it steps through the waveform Type while the Frequency changes. Unlike the Oscillator CHOP, the LFO CHOP is designed for non-audio frequencies.

See also: Oscillator CHOP, Wave CHOP, Pulse CHOP.

PythonIcon.png lfoCHOP_Class

Parameters - Waveform Page

Type - The shape of the waveform to repeat, unless overridden by the Source Wave:

TouchChannels71.gif Sine (-1 to 1) A Sine wave.
TouchChannels74.gif Gaussian (0 to 1) A Gaussian (also known as a bell or normal) curve.
TouchChannels76.gif Triangle (-1 to 1) A ramp-up to 1 and ramp-down to -1 that can be shaped with the Bias parameter.
TouchChannels78.gif Ramp (0 to 1) A ramp from 0 to 1.
TouchChannels80.gif Square (-1 to 1) Step-up/step-down, with Bias control to make it rectangular.
TouchChannels82.gif Pulse (0 to 1) Produces a 1 for one sample, 0 otherwise.

Frequency /frequency - The cycles per second of the oscillation. When the Octave Control input is connected, it alters the frequency exponentially.

Offset /offset - Values output from the CHOP can have an offset added to them.

Amplitude /amp - Values output from the CHOP can be scaled.

Bias /bias - Shape control for Triangle, Gaussian and Square waves. For triangle waves, it moves the peak. For square waves, it alters the width of the peak. Zero means no bias.

Phase /phase - A value of .5 is a phase shift of 180 degrees, or one half cycle.

Reset - This button resets the channel(s) to 0.

Reset Condition - This menu determines how the Reset input triggers resetting the channel(s).

  • Off to On - channels are reset when the Reset input goes off to on.
  • While On - channels are reset when the Reset input goes on. The channel will hold the reset value until the input turns off.
  • On to Off - channels are reset when the Reset input goes on to off.
  • While Off - channels are reset when the Reset input goes off. The channel will hold the reset value until the input turns on.

Parameters - Channel Page

Channel Names - A list of the names of the channels. You can put patterns like chan[1-10] to generate 10 channels. See Pattern Expansion.

Each channel can be different by putting the channel index variable, $C in parameters like the frequency channel.

Sample Rate - The sample rate of the CHOP. The default sample rate is 60 samples per second.

Standard Options and Local Variables

$C - The current channel (0 to NC-1).
$NC - The number of channels.

Example: Put chan[1-10] in the Channels parameter. Put 1+$C in the Frequency parameter. The 10 channels should have frequency 1 to 10.

Example: Put chan[0-9] in the Channels parameter. Create a Constant CHOP with 10 channels starting with chan0, and put chop("constant1/chan$C") in the Frequency parameter. Adjust the sliders of the Constant CHOP and each of 10 channels should have a different frequency.