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 Audio Oscillator CHOP, the LFO CHOP is designed for non-audio frequencies.
Parameters - LFO Page
wavetype - ⊞ - The shape of the waveform to repeat, unless overridden by the Source Wave:
tri- (-1 to 1) A ramp-up to 1 and ramp-down to -1 that can be shaped with the Bias parameter.
frequency - The cycles per second of the oscillation. When the Octave Control input is connected, it alters the frequency exponentially.
offset - Values output from the CHOP can have an offset added to them.
amp - Values output from the CHOP can be scaled.
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 - A value of .5 is a phase shift of 180 degrees, or one half cycle.
resetcondition - ⊞ - This menu determines how the Reset input triggers resetting the channel(s).
- Off to On
offtoon- Channels are reset when the Reset input goes off to on.
- While On
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
ontooff- Channels are reset when the Reset input goes on to off.
- While Off
off- Channels are reset when the Reset input goes off. The channel will hold the reset value until the input turns on.
reset - This button resets the channel(s) to 0.
Parameters - Channel Page
channelname - 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.
rate - The sample rate of the CHOP. The default sample rate is 60 samples per second.
Parameters - Common Page
timeslice - Turning this on forces the channels to be "Time Sliced". A Time Slice is the time between the last cook frame and the current cook frame.
scope - To determine which channels get affected, some CHOPs use a Scope string on the Common page.
Sample Rate Match
srselect - ⊞ - Handle cases where multiple input CHOPs' sample rates are different. When Resampling occurs, the curves are interpolated according to the Interpolation Method Option, or "Linear" if the Interpolate Options are not available.
- Resample At First Input's Rate
first- Use rate of first input to resample others.
- Resample At Maximum Rate
max- Resample to the highest sample rate.
- Resample At Minimum Rate
min- Resample to the lowest sample rate.
- Error If Rates Differ
err- Doesn't accept conflicting sample rates.
exportmethod - ⊞ - This will determine how to connect the CHOP channel to the parameter. Refer to the Export article for more information.
- DAT Table by Index
datindex- Uses the docked DAT table and references the channel via the index of the channel in the CHOP.
- DAT Table by Name
datname- Uses the docked DAT table and references the channel via the name of the channel in the CHOP.
- Channel Name is Path:Parameter
autoname- The channel is the full destination of where to export to, such has
autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.
exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).
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To pulse a parameter is to send it a signal from a CHOP or python or a mouse click that causes a new action to occur immediately. A pulse from a CHOP is typically a 0 to 1 to 0 signal in a channel, and a pulse via python is via a
.pulse() call on a pulse-type parameter, such as Reset in a Speed CHOP.
samples-per-second of a CHOP. Each CHOP in your network has a sample rate, whether it is used or not. The overall timeline has a "frame rate", which is the number of animation frames per second, generally your monitor display frequency.
A Time Slice is the time from the last cook frame to the current cook frame. In CHOPs it is the set of short channels that only contain the CHOP channels' samples between the last and the current cook frame.
A parameter in most CHOPs that restricts which channels of that CHOP will be affected. Normally all channels of a CHOP are affected by the operator.
Exporting is the connection of CHOP channels to parameters of operators. The output of each exporting CHOP is one or more channels, active only while the CHOP Viewer is on. The current value of a channel can be exported to a parameter of any operator, overriding that parameter's value. See Parameter.
Parameters in TouchDesigner are an operator's settings (numbers, menus, flags, strings, paths) which the user can alter. Parameters for any operator can be opened by right-clicking on the operator and selecting "Parameters..." A currently selected operator's parameters can be viewed in a Network Editor by pressing the keyboard shortcut 'p'.