Oscillator channel node

Generates sounds in two ways.

See also: Warp, Wave

The Oscillator CHOP generates sounds in two ways. It synthesizes tones using a choice of common waveforms, or it repeats a prepared incoming audio clip of any duration.

When it is synthesizing tones from the basic waveforms, it steps through the waveform at a rate that depends on the Pitch Control input. By default, a Pitch Control of 0 gives a middle A at 440 Hz; A 1 gives 880 Hz; A -1 gives 220 Hz. Steps of 1 in Pitch Control are 1 octave apart. Steps of 1/12 (.08333) are 1 semitone apart.

Up to three input chops can be used.

Pitch Control

The first input affects the pitch. (It is “logarithmic”.) Output channels are generated for each Pitch Control channel.

Reset Pulse

The second (optional) input contains pulses that restart the oscillator from the beginning of the wave or the Playback Source. 0 in the input means “play the oscillator”. 1 means “stop the oscillator and cue it at the start of the waveform or Playback Source”.

Playback Source

The third (optional) input is a replacement of the waveform Type. It is a sound clip to play at a rate modified by the Pitch Control, and can contain any number of channels. These channels are generated for each Pitch Control channel. The Waveform Type and the Base Frequency parameters are disabled.

If you plug any sound clip into the Oscillator CHOP’s Playback Source, and Pitch Control is a constant value of 0 of any duration, it will just repeat the Playback Source. If you feed a Wave chop as its Pitch Control, it will raise and lower the speed/pitch of the input.

The Oscillator CHOP can serve as a general motion time-warper. If you put motion channels into the third input, you can control the time warp by feeding different Pitch Control curves. 0 pitch is normal speed, 1 is double speed.

Unlike the Waveform CHOP, this is an iterating chop, that is, it steps through the waveform while the pitch changes. To see this effect, feed a Wave CHOP into the Oscillator.

Parameters

Waveform

Type	The shape of the waveform to repeat. Sine, Gaussian, Triangle, Ramp, Square, Pulse
Base Frequency	Cycles per second when Pitch Control is 0.
Units per Octave	Amount that the Pitch Control needs to increase by to raise the pitch by one octave. The default of 1 means that a Pitch Control of 1 raises the pitch by one octave.
Offset	Values output from the CHOP can have an added to them.
Amplitude	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.
Phase	A value of .5 is a phase shift of 180 degrees, or one half cycle.
Smooth Pitch Changes	Samples the pitch curve for every sample between frames vs. using a single per-frame value.

Channel

Sample Rate

The sample rate of the CHOP.

Common

Some of these parameters may not be avaiable on all CHOP nodes.

Scope

To determine which channels get affected, some CHOPs have a scope string. Patterns can be used in the scope, for example * (match all), and ? (match single character).

The following are examples of possible channel name matching options:

`chan2`	Matches a single channel name.
`chan3 tx ty tz`	Matches four channel names, separated by spaces.
`chan*`	Matches each channel that starts with `chan`.
`foot`	Matches each channel that has `foot` in it.
`t?`	The `?` matches a single character. `t?` matches two-character channels starting with t.
`r[xyz]`	Matches channels `rx`, `ry` and `rz`.
`blend[3-7:2]`	Matches number ranges giving `blend3`, `blend5`, and `blend7`.
`blend[2-3,5,13]`	Matches channels `blend2`, `blend3`, `blend5`, `blend13`.
`t[xyz]`	`[xyz]`matches three characters, giving channels `tx`, `ty` and `tz`.

Sample Rate Match

The Sample Rate Match Options handle cases where multiple input CHOPs’ sample rates are different.

Resample At First Input’s Rate	Use rate of first input to resample others.
Resample At Maximum Rate	Resample to highest sample rate.
Resample At Minimum Rate	Resample to the lowest sample rate.
Error if Rates Differ	Does not accept conflicting sample rates.

Units

The units for which time parameters are specified.

For example, you can specify the amount of time a lag should last for in seconds (default), frames (at the Houdini FPS), or samples (in the CHOP’s sample rate).

Note

When you change the Units parameter, it does not convert the existing parameters to the new units.

Time Slice

Time Slicing is a feature which boosts cooking performance and reduces memory usage. Traditionally, CHOPs calculate the channel over its entire frame range. If the channel does need to be evaluated every frame, then cooking the entire range of the channel is unnecessary. It is more efficient to calculate only the fraction of the channel that is needed. This fraction is known as a Time Slice.

Unload

Causes the memory consumed by a CHOP to be released after it is cooked and the data passed to the next CHOP.

Export Prefix

The Export prefix is prepended to CHOP channel names to determine where to export to.

For example, if the CHOP channel was named geo1:tx, and the prefix was /obj, the channel would be exported to /obj/geo1/tx.

Note

You can leave the Export Prefix blank, but then your CHOP track names need to be absolute paths, such as obj:geo1:tx.

Graph Color

Every CHOP has this option. Each CHOP gets a default color assigned for display in the Graph port, but you can override the color in the Common page under Graph Color. There are 36 RGB color combinations in the Palette.

Graph Color Step

When the graph displays the animation curves and a CHOP has two or more channels, this defines the difference in color from one channel to the next, giving a rainbow spectrum of colors.

Usages in other examples

Example name	Example for