Wave channel node

Creates a waveform that is repeated.

All

Parameters

Local variables

This CHOP produces a variety of waveforms. On top of the actual waveform, an offset, decay and ramp can be applied.

Multiple channels can be generated by using patterns in the Channel Name parameter. A few examples of name pattern generation:

tx ty tz             tx ty tz
t[xyz]               tx ty tz
chan[1-4]            chan1 chan2 chan3 chan4
c[xyz][1-3:2,15]     cx1 cy1 cz1 cx3 cy3 cz3 cx15 cy15 cz15

These parameters are applied in the following order: Offset, Amplitude, Decay, Ramp, and Expression.

Parameters

Waveform

Type

The wave type which is one of the following:

Constant	A constant valued “wave”.
Sine	A sine wave.
Gaussian	A Gaussian wave (also known as bell or normal curve).
Triangle	A triangular sawtooth wave.
Square	A square wave.
Pulse	A periodic one-sample pulse wave.
Expression	A user defined non-periodic expression.

Period

The period of the wave.

Phase

The phase of the wave, from 0 to 1.

Bias

The bias of the waveform. Only Gaussian, triangle and square waves have biases.

Offset

The value offset of the waveform.

Amplitude

The amplitude of the waveform.

Decay Rate

The decay rate of the waveform, represented as the fraction of decay after 1 Unit of time (default is one second)

Ramp Slope

A ramp is added the wave: amount per Unit of time.

Expression

Expression to use for “Expression” Type.

Channel

Channel Name	The names of the channels to create. Patterns like `chan[1-20]` generate multiple channels.
Start, End	The start time of the channels.
Sample Rate	The sample rate of the channels.
Extend Left	The left extend conditions.
Extend Right	The right extend conditions.
Default Value	The default value for extend conditions.

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.

Local variables

I	The current index.
L	The current loop index, which is reset every period.
N	The current period count, starting at zero.
C	The current channel (0 to NC-1).
NC	The total number of channels.
P	The period of the wave (from the Period parameter).
PH	The phase of the wave (from the Phase parameter).
B	The bias of the wave (from the Bias parameter).

Usages in other examples

Example name	Example for
CopyChannels	Copy channel node	Load \| Launch
Shift	Shift channel node	Load \| Launch
Extend	Extend channel node	Load \| Launch
Slope	Slope channel node	Load \| Launch
Constant02	Constant channel node	Load \| Launch
Rename	Rename channel node	Load \| Launch
LagBasic	Lag channel node	Load \| Launch
Delay	Delay channel node	Load \| Launch
Envelope	Envelope channel node	Load \| Launch
Sequence	Sequence channel node	Load \| Launch
MathBasic	Math channel node	Load \| Launch
Cycle	Cycle channel node	Load \| Launch
Export	Export channel node	Load \| Launch
Stretch	Stretch channel node	Load \| Launch
LimitBasic	Limit channel node	Load \| Launch
Composite		Load \| Launch
Blend	Blend channel node	Load \| Launch
MergeBasic	Merge channel node	Load \| Launch
Area with one input	Area channel node	Load \| Launch
Area with three inputs	Area channel node	Load \| Launch
Area with two inputs	Area channel node	Load \| Launch
ChannelSOPColorExample	Channel surface node	Load \| Launch