Channel channel node

Creates channels from the value of its parameters.

All Parameters Example files

See also: Constant

This CHOP allows you to create channels that replicate the values of its parameters through time. Each channel can be named and assigned a different value. The parameter is then evaluated for each frame in the scene file.

This operator can be created from existing channel groups by right-clicking on the name in the Channel Groups list and choosing Create Channel CHOP.

Parameters

Data

Copy to Export

Copies the animation from its Value parameters to where the channels are currently being exported to.

Update Value Aliases from Exports

Sets the channel aliases of the Value parameters to match where the channels are currently being exported to.

One Key Per Sample

Instead of evaluating the Value parameter every frame, create the channel such that each sample corresponds to a key on the Value parameter. This is only meaningful if the Value parameter is animated.

Add Node Name Dependencies

If set, this will cause the names specified in the Name parameter to be treated as real parameter paths and have name dependencies built for them. Then if the referenced nodes are renamed, the paths in the Name parameter will update accordingly.

Number of Channels

Number of channels to create.

Name

Name of the channel to create. If the size is greater than 1, then the letter x,y,z, or w is appended to the channel name depending on if it is the first, second, third, or fourth component of the Value parameter respectively.

Type

Type of channel to create.

Float

Regular float parameter

Euler Rotation

A quaternion attribute is added to the three generated channels.

Rotate Order

If the type is Euler Rotation, this parameter specifies the order of rotation.

Size

Number of components. If the type is Euler Rotation, this parameter has no effect since 3 components must be generated.

Value

The values of the channels.

Channel

Channel Range

Specifies the range of data to generate.

Use Full Animation Range

All of the animated range.

Use Current Frame

Only the sample at the current frame.

Use Start/End

The range is specified from the Start and End parameters.

Use Value Animation

The range is taken from range of keys available in the evaluated Value parameters.

Start

The start time of the channel range.

End

The end time of the channel range.

Sample Rate

The sample rate of the CHOP.

Extend Left

The left extend condition (before the CHOP’s start).

Extend Right

The right extend condition (after the CHOP’s end).

Default Value

The value to use for the “Default Value” extend condition type.

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.

Example files

ChannelBasic

$HFS/houdini/help/examples/nodes/chop/channel/ChannelBasic.cmd

Load | Launch

This is a simple example of using the Channel CHOP along with a Noise CHOP to add some variety to keyframed animation that can still be easily tweaked as keyframe animation. Notice that the object can be manipulated as usual in the viewport transparently. The values will be modified in the Channel CHOP.

Usages in other examples

Example name Example for
Lookup

Lookup channel node

Load | Launch