Composite channel node

Layers (blends) the channels of one CHOP on the channels of another CHOP.

All Parameters Local variables Example files

See also: Blend, Sequence

This CHOP layers (blends) the channels of one CHOP on the channels of another CHOP. The first input is the base input and the second is the layer input.

Over the interval of the layer, the layer channels are blended with the base channels. The contribution of the layer is eased-in and eased-out according to the Start, Peak, Release and End parameters. The base is unaffected outside the interval of the layer.

The Effect parameter determines the amount of contribution of the layer.

If Base Hold is 0, the layer input will completely replace the base input when the effect is 1. If Base Hold is 1, the layer will be added to the base.

The interval of the output starts at the minimum of the base and layer. The interval of the output ends at the maximum of the base and layer. The base’s extend conditions are used if the layer lies outside the base.

If the third input is supplied, the Effect page will be overridden by the third input’s first channel, which should contain the effect values over the range of the layer.

Parameters

Composite

Base Hold

Determines how much of the base to blend into the output at points where the layer has an effect.

Match By

Matches channels in the base input with ones in the layer input by either index or name. Channel Union causes layer channels that are not in the base to be added to the output.

Quaternion Blend

Aids in producing smooth rotation blending. The “quaternion” attribute should be in the input CHOP. See the Attribute CHOP.

Shortest Path Rotation Blending

If on, compensate for cyclic channels (such as angles) by always choosing the shortest route between samples when blending.

Rotation Scope

Defines which channels are rotations for Shortest Path Rotation Blending.

Cycle Length

The length of the cycle for Shortest Path Rotation Blending.

Effect

Effect

Sets how much the layer affects the output. If 0, the output is the base.

Unit Values

Sets the meaning of the next four parameters - either absolute values, relative to the start/end of the channel, or relative to the current frame. The layer and base are never shifted.

Start

The beginning of the composite interval. Effect is zero at this point.

Peak

Where the composite operation reaches maximum effect. This value is held until the release point.

Release

The point at which the effect begins to fall back towards zero.

End

The end of the composite operation’s effect. The effect reduces to zero again.

Rise/Fall Shape

The shape of the segment between the Start and Peak indices, or between Release and End.

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

C

The current channel index (0 to NC-1).

NC

The total number of channels.

Example files

Blend

$HFS/houdini/help

Load | Launch

You can chain the Composite CHOP together to take two or more channels and do an ordered sequence blend. The Composite CHOP takes a control curve and uses it to determine which channel to use with each Composite CHOP working on two channels at a time, creating a sequence blend. The first Composite node processes the first and second channel, the second Composite node processes the result from the first node and the third channel, and so on.

A key component of this network is the Limit CHOP. It processes the control curve so the range is valid for the pair of channels being processed by the associated Composite node.

Usages in other examples

Example name Example for
Composite

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