ObjectChain channel node

Creates channels representing the transforms for a chain of objects.

See also: Object, Transform, IKSolver

The ObjectChain CHOP takes a chain of objects and returns information on their transforms.

Tip

This node is especially useful for generating transforms for the IKSolver CHOP.

Parameters

Object Chain

Start Object	The start object of the chain to obtain transforms from. This object must be an input ancestor of the End Object.
End Object	The end object of the chain to obtain transforms from. This object must be an output descendent of the Start Object.
Pre-transform Name	If enabled, pre-transforms from the objects are generated as separate tranforms. The text specified here is used as part of the generated channel name to differentiate it from the regular transform channels.
Fetch Bone Rest Channels	If enabled, this will generate additional channels for these Bone object parameters: Rest Angles, Bone Length, and Dampening. This is useful for generating channels used by the IKSolver CHOP.
Fetch Bone Constraint Channels	If enabled, this will generate additional channels for these Bone object constraint parameters: X/Y/Z Angle Range, X/Y/Z Damping Angle, X/Y/Z Damping Rolloff. This is useful for generating channels used by the IKSolver CHOP.
Fetch Local Transforms	If enabled, this will generate local transforms for each of the objects in the specified chain. If disabled, full world transforms will be generated instead.

Channel

Channel Names

Sets how the output channels are named.

Channel Name	Only use the name of the channel.
OP and Channel Name	Include the name of the object with the channel name, separated by a colon (:).
Full Path and Channel Name	Include the full path of the object with the channel name, separated by a colon (:).

Channel Range

Indicates how much of the channel to fetch.

Use Full Animation Range	All of the current global animation range.
Use Current Frame	Only the sample at the current frame.
Use Start/End	Specify the range.

Start

The start time of the desired interval of the object path.

Note

The value of this parameter is interpreted using the Units parameter on the Common parameters tab.

End

The end time of the desired interval of the object path.

Note

The value of this parameter is interpreted using the Units parameter on the Common parameters tab.

Sample Rate

The sampling rate of the channel in frames per second (Hz).

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.

Usages in other examples

Example name	Example for
SimpleTransformChain	TransformChain channel node	Load \| Launch
SimpleIKSolver	IKSolver channel node	Load \| Launch