Houdini 19.0 Nodes Channel nodes Extract Pose-Drivers

Extract Pose-Drivers channel node

Creates channels from the specified derived transforms, node parameters and CHOP channels for pose-space deformation.

Since 17.0

This CHOP creates a set of channels from a specified set of pose-drivers. For each driver, one or more channels are created and named with this node’s name and the driver index. Their values are determined by the driver’s type. For a Transform driver, the channels are derived from the specified OBJ node using the transform type and mapping to select and map the object’s transforms. For the Parameter driver, the channels retrieved as parameters from the specified OBJ node. For a Channel driver, the channels are retrieved from the specified CHOP node.

This CHOP is used by the Pose-Space Deform SOP, which indirectly finds this node in its provided geometry library.



Show All Parameters

Disabling this toggle simplifies the interface to make the parameters and the values easier to work with.

Geometry Path

Path to a SOP node containing bone capture attributes from which the transforms are derived. Usually the SOP node will lie upstream of a Bone Deform SOP because it removes the bone capture attributes by default.

Skeleton Root Path

Specifies the parent OBJ for the bones attached to the input geometry. The pCaptSkelRoot detail attribute is used by default when this parameter is empty. If this parameter is non-empty, it overrides the pCaptSkelRoot detail attribute in the input geometry.

Channel Name Prefix

Specifies a prefix for the name of the channels created by this node. If empty the name of this node is used as the channel name prefix.

Number of Drivers

Number of drivers. Each driver creates one or more channels in the output.


Specifies the source of the driver channels.

Local Transform

Specified OBJ node’s local transform.

Effective Local Transform

Product of the specified OBJ node’s pre-, local, region and constraint transforms.

Object Local Transform

Transform of the specified OBJ node relative to the subnet given by the Skeleton Root Path.

Relative Transform

Transform of the specified OBJ node relative to the _Relative OBJ Node__.

World Transform

Specified OBJ’s world transform.

CRegion World Transform

Product of all transforms influencing the specified OBJ node including its capture region.

Parameter Path

Select parameters of interest on the OBJ at the Skeleton Root Path.

CHOP Channel Path

Select channels of interest produced by the CHOP Channel Path.

OBJ Node

Specified OBJ node for pose-drivers.


Specifies the transform of interest for this transform driver, usually a combination of rotation, scale, and translation. Rotations are given in Euler rotation angles. Other driver transforms include:

Quaternion (Rot.)

Euler rotations are changed to Quaternion coordinates. The negated quaternion coordinates are also output.

Dual Quaternion (Rot. and Tran.)

Euler rotations and Cartesian translations are changed to dual Quaternion coordinates. The negated rotation quaternion coordinates are also output.

Matrix Exponential

The transformation matrix is changed to the exponential of the transformation matrix.

CHOP Channel Path

Specifies the path to a CHOP node and channel (e.g. /obj/chopnet1/constant1:chan1).

Parameter Path

Specifies the path to a node and parameter (e.g. /obj/chain_bone1/r).

Relative OBJ Node

Specifies the parent OBJ node that is used with Relative Transform type drivers.


Scaling may be necessary to modulate driver values that are much larger or smaller than those produced by other drivers.


Offset is applied before scaling to center its range of values.


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.


The start time of the channel range.


The end time of the channel range.

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.


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


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:


Matches a single channel name.

chan3 tx ty tz

Matches four channel names, separated by spaces.


Matches each channel that starts with chan.


The ? matches a single character. t? matches two-character channels starting with t.


Matches channels rx, ry and rz.


Matches number ranges giving blend3, blend5, and blend7.


Matches channels blend2, blend3, blend5, blend13.


[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.


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).


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.


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.


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.

See also

Extract Pose-Drivers