Houdini 19.0 Nodes Channel nodes Constraint Object Pretransform

Constraint Object Pretransform channel node

Returns an Object Pretransform.

Since 16.0

The Constraint Object Pretransform CHOP returns an Object pretransform.


Constraint Pretransform

Transform Order

Transform Order

The left menu chooses the order in which transforms are applied. For example: scale, then rotate, then move. This can change the position and orientation of the object, in the same way that going a block and turning east takes you to a different place than turning east and then going a block.

The right menu chooses the order in which to rotate around the X, Y, and Z axes. Certain orders can make character joint transforms easier to use, depending on the character.

Target Object

The object that is being compared to the reference object.



The alignment option to use.

Extend to Min/Max

Find the earliest start and latest end, and extend all inputs to that range using the extend conditions.

Stretch to Min/Max

Find the earliest start and latest end, and stretch every channel’s start and end to that range.

Shift to Minimum

Find the earliest start and shift all channels so they all start at that index. All channels are extended to the length of the longest one.

Shift to Maximum

Find the latest end and shift all channels so they all end at that index. Extend all channels to the length of the longest one.

Shift to First Interval

Shift all channels to the start of the first channel and sample all inputs using the first input’s range.

Trim to First Interval

Trim all channels to first channel’s range.

Stretch to First Interval

Stretch all channels to the first channel’s range.

Trim to Smallest Interval

Trim all channels to the smallest start/end interval. The start and end values may not come from the same channel.

Stretch to Smallest Interval

Stretch all channels to the smallest start/end interval. The start and end values may not come from the same channel.


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.


The start time of the channel range.


The end time of the channel range.

Sample Rate

The sample rate of the CHOP.

Number of Threads

The number of separate threads to use to evaluate the channel samples. The default is no threading.

Since Houdini evaluates the VEX program for each sample in the input geometry, it can benefit greatly from threading on a multi-processor or multi-core machine when the CHOP nodes have many samples.


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

Constraint Object Pretransform