Pretransform channel node

Takes translate, rotate, and/or scale channels and transforms them using the pretransform of the given object.

This CHOP takes translate, rotate, and/or scale channels and transforms them using the pretransform of the given object. It is primarily used remove the pretransform of a destination object from the output of Object/Transform CHOPs before exporting to the destination object. A combination of Object, PreTransform, and Export CHOPs can be used to perform orientation constraints in objects.

If no input is given, then channels are simply generated from the given object’s pretransform. If an input is given, the interpretation of the channels as a transform are defined by the Input Transform Order, and Translate/Rotate/Scale/Pivot Scope parameters. Any missing transform channels from an input are filled in using the default value of 1 for the scales, and 0 for all others. The input transform is then right-multiplied by the (usually inverse) pretransform.

To affect only one set of channels coming into the CHOP, use the Scope parameter.

Parameters

PreTransform

Object	The name of the object to take the pretransform from
Invert PreTransform	Invert the pretransform (This option should be on to remove the pretransform from the input channels.)
Input Transform Order	The transform order of the input channels
Translate/Rotate/Scale/Pivot Scope	The names of the input transform channels
Out Transform Order	The transform order used to generate the output channels
Out Pivot	The pivot used to generate the output channels

Channel

Channel Names

The output channel names. This can be used to include the object name in the generated channels. If Input Channels is chosen, then the channels will use the same names as its input. If there is no input, then Input Channels behaves the same as Channel Name.

Channel Range

Indicates how much of the channel to cook.

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

Start

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

End

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

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