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This CHOP shortens or lengthens the input’s channels. A part of the interval can be preserved or removed. If the channels are being lengthened, the extend conditions of the channel will be used to get the new values.
The handles on the Trim CHOP in the graph can adjust its length.
Determines whether the Start/End parameters are absolute numbers or numbers that are relative to the start and end of the input channels.
The Start or End are the actual numbers defining the new interval.
Relative to Start/End
The Start and End parameters are relative to the start and end of the input CHOP.
Relative to Current Frame
Start and end parameters are computed relative to the current frame.
Current Time Slice
The current time slice is trimmed out.
The start of the range to trim.
The end of the range to trim.
Which part of the channel to discard.
Discard those parts of the channel outside the trim range.
Discard the interior of the trim range. If two intervals remain, sequence them together.
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
Matches each channel that has
foot in it.
? matches a single character.
t? matches two-character channels starting with t.
Matches number ranges giving
[xyz]matches three characters, giving channels
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 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.
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
You can leave the Export Prefix blank, but then your CHOP track names need to be absolute paths, such as
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.
The following examples include this node.
This is an example of how the Extend CHOP determines the values that are computed when sampling outside the interval.
This example demonstrates how to write MIDI data using the MIDI Out CHOP, and read it in using the MIDI In CHOP. The MIDI that is written out is based on geometry, and the MIDI that is read in is controlling other geometry.
This example shows you how to calculate the average speed for each particle over a given time interval using CHOP nodes such as Vector, Trim, and Math.