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This CHOP preserves the shape of channels and the sampling rate, but resamples the channels into a new interval. All data in the range is stretched or compressed to the new start and end positions.
The interpolation method to use when resampling.
Use the value of the nearest sample.
Use linear interpolation between samples if CHOP is being lengthened. Averages all samples near the new sample if CHOP is being shortened.
Cubically interpolates between samples, for smoother curves than Linear. This method is not recommended for channels with sharp changes.
A linear interpolation that recognizes single sample pulses and preserves their height and one sample width. A pulse is a non-zero value preceded and followed by zero-value samples.
If on, keeps the area under the channel constant by scaling the the values of the channel.
Determines how Start/End parameters are interpreted.
The value is the new start/end position.
Relative to Start/End
The value is a shift from the old start/end position.
The CHOP’s new start position.
The CHOP’s new end position.
Scales the length of the channel after determining the start/end interval. Good for doubling or halving the length.
Reverses the channel so that it plays backwards.
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 current channel (0 to NC-1).
The total number of channels.
This example demonstrates how the Stretch CHOP changes the Start and/or End interval. It then resamples the input channel, preserving the shape of the channel. The sample rate remains the same, however, the interval changes.
The following examples include this node.