This CHOP allows you to edit the channel data by using direct manipulation of cubic or Bezier handles in the graph of the CHOP.
The CHOP first does a best-fit on the existing samples based on the Tolerance, the Start-End range and the channel Scope.
The CHOP’s entire interval or a sub-interval can be edited. The scope can be used to limit which channels are to be edited. Changing the scope causes any prior hand-edits to be lost.
In the graph, the solid boxes at the ends of the chop interval can be moved to shorten the interval to be edited.
The hollow boxes are the handles for editing the interpolation curves. As soon as one of these is moved, the start-end handles or scope cannot be changed without losing the hand-edits. To change the interval or re-edit the curves, turn on Compute Knots again. You can shorten the edit interval to one sample and edit a single sample.
The type of fitting curves to use, Bezier or Cubic.
Turn this on to recompute the knots when you modify the error or the start or end of the subrange. All previous changes to the knots will be erased. Any change to a knot will turn this parameter off.
Determines whether the start/end parameters listed below are absolute values or relative to the start and end of the channels.
The start of the subrange.
The end of the subrange.
The error tolerance when fitting curves to the data. Lower error tolerances produce a more accurate reconstruction of the original data, but may use more curve segments.
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.