This CHOP time-warps the channels of the first input (the Pre-Warp Channels) using one warping channel in the second input (the Warp Curve). The Warp Curve acts as either a rate control or an index control, as explained below.
In the Rate Control Method, feeding the Warp CHOP a Warp Curve with a
constant value of
1 makes the output identical to the Pre-Warp Channels,
assuming the two inputs have the same start-end interval. That is, where
the rate is
1, the Pre-Warp Channels are not warped.
Where the Warp Curve is above
1, it causes a speed-up in the animation.
Where the Warp Curve is below
1, it causes a slow-down in the animation.
Rates less than
0 cause the animation to go in reverse.
In the Index Control Method, the Warp Curve acts as an index into the
first input. If the Warp Curve is a straight ramp with a slope of
Units), it produces unwarped output channels. If Units is set to
Seconds, a Warp Curve value of
0 gets the Pre-Warp Channels' values at
time 0 seconds. A Warp Curve value of
2 gets the Pre-Warp Channels'
values at time 2 seconds.
The Warp CHOP will output the same number of channels and channel names as the Pre-Warp Channels input, and the sample rate will be the same as that of the Pre-Warp input. However, the CHOP will output the same start-end time interval as the Warp Curve input.
If you take a Warp Curve and pass it directly to a Warp CHOP with the Rate Control Method, it is equivalent to passing the same curve to an Area CHOP and then passing it to the Warp CHOP with the Index Control Method.
The warping method to use, Rate or Index Control
Stretch Indices To Channel Length
If on, the minimum and maximum values in the Warp Curve are mapped to the beginning and end of the channels to be warped.
Otherwise, the Warp Curve is applied “as-is” to the Pre-Warp Channels.
Some of these parameters may not be available on all CHOP nodes.
To determine the channels that are affected, some CHOPs have a scope string. Patterns can be used in 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 the rate of the first input to resample the others.
Resample At Maximum Rate
Resample to the 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 of the time parameters.
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, the existing parameters are not converted to the new units.
Time slicing is a feature that boosts cooking performance and reduces memory usage. Traditionally, CHOPs calculate the channel over its entire frame range. If the channel needs 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 the 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 to it for display in the graph, but you can override the color with the 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.