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This CHOP produces multiple copies of the second input along the timeline of the first input. The first input provides the trigger signals or the convolve levels.
The Copy CHOP can be used to produce a motion every time a trigger occurs. It can be used to trigger motion, such as eyelid blinks. The copies it produces can be identical, or the copies can be re-cooked each time a copy is added to the timeline. It is useful for triggering a sound multiple times, where the sounds may overlap in time.
Each copy that is added to the output can be completely different than any other copy. By passing variables through the Variables page, the second (Copy) input can be any chop chain that uses the variables and recooks to create each copy.
Method used for the copy operation.
The second input is copied (convolved) over the first input’s trigger points only. A trigger point occurs whenever the first input’s channel crosses the Trigger Threshold value. Overlapping copies are added.
For every sample in the first input’s channel, the second input is shifted to that point in time, scaled by the sample value, and added into the output channels.
How to output the channels
One Channel Per Template Channel
Each output channel is a channel from the first input combined with the corresponding channel from the second input.
One Channel Per Copy Channel
Each output channel is a channel from the second input, with copies triggered by every channel of the first input.
The threshold value for triggering copies.
What to do with remaining samples at end of the interval.
Output interval = input interval.
Make Output Longer
Output is longer if envelope unfinished.
Mix Remainder to Beginning
Add remainder to samples at the start.
Keep Non-Scoped Channels
If on, non-scoped channels are copied to the output, otherwise they are deleted.
Cook Each Copy
Recook the second input for each triggered copy.
The parameters are re-calculated for each copy. The first field is the parameter name, the second is its value. You can use local variables and the ic() functions. The parameters you set here are available to any CHOP in the network attached to the second input through function param(“name”, initval), where initval is any initial value for the parameter, usually set to 0.
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.
The current index.
The current channel (0 to NC-1).
The total number of channels.
The value at the current index of the current channel.
The copy number. (The first thing it copies is 0.)
This file demonstrates how the Copy CHOP can be used to copy channels and apply them to geometry.
This example demonstrates how the Copy CHOP additively copies the values of a channel onto the time line of another to create a new channel.
This example demonstrates how to use the CopyStamp feature of the Copy CHOP. Custom variables are created within the Copy CHOP and used to modify the geometry.
In the file, geometry is imported into CHOPS. The Alpha attribute is scoped and manipulated using the Copy Stamping technique.
The new Alpha data is then brought back to the SOP level, and applied to the geometry’s Position.