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This CHOP adds an audio-style attack/decay/sustain/release (ADSR) envelope to all trigger points in the input channels. A trigger point occurs whenever the first input’s channel increases across the trigger threshold value.
The envelope consists of six major sections: delay, attack, peak, decay, sustain and release.
From the time the threshold is reached and while the channel’s value is above the release threshold, the envelope is in its sustain phase during which it will delay, attack, peak-hold, decay and then maintain its sustain value. Then the envelope will decay to
The peak and sustain levels can be set independently, but peak can never be less than sustain.
Without an input connected, a single full envelope is generated.
Release = Trigger Threshold
If on, the trigger and release thresholds are the same value.
The trigger threshold (see above)
The release threshold (see above)
The amount of time after a trigger point that a new trigger may occur.
Min Trigger Length
The minimum amount of time that the trigger will remain active.
Determines whether a trigger occurs on an increasing slope or decreasing slope when passing the trigger threshold. A release will occur on the opposite slope.
The amount of time to delay the envelope after the trigger point.
The amount of rise time from zero to the peak level.
The shape of the attack ramp.
The peak level.
The length of time of the peak.
The amount of decay time from the peak level to the sustain level.
The shape of the decay ramp.
The sustain level. This level is held until a release point is reached.
The amount of release time from the sustain level to zero.
The shape of the release ramp.
Channel name when no inputs connected.
Sample rate when no inputs connected.
If on, a complete envelope is produced for each trigger point. If off, the envelope may be terminated at any time by a release point.
What to do with remaining samples at end of the interval.
Output interval = input interval.
Make Output Longer
Output longer if envelope unfinished.
Mix Remainder to Beginning
Add remainder to samples at the start.
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.