Trigger channel node

Adds an audio-style attack/decay/sustain/release (ADSR) envelope to all trigger points in the input channels.

All

Parameters

Local variables

See also: Count, Hold

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 0.

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.

Parameters

Trigger

Release = Trigger Threshold	If on, the trigger and release thresholds are the same value.
Trigger Threshold	The trigger threshold (see above)
Release Threshold	The release threshold (see above)
Re-trigger Delay	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.
Trigger On	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.

Attack

Delay Length	The amount of time to delay the envelope after the trigger point.
Attack Length	The amount of rise time from zero to the peak level.
Attack Shape	The shape of the attack ramp.
Peak Level	The peak level.
Peak Length	The length of time of the peak.

Sustain

Decay Length	The amount of decay time from the peak level to the sustain level.
Decay Shape	The shape of the decay ramp.
Sustain Level	The sustain level. This level is held until a release point is reached.
Release Length	The amount of release time from the sustain level to zero.
Release Shape	The shape of the release ramp.

Chan

Channel Name

Channel name when no inputs connected.

Sample Rate

Sample rate when no inputs connected.

Complete Envelope

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.

Remainder

What to do with remaining samples at end of the interval.

Discard Remainder	Output interval = input interval.
Make Output Longer	Output longer if envelope unfinished.
Mix Remainder to Beginning	Add remainder to samples at the start.

Common

Some of these parameters may not be avaiable on all CHOP nodes.

Scope

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:

`chan2`	Matches a single channel name.
`chan3 tx ty tz`	Matches four channel names, separated by spaces.
`chan*`	Matches each channel that starts with `chan`.
`foot`	Matches each channel that has `foot` in it.
`t?`	The `?` matches a single character. `t?` matches two-character channels starting with t.
`r[xyz]`	Matches channels `rx`, `ry` and `rz`.
`blend[3-7:2]`	Matches number ranges giving `blend3`, `blend5`, and `blend7`.
`blend[2-3,5,13]`	Matches channels `blend2`, `blend3`, `blend5`, `blend13`.
`t[xyz]`	`[xyz]`matches three characters, giving channels `tx`, `ty` and `tz`.

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.

Units

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).

Note

When you change the Units parameter, it does not convert the existing parameters to the new units.

Time Slice

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.

Unload

Causes the memory consumed by a CHOP to be released after it is cooked and the data passed to the next CHOP.

Export Prefix

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 /obj/geo1/tx.

Note

You can leave the Export Prefix blank, but then your CHOP track names need to be absolute paths, such as obj:geo1:tx.

Graph Color

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.

Local variables

C	The current channel (0 to NC-1).
NC	The total number of channels.

Usages in other examples

Example name	Example for
Lookup	Lookup channel node	Load \| Launch