Event CHOP

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The Event CHOP manages the birth and life of overlapping events triggered by devices like a MIDI keyboard. It can be seen as a simple particle system designed for MIDI keyboards.

The Event CHOP generates one sample for each off-to-on event in the input channels, which would often come from a MIDI In CHOP, MIDI In Map CHOP, Keyboard In CHOP, or python events sent to the Event CHOP. The sample exists for the duration of the event's attack+decay+sustain+release time.

NOTE: See the examples in Help->OP Snippets

The Event CHOP can used to follow a polyphonic music keyboard with MIDI velocity, and can generate generating one object, polygon or geometry instance for each event. It assures the object, polygon or instance exists until the event ends after an attack-decay-sustain-release phase. The Event CHOP is often fed through other OPs to the Instance parameters of a Geometry component.

The Event CHOP outputs up to 8 channels, with one sample generated per off-to-on event that is active. The sample is active until the attack-decay-sustain-release is over, at which moment the sample disappears (like particle death).

Watch the channel graph of the Event CHOP to understand what it is doing. It can be sent to a Limit SOP or a Channel SOP to place geometry for each event. You can send event information to the SOP via the Event CHOP channels that get transformed into geometry channels like tx, ty, scale, texture v (giving movie time offsets), alpha, r, g and b colors.

On a MIDI keyboard, you can trigger many events simultaneously, and, like particles, you may want to launch objects that remain in existence the next time you press the same key.

The Event CHOP is designed to handle this. It creates one sample every time you press any key, and that sample lives for any length of time. This CHOP is lightweight - the minimum number of channels and samples are created, even with 88-key MIDI keyboards and lots of pounding on the keyboard.

There are channels that represent age, note number and MIDI velocity when you pressed the key, as well as a flag telling if the key has since been released.

Each event has a unique ID, held in the id channel that can be used to generate random XY displacements of each note, for example.

A movie index is set by the state channel which rises from 0 to 1 and loops between 1 to 2 continuously until the note goes into its release state at which time it goes from 2 to 3. So for a bird cycle, you use the 0 to 1 state for the jump phase, 1 to 2 for the flappin in flight phase, and 2 to 3 for the landing phase.

The Event CHOP's 1st input is for event triggers.

The 2nd input resets the triggers.

The 3rd input is optional and allows for sampling values for each event.

See also: Timer CHOP, Count CHOP, Speed CHOP, Trigger CHOP


Parameters - Channels Page

The Event CHOP outputs seven channels that define the properties of the events.

ID id - The sequence # of the event, starting from 0 and incrementing by 1 for each event.

Index index - The channel index of the incoming CHOP that caused the event.

Active active -

Input input - The value of the input channel when the input went on (at the birth of the event). It is often the note velocity value. If you pass the Midi In CHOP into the Event CHOP, and set the Midi In option to output the velocity, velocity will end up in this channel and preserved until the event ends.

Time time - Time in seconds from the start of the event.

ADSR adsr - The value according to the Attack, Decay, Sustain, Release. It uses the parameters on the ADSR page, regulating the speed and values, with extended parameters: Attack Time, Attack Level, Decay Time, Sustain Time, Sustain Min, Sustain Max, Release Time, Release Level.

State state - This is good for playing back movies. You divide your movie into 4 parts that correspond to the (0=attack, 1=decay, 2=sustain, 3=release) phases. The state channel outputs fractional values, so you can watch it climb through all the transitions, including multiple sustain-sections. e.g., 0...1...2...2...2...2...3...4. If your movie is 8 seconds long, take the state channel and multiply by 2, passing it as the time-index of the movie. Goes from 0 to 1 during the attack phase, 1 to 2 as it repeats in the sustain phase, and 2 to 3 in the release phase. It is suitable for indexing movies.

Reset Condition resetcondition - - Determines the reset behavior of using the 2nd Input Reset Trigger. This parameter is only active if there is an input connected to the CHOP's 2nd input.

  • Off to On offtoon -
  • While On on -
  • On to Off ontooff -
  • While Off off -

Reset reset - Resets the CHOP clearing all events.

Reset Pulse resetpulse -

Callbacks DAT callbacks -

Parameters - ADSR Page

Attack Time attacktime - Affects adsr and state channel. Time to rise to max attack level.  

Attack Time Unit attacktunit - -

Attack Level attacklevel - Affects adsr channel. Peak attack level.  

Decay Time decaytime - Affects adsr channel and state channel. Time after peak to sustain level.  

Decay Time Unit decaytunit - -

Sustain Time sustaintime - Affects adsr channel.  

Sustain Time Unit sustaintunit - -

Sustain Min sustainmin - Affects adsr channel. Level at start of sustain time.  

Sustain Max sustainmax - Affects adsr channel. Level at end of sustain time.  

Release Time releasetime - Affects adsr and state channels.  

Release Time Unit releasetunit - -

Release Level releaselevel - Affects adsr channel. Level at end of life cycle.  

Speed speed - Affects the speed of the event, letting you stretch out or shorten the life of an event.  

Global Speed globalspeed -  

Parameters - Common Page

Time Slice timeslice - Turning this on forces the channels to be "Time Sliced". A Time Slice is the time between the last cook frame and the current cook frame.

Scope scope - To determine which channels get affected, some CHOPs use a Scope string on the Common page.

Sample Rate Match srselect - - Handle cases where multiple input CHOPs' sample rates are different. When Resampling occurs, the curves are interpolated according to the Interpolation Method Option, or "Linear" if the Interpolate Options are not available.

  • Resample At First Input's Rate first - Use rate of first input to resample others.
  • Resample At Maximum Rate max - Resample to the highest sample rate.
  • Resample At Minimum Rate min - Resample to the lowest sample rate.
  • Error If Rates Differ err - Doesn't accept conflicting sample rates.

Export Method exportmethod - - This will determine how to connect the CHOP channel to the parameter. Refer to the Export article for more information.

  • DAT Table by Index datindex - Uses the docked DAT table and references the channel via the index of the channel in the CHOP.
  • DAT Table by Name datname - Uses the docked DAT table and references the channel via the name of the channel in the CHOP.
  • Channel Name is Path:Parameter autoname - The channel is the full destination of where to export to, such has geo1/transform1:tx.

Export Root autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.

Export Table exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).

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An Operator Family which operate on Channels (a series of numbers) which are used for animation, audio, mathematics, simulation, logic, UI construction, and many other applications.

(1) A Geometry Component can render its SOP geometry many times using CHOP samples, (2) an OP that doesn't actually have its own data, but rather just refers to an OP (or has an input) whose data it uses. This includes Null OPs, Select OPs and Switch OPs.

An Operator Family that reads, creates and modifies 3D polygons, curves, NURBS surfaces, spheres, meatballs and other 3D surface data.

To pulse a parameter is to send it a signal from a CHOP or python or a mouse click that causes a new action to occur immediately. A pulse from a CHOP is typically a 0 to 1 to 0 signal in a channel, and a pulse via python is via a .pulse() call on a pulse-type parameter, such as Reset in a Speed CHOP.

An Operator Family that manipulates text strings: multi-line text or tables. Multi-line text is often a command Script, but can be any multi-line text. Tables are rows and columns of cells, each containing a text string.

A Time Slice is the time between the last cook frame and the current cook frame. In CHOPs it is a set of short channels that only contain the CHOP channels' samples between the last and the current cook frame.

A parameter in most CHOPs that restricts which channels of that CHOP will be affected. Normally all channels of a CHOP are affected by the operator.

samples-per-second of a CHOP. Each CHOP in your network has a sample rate, whether it is used or not. The overall timeline has a "frame rate", which is the number of animation frames per second, generally your monitor display frequency.

Exporting is the connection of CHOP channels to parameters of operators. The output of each exporting CHOP is one or more channels, active only while the CHOP Viewer is on. The current value of a channel can be exported to a parameter of any operator, overriding that parameter's value. See Parameter.

The location of an operator within the TouchDesigner environment, for example, /geo1/torus1, a node called torus1 in a component called geo1. The path / is called Root. To refer instead to a filesystem folder, directory, disk file or http: address, see Folder.

Parameters in TouchDesigner are an operator's settings (numbers, menus, flags, strings, paths) which the user can alter. Parameters for any operator can be opened by right-clicking on the operator and selecting "Parameters..." A currently selected operator's parameters can be viewed in a Network Editor by pressing the keyboard shortcut 'p'.

TouchDesigner is a hierarchy of components. "root" is the top-most network in the hierarchy. The Path is simply /. A typical path is /project1/moviein1.