# Spring CHOP

## Summary

The Spring CHOP creates vibrations influenced by the input channels, as if a mass was attached to a spring.

It acts as if, for every channel, there is a mass at the end of a spring, affected by a distance from the actual position (the output of the channel at the previous frame) to the desired position (the input channel at the current frame). When the distance (output - input) is zero, there is no force and therefore no movement.

Alternately, when Input Effect is force, the input is used as a force on the spring/mass, and the CHOP reacts to this force plus the force of the spring/mass. In this case, the mass would always stabilize at value 0 if the input is a force of 0.

The damping acts to make the spring system lose energy, so that higher damping makes everything come to rest sooner.

Its behavior is best understood by feeding it a chop that steps from one constant value to another in sequence, then playing with the constants.

## Parameters - Spring Page

Spring Constant `springk` - The strength of the spring. Larger spring constants produce higher frequency oscillations.

Mass `mass` - The mass of the object on the end of the spring. Higher masses will produce lower frequency oscillations, have higher amplitudes, and be more resistant to damping.

Damping Constant `dampingk` - The amount of damping (resistance) applied to the spring action. Higher damping causes oscillations to die off more quickly.

Input Effect `method` - - Determines whether the input channel(s) represents a position or a force.

• Position `disp` -
• Force `force` -

Intial Conditions from Channel `condfromchan` - If On, the initial position and velocity are calculated from the values at the beginning of the channel.

Initial Position `initpos` - The initial position of the mass attached to the spring.

Initial Speed `initspeed` - The initial velocity of the mass attached to the spring.

Intial Conditions from Channel `condfromchan` - If On, the initial position and velocity are calculated from the values at the beginning of the channel.

Reset `reset` - While On resets the spring effect of the CHOP.

Reset Pulse `resetpulse` - Instantly reset the spring effect.

## 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).

## Operator Inputs

• Input 0 -

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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.

A CHOP outputs one or more channels, where a channel is simply a sequence of numbers, representing motion, audio, etc. Channels are passed between CHOPs in TouchDesigner networks. See also Export.

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 via python is via the `.pulse()` function on a pulse-type parameter, such as Reset in a Speed CHOP. A pulse from a CHOP is typically a 0 to 1 to 0 signal in a channel.

A Time Slice is the time from the last cook frame to the current cook frame. In CHOPs it is the 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.

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.

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`.