Slope CHOP

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Summary

The Slope CHOP calculates the slope (or "derivative" in math-speak) of the input channels.

If the input CHOP represents position, the slope can be interpreted as speed. By default, the Slope CHOP converts position to speed.

In mathematical terms, the slope is the first derivative of the channel curve. The second and third derivatives can also be calculated. The second derivative can be interpreted as acceleration (and the third derivative could be interpreted as the rate of change in acceleration).

This CHOP can be used in conjunction with the Speed CHOP to manipulate speed or acceleration directly. You can calculate the speed or acceleration of a moving object with a Slope CHOP and manipulate it with other CHOPs. Then you can convert the new speed or acceleration curve back to position data with a Speed CHOP. You may need to adjust the starting position, since the Slope CHOP removes this information. This can be done with the use of the Constant parameters in the Speed CHOP.

The Units option causes the output to be expressed as a change in value per sample, value per frame, or value per second.

PythonIcon.pngslopeCHOP_Class


Parameters - Slope Page

Type type - - The type of slope to calculate.

  • Slope slope - Calculates the slope of the channels.
  • Acceleration accel - Calculates the acceleration of the channels.
  • Acceleration Of Slope slacc - Calculates the acceleration of the slopes of the channels.

Method method - - The sample pairs used to calculate the slope.

  • Use Previous And Current Sample pc - The current sample and the sample before it are used. This is the only method applicable in realtime applications.
  • Use Current And Next Sample cn - The current and the next samples are used.
  • Use Previous And Next Sample pn - The previous and the next samples are used, producing slightly more continuous slopes than the other methods.

The slope at a sample is calculated by looking at the values of samples just before, at, and after it.

For the Slope Type, it needs two values, and the options are given to use three combinations, the default being to use the value at the sample and the one before. (before - current) is divided by the time between the samples (determined by the sampling rate). The slope placed in the channel is expressed in the Units of the CHOP.

For the type Acceleration, it uses three consecutive samples around the sample it is computing. The most accurate acceleration is obtained with Use Previous and Next Sample.



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).



CHOPs
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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 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.