Math CHOP

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Summary
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The Math CHOP performs arithmetic operations on channels. The channels of a CHOP can be combined into one channel, and several CHOPs can be combined into one CHOP.

The OP page lets you pre-operate on each sample, like making all samples positive or taking the square of each sample.

Using Combine Channels, for an input CHOP with multi-channels, you can multiply the samples of one channel by the samples in the other channels, reducing N channels down to one. You can combine them by multiplying, adding, finding the maximum, etc..

Using Combine CHOPs, where there are two or more CHOP inputs, you can multiply (or add, etc.) the channels in one CHOP with the channels in all the other CHOPs, reducing N CHOPs to 1. (otherwise channels of multi-inputs are just merged)

You can then post-operate on the resulting samples - negate, square root, etc.

Then using the Mult-Add page it can offset and scale the values of each sample.

More conveniently you can use the Range page to do linear scaling as well by setting an output low-high range for a certain input low-high range.

Finally, you can round the resulting values off to an integer.

NOTE: To do logic operations (and, or, ...) between channels or CHOPs, use the Logic CHOP.

PythonIcon.pngmathCHOP_Class


Parameters - OP Page

The four steps are performed in the following order:

Channel Pre OP preop - - Unary operations can be performed on individual channels. A menu of unary operations (as described above) that are performed on each channel as it comes in to the Math CHOP include:

  • Off off - Don't do anything to the channel.
  • Negate negate - Take the negative value of each sample of the channel.
  • Positive pos - Make negative values of the channel positive (absolute).
  • Root root - Take the square root of all values in the channel.
  • Square square - Square all the values in the channel.
  • Inverse inverse - Take the inverse (1/x) of all values in the channel.

Combine Channels chanop - - A choice of operations is performed between the channels of an input CHOP, for each input. The Nth sample of one channel is combined with the Nth sample of other channels:

  • Off off - Don't combine the channels.
  • Add add - Sum all the channels.
  • Subtract sub - Subtract all the channels from the first.
  • Multiply mul - Multiply all the channels.
  • Divide div - Divide the first channel by all the rest.
  • Average avg - Take the average of all the channels.
  • Minimum min - Take the minimum value of all the channels.
  • Maximum max - Take the maximum value of all the channels.
  • Length len - Assume the channels are a vector and compute its length.

Combine CHOPs chopop - - A menu of operations that is performed between the input CHOPs, combining several CHOPs into one.

  • Off off - Don't combine the channels.
  • Add add - Sum all the channels.
  • Subtract sub - Subtract all the channels from the first.
  • Multiply mul - Multiply of all the channels.
  • Divide div - Divide the first channel by all the rest.
  • Average avg - Take the average of all the channels.
  • Minimum min - Take the minimum value of all the channels.
  • Maximum max - Take the maximum value of all the channels.
  • Length len - Assume the channels are a vector and compute its length.

Channel Post OP postop - - A menu (same as Channel Pre OP) is performed as the finale stage upon the channels resulting from the above operations.

  • Off off -
  • Negate negate -
  • Positive pos -
  • Root root -
  • Square square -
  • Inverse inverse -

Integer integer - - The resulting values can be converted to integer.

  • Off off - Don't affect the value.
  • Ceiling ceiling - Round a value up to the next integer.
  • Floor floor - Round a value down to the next integer.
  • Round round - Round a value to the nearest integer.

Match by match - - Match channels between inputs by name or index.

  • Channel Number index -
  • Channel Name name -

Align align - - This menu handles cases where multiple input CHOPs have different start or end times. All channels output from a CHOP share the same start/end interval, so the inputs must be treated with the Align Options:

  • Automatic auto - It will trim to the current Time Slice if there are any Time Slices, else it will do an Extend Min/Max.
  • Extend to Min/Max none - Find the earliest start and latest end, and extend all inputs to that range using the extend conditions. (see Extend Conditions).
  • Stretch to Min/Max stretch - Find the earliest start and latest end, and stretch every channel's start and end to that range.
  • Shift to Minimum start - Find the earliest start and shift all channels so they all start at that index. All channels are extended to the length of the longest one.
  • Shift to Maximum end - Find the latest end and shift all channels so they all end at that index. Extend all channels to the length of the longest one.
  • Shift to First Interval shift1 - Shift all channels to the start of the first CHOP and sample all inputs using the first input's range.
  • Trim to First Interval trim1 - Trim all channels to first CHOP's range.
  • Stretch to First Interval stretch1 - Stretch all channels to the first CHOP's range.
  • Trim to Smallest Interval trim - Trim all channels to the smallest start/end interval. The start and end values may not come from the same channel.
  • Stretch to Smallest Interval squash - Stretch all channels to the smallest start/end interval. The start and end values may not come from the same channel.


Parameters - Mult-Add Page

The three steps are next performed in the following order:

Pre-Add preoff - First, add the value to each sample of each channel.  

Multiply gain - Then multiply by this value.  

Post-Add postoff - Then add this value.  


Parameters - Range Page

This is the final step prior to output.

From Range fromrange - - Another way to multiply/add. Converts from one low-high range to another range.

  • fromrange1 -
  • fromrange2 -

To Range torange - - Another way to multiply/add. Converts from one low-high range to another range.

  • torange1 -
  • torange2 -


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 -

TouchDesigner Build:

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.

Any of the procedural data operators. OPs do all the work in TouchDesigner. They "cook" and output data to other OPs, which ultimately result in new images, data and audio being generated. See Node.

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.

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'.