The Constant CHOP creates new constant-value channels. Each channel can be named and assigned a different value. To create a channel, simply enter a channel name in a name parameter on the Constant page, then adjust the below value.
The CHOP interval (length of time) is one sample long by default (one sample at index 0 = frame 1). An interval range can be optionally set in the Channel page.
A simple Constant CHOP with no inputs is the most common use of the CHOP. However, the channels names and values can be set up by connecting any CHOP to its input and clicking the Snapshot Input button (Snap page). This allows you to get some channels from another CHOP and adjust them with sliders in the Constant CHOP.
The second input can be used to add offsets to the constant values. When the second input (Active) is greater than zero, any change to the first input will be added to the output of the CHOP. This is useful for adjusting Constant CHOP values from external input devices like a MIDI slider box. For example you can connect the mouse or a MIDI slider box to a Mouse In CHOP or MIDI In CHOP, and you can raise/lower the Constant CHOP values by holding the Active input On, while moving the mouse or sliders.
Parameters - Constant Page
The channel is created if there is a name in the Name field. You can enter channel name patterns in the Name field, so you can create many channels with the same value. For example, try entering:
Parameters - Snap Page
The Constant CHOP can preset its channel names and values using the Snap page. We often want to grab some channels (Snapshot) and edit them later.
snap - The optional first CHOP input on Constant is used when the Snapshot Input button is pressed. At this time, the channel names and values at the CHOP input at the current frame are used to initialize the channel names and values of the constant sliders.
To snap channels from other OPs, connect a Parameter CHOP to the Constant CHOP and hit
You can simulate the pressing of the Snapshot Input button from a script. To simulate the clicking of a CHOP dialog box button from a script use the Par Class pulse() Method:
first - The First Channel parameter is used to select a smaller set of the incoming channels. This is useful if the number of incoming channels is greater than the 40 channels the Constant CHOP can hold, and you must break it into several CHOPs.
Active Needs Current
current - This is used with the second input as described above, when you want to add a displacement to channels by using external devices or sources.
- When Active Needs Current is On, the second CHOP input (the Active input) has an effect only if the Constant CHOP is the current CHOP.
- When Active Needs Current is Off, the Constant CHOP is affected any time the Active input is on (greater than 0).
- This is used by the Channel Editor when editing keyframes using CHOPs. An input device like a button in the Keyboard In CHOP or a MIDI keyboard can be fed to the Active input of many Constant CHOPs. Only the current CHOP will be affected if this option is On.
Parameters - Channel Page
single - Turn this Off to make constant channels that are longer than one Sample.
start - Start and end of the interval, expressed in Units (seconds, frames or samples). The parameters are expressed in the Units found on the Common page. To set the CHOP to be 100 samples long, Set Units to Samples, Single Frame Off and Start / End to 0 and 99.
startunit - ⊞ -
end - Start and end of the interval, expressed in Units (seconds, frames or samples). The parameters are expressed in the Units found on the Common page. To set the CHOP to be 100 samples long, Set Units to Samples, Single Frame Off and Start / End to 0 and 99.
endunit - ⊞ -
rate - The sample rate of the channels, in samples per second.
left - ⊞ - The left extend conditions (before range).
- Default Value
right - ⊞ - The right extend conditions (after range).
- Default Value
defval - The default value used when one of the Extend parameters is set to Default Value.
Parameters - Common Page
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 - 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.
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
autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.
exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).
- Input 0 -
- Input 1 -
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The term "Frame" is used (1) in the Timeline, (2) as a time-unit in CHOPs, (3) as a time-unit in TOPs, and (4) with movies images which are read and created with TOPs.
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.
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.
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.
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'.