The Lookup CHOP outputs values from a lookup table. The first input (the Index Channel) is an index into the second input (the Lookup Table). Lookup outputs interpolated values from the lookup table.
Both the Index and Lookup Tables can contain any number of channels.
An Index sample with value 0 maps to the beginning (first sample) of the lookup table, and an index sample with value of 1 maps to the end (last sample) of the lookup table.
The output CHOP is the same length as the Index input. It is the same number of channels as the Lookup Table input, and has the same channel names as the Lookup Table input. The output is filled with the data extracted from the lookup tables. Indexes that fall between two lookup table samples are interpolated. The lookup table can be sampled outside its range. The Extend Conditions of the lookup table are used in this case where the index is less than 0 or greater than 1.
The sample rate of the output is the sample rate of the Index input.
The Lookup CHOP can be used to fetch values from a color lookup table, where a single index produces red, green and blue channels. It can also be used for rolloff or decay tables, where it specifies how much a parameter drops with distance.
Parameters - Lookup Page
index- ▶ - The Index Range maps the index channel's values to the lookup table's start and end and defaults to 0 and 1. The first parameter represents the start of the lookup table. When the index channel has this value, it will index the start of the lookup table. The second parameter represents the end of the lookup table and behaves in the same way.
cyclic - ⊞ - Adapts the range of the Lookup Table (2nd input) for cyclic or non-cyclic input indices. When using a cyclic input index (1st input), the lookup value for index 0.0 and 1.0 result in the same value. To avoid this, set Cyclic Range to Yes and the lookup will cycle smoothly.
auto- Checks the right extend condition of each channel (Assumes type cycle and mirror are cyclic lookups).
yes- For looking up a cyclic output (oscillator, beat driven output etc).
no- For looking up a single wave (slider mapping, etc).
Per Index Channel
chanmatch - ⊞ - Determines how index channels are mapped to lookup Channel tables.
- One Lookup Table Channel
onetoone- The first index channel is matched to the full lookup table.
- All Lookup Table Channels
onetomany- Each index channel is matched with every lookup table.
match - ⊞ - Determines how index channels are matched with a lookup channel in 'One Lookup Table Channel' mode.
- Channel Number
index- An index channel is matched to a lookup table by its index within the clip. Lookup tables are cycled if there are few of them than index channels.
- Channel Name
name- An index channel is matched to a lookup table by name. Unmatched index channels are left "as is".
interp - When on, the input can be interpolated between samples. When off, the nearest sample is used.
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).
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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.
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'.