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This CHOP converts channels of all its input chops into binary channels
and combines them using a variety of logic operations.
0 is considered
1 is on.
Result of Channel and CHOP input Operations
Result (Number of Channels in Output)
|Off||Off||Total number of channels in all inputs.|
|Off||On||Number of channels in the first input.|
|On||Off||Same as the number of inputs.|
The method to convert inputs to binary on/off.
Off When Zero
Off When Zero Or Less
negative or zero->0, positive->1
Channel Pre OP
Unary operations can be applied to each channel.
Operation applied between channels within each input.
Operation applied between corresponding channels of multiple inputs.
Channels matched between inputs by number or index.
It is sometimes desirable to produce a warning or an error when channels in the first input fail to be correctly matched to channels in the other inputs. A failure may occur when matching by Channel Number if an input has fewer channels than input 1, or when matching by Channel Name if a channel name cannot be found in input 1.
Inputs that don’t start at same frame can be aligned.
Off To On
The script executed when an output channel switches from off to on, called at the first “on” frame. You can use variables like
$I in the command.
The script executed when an output channel is on. Called once per channel that is on, each frame.
On To Off
The script executed when an output channel switches from on to off, called at the first “off” frame.
The script executed when an output channel is off. Called once per channel that is off, each frame.
Some of these parameters may not be available on all CHOP nodes.
To determine which channels get affected, some CHOPs have a scope string. Patterns can be used in the scope, for example
* (match all), and
? (match single character).
The following are examples of possible channel name matching options:
Matches a single channel name.
chan3 tx ty tz
Matches four channel names, separated by spaces.
Matches each channel that starts with
Matches each channel that has
foot in it.
? matches a single character.
t? matches two-character channels starting with t.
Matches number ranges giving
[xyz]matches three characters, giving channels
Sample Rate Match
The Sample Rate Match Options handle cases where multiple input CHOPs’ sample rates are different.
Resample At First Input’s Rate
Use rate of first input to resample others.
Resample At Maximum Rate
Resample to highest sample rate.
Resample At Minimum Rate
Resample to the lowest sample rate.
Error if Rates Differ
Does not accept conflicting sample rates.
The units for which time parameters are specified.
For example, you can specify the amount of time a lag should last for in seconds (default), frames (at the Houdini FPS), or samples (in the CHOP’s sample rate).
When you change the Units parameter, it does not convert the existing parameters to the new units.
Time Slicing is a feature which boosts cooking performance and reduces memory usage. Traditionally, CHOPs calculate the channel over its entire frame range. If the channel does need to be evaluated every frame, then cooking the entire range of the channel is unnecessary. It is more efficient to calculate only the fraction of the channel that is needed. This fraction is known as a Time Slice.
Causes the memory consumed by a CHOP to be released after it is cooked and the data passed to the next CHOP.
The Export prefix is prepended to CHOP channel names to determine where to export to.
For example, if the CHOP channel was named
geo1:tx, and the prefix was
/obj, the channel would be exported to
You can leave the Export Prefix blank, but then your CHOP track names need to be absolute paths, such as
Every CHOP has this option. Each CHOP gets a default color assigned for display in the Graph port, but you can override the color in the Common page under Graph Color. There are 36 RGB color combinations in the Palette.
Graph Color Step
When the graph displays the animation curves and a CHOP has two or more channels, this defines the difference in color from one channel to the next, giving a rainbow spectrum of colors.
The current value.
The current index.
the current channel (0 to NC-1).
the total number of channels.