Logic channel node

Converts channels of all its input chops into binary channels and combines them using a…

All

Parameters

Local variables

This CHOP converts channels of all its input chops into binary channels and combines them using a variety of logic operations. 0 is considered off, and 1 is on.

Result of Channel and CHOP input Operations

Combine Channels	Combine CHOPs	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.
On	On	One channel.

Parameters

Logic

Convert Input

The method to convert inputs to binary on/off.

Off When Zero	zero->0, non-zero->1
Off When Zero Or Less	negative or zero->0, positive->1

Channel Pre OP

Unary operations can be applied to each channel.

Combine Channels

Operation applied between channels within each input.

Combine CHOPs

Operation applied between corresponding channels of multiple inputs.

Match By

Channels matched between inputs by number or index.

Align

Inputs that don’t start at same frame can be aligned.

Script

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 $C and $I in the command.
While On	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.
While Off	The script executed when an output channel is off. Called once per channel that is off, each frame.

Common

Some of these parameters may not be avaiable on all CHOP nodes.

Scope

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:

`chan2`	Matches a single channel name.
`chan3 tx ty tz`	Matches four channel names, separated by spaces.
`chan*`	Matches each channel that starts with `chan`.
`foot`	Matches each channel that has `foot` in it.
`t?`	The `?` matches a single character. `t?` matches two-character channels starting with t.
`r[xyz]`	Matches channels `rx`, `ry` and `rz`.
`blend[3-7:2]`	Matches number ranges giving `blend3`, `blend5`, and `blend7`.
`blend[2-3,5,13]`	Matches channels `blend2`, `blend3`, `blend5`, `blend13`.
`t[xyz]`	`[xyz]`matches three characters, giving channels `tx`, `ty` and `tz`.

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.

Units

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).

Note

When you change the Units parameter, it does not convert the existing parameters to the new units.

Time Slice

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.

Unload

Causes the memory consumed by a CHOP to be released after it is cooked and the data passed to the next CHOP.

Export Prefix

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 /obj/geo1/tx.

Note

You can leave the Export Prefix blank, but then your CHOP track names need to be absolute paths, such as obj:geo1:tx.

Graph Color

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.

Local variables

V	The current value.
I	The current index.
C, NC	The current channel (0 to NC-1), the total number of channels.

Usages in other examples

Example name	Example for