Houdini 11 Nodes Channel nodes

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

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.