Sequence channel node

Takes all its inputs and appends one chop after another.

All Parameters Example files

See also: Blend, Composite

This CHOP takes all its inputs and appends one CHOP after another. It is expected they all have the same channels.

The end section of the first CHOP is overlapped with the start section of the second CHOP, and so on for the rest of the input CHOPs. The second input is shifted to line up with the end of the first.

Blending allows you to splice channels together by slowly phasing out one CHOP while phasing into the next, or by inserting interpolation curves between the channels of the adjacent chops.

Quaternion Blend blends rotation triplets (rx ry rz) together using the shortest rotation arc. Rotation triplets are identified by “quaternion” attributes, which are set in the Attribute CHOP.

Translation Blending blends translation channels together by slowly changing from the final velocity of the previous channel to the initial velocity of the next. The next channel may be shifted up or down. If this is undesirable, use cubic blending instead (in the Shape menu). Translation Blending is done on channel triplets that represent translations or positions (*tx *ty *tz).

Parameters

Blend

Method

The blend method to use to produce a seamless sequence.

Preserve Length

Keeps the total length of the channel constant.

Overlap Sequences

Overlaps the current cycle with the last cycle. Audio sequences should always use this method.

Insert Blend Region

Inserts a region between the cycles where the blending is done.

Shape

Blend interpolation shape. See Cycle CHOP.

Region

The size of the blend region.

Bias

Which segment to favor when blending: the previous (-1), the next (+1) or none (0).

Match By

Match channels between inputs by index or by name.

Scope

Step

If set to 1, the next segment will be shifted up or down so that it begins where the last segment ended.

Step Scope

The names of channels that use the Step function.

Blend Scope

The names of the channels that should be blended. Other channels will not be blended at all.

Translate Blend

The names of channels that will be translation-blended. Each string field contains a list of its component channels, such as x, y or z.

Rotate

Quaternion Blend

Use quaternion blending on rotation channels.

Shortest Path Rotation Blending

If on, compensate for cyclic channels (such as angles) by always choosing the shortest route between samples when blending.

Rotation Scope

Defines which channels are rotations for Shortest Path Rotation Blending.

Cycle Length

The length of the cycle for Shortest Path Rotation Blending.

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.

Example files

Sequence

$HFS/houdini/help/examples/nodes/chop/sequence/Sequence.cmd

Load | Launch

The Sequence CHOP is used to combine multiple waves into a single wave.

This CHOP takes all its input CHOPs and appends one wave after another. It is expected the input CHOPs all have the same channels.

The end section of the first CHOP is overlapped with the start section of the second CHOP, and so on for the rest of the input CHOPs. The second input is shifted to line up with the end of the first.

To visualize the channels in this demonstration, please enter the CHOP network.

Usages in other examples

Example name Example for