Interpolate channel node

Treats its multiple-inputs as keyframes and interpolates between them.

All

Parameters

Example files

See also: Blend

This CHOP treats its multiple-inputs as keyframes and interpolates between them. The inputs are usually single-frame CHOPs like those produced by a Constant CHOP. The Interpolate CHOP first sorts the input CHOPs in time (without shifting them) and interpolates between them to fill the gaps.

The number of channels in the output is the same as the number of channels in the first input.

If a channel is missing in an input, and Match By is set to Name, it is treated as if there is no keyframe at that frame for that channel, and the interpolation occurs between CHOPs before and after that frame.

When the graph is displayed as timebars, and you click on the black lines of the Interpolate CHOP time bar which represent the inputs of the CHOP, you can drag the line to change the time of that input. It goes to that input and changes the value if its “start” parameter, so you can re-time the keyframes.

When you Shift-click on a black line, the current CHOP changes to the corresponding input, so you can edit its values.

This CHOP has Sample Rate Match options in the Common page.

Parameters

Interpolate

Shape

The shape of the interpolation curve.

Linear	A straight line.
Ease In	Exponential rise.
Ease Out	Exponential fall.
Ease In Ease Out	Half cosine blend.
Cubic	A cubic spline.
Add	Overlapping parts, if any, are added.

Overlap Priority

If an input is not a single frame, and if there are overlaps in the input CHOPs, an option is used to resolve the conflict.

First Segment has Priority	Use the segment with the earliest start time.
Last Segment has Priority	Use the segment with the latest start time.
Average Overlap	Combine the conflicting channels by averaging them.

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

InterpolateBasic

$HFS/houdini/help/examples/nodes/chop/interp/InterpolateBasic.cmd

Load | Launch

This example file uses the Interpolate CHOP to read in multiple frames.

These Key Frames are interpolated to create a new Channel. Different settings in the Interpolate CHOP can creat curves, such a cubic, linear, ease, and so on.

Usages in other examples

Example name	Example for
Blend	Blend channel node	Load \| Launch