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This CHOP layers (blends) the channels of one CHOP on the channels of another CHOP. The first input is the base input and the second is the layer input.
Over the interval of the layer, the layer channels are blended with the base channels. The contribution of the layer is eased-in and eased-out according to the Start, Peak, Release and End parameters. The base is unaffected outside the interval of the layer.
The Effect parameter determines the amount of contribution of the layer.
If Base Hold is 0, the layer input will completely replace the base input when the effect is 1. If Base Hold is 1, the layer will be added to the base.
The interval of the output starts at the minimum of the base and layer. The interval of the output ends at the maximum of the base and layer. The base’s extend conditions are used if the layer lies outside the base.
If the third input is supplied, the Effect page will be overridden by the third input’s first channel, which should contain the effect values over the range of the layer.
Determines how much of the base to blend into the output at points where the layer has an effect.
Matches channels in the base input with ones in the layer input by either index or name. Channel Union causes layer channels that are not in the base to be added to the output.
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 the base input has more channels than the layer input, or when matching by Channel Name if a channel name in the base input cannot be found in the layer input.
Aids in producing smooth rotation blending. The “quaternion” attribute should be in the input CHOP. See the Attribute CHOP.
Shortest Path Rotation Blending
If on, compensate for cyclic channels (such as angles) by always choosing the shortest route between samples when blending.
Defines which channels are rotations for Shortest Path Rotation Blending.
The length of the cycle for Shortest Path Rotation Blending.
Sets how much the layer affects the output. If 0, the output is the base.
Sets the meaning of the next four parameters. Either absolute values, relative to the start/end of the channel, or relative to the current frame. The layer and base are never shifted.
The beginning of the composite interval. Effect is zero at this point.
Where the composite operation reaches maximum effect. This value is held until the release point.
The point at which the effect begins to fall back towards zero.
The end of the composite operation’s effect. The effect reduces to zero again.
The shape of the segment between the Start and Peak indices, or between Release and End.
Some of these parameters may not be available on all CHOP nodes.
To determine the channels that are affected, some CHOPs have a scope string. Patterns can be used in 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 the rate of the first input to resample the others.
Resample At Maximum Rate
Resample to the 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 of the time parameters.
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, the existing parameters are not converted to the new units.
Time slicing is a feature that boosts cooking performance and reduces memory usage. Traditionally, CHOPs calculate the channel over its entire frame range. If the channel needs 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 the 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 to it for display in the graph, but you can override the color with the 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 channel index (0 to NC-1).
The total number of channels.
You can chain the Composite CHOP together to take two or more channels and do an ordered sequence blend. The Composite CHOP takes a control curve and uses it to determine which channel to use with each Composite CHOP working on two channels at a time, creating a sequence blend. The first Composite node processes the first and second channel, the second Composite node processes the result from the first node and the third channel, and so on.
A key component of this network is the Limit CHOP. It processes the control curve so the range is valid for the pair of channels being processed by the associated Composite node.