Blend channel node

Combines two or more chops in input 2, 3 and so on, by using a set of blending channels in input 1.

The Blend CHOP combines two or more chops in input 2, 3 and so on, by using a set of blending channels in input 1. The blending channels cause different strengths of the chops to contribute to the output of the chop. It works like the Blend SOP.

Input 1 acts as the control input, which contains the blend weight channels for the rest of the inputs. There is one channel in it for each of the blended chops coming in on input 2, 3 and so on.

The first channel in input 1 is input 2's blend weight, the second channel in input 1 is the input 3's blend weight, and so on. There should be as many blend channels in input 1 as there are inputs, excluding input 1.

The interval of the output of the chop is the interval of input 1 (the blend channels).

If input 2 onwards are just poses, it’s acceptable, as the chop blends between poses by using extend conditions.

Each blend input affects the result without reducing the effect of the others. You can exaggerate beyond each of the inputs by setting their Blend > 1, and you can also use negative values. When all blend channels are 0, you get smooth transitions as any of the blend channels ease out of zero.

Blend ¶

Method

The blend method.

Proportional

Each blend source contributes to the result according to its blend weight. If the blend weights do not add up to one, they are scaled so that they do.

Difference

The input 2 is always the “base”, which is the default behavior of the Blend CHOP. There are blend channels for all the other inputs, and when they are all zero, you get base. If any one blend channel is 1 and the others are zero, then your output is the same as the input that corresponds to that blend channel.

Omit First Weight Channel

The weight channel for the base input has no effect when using the Differencing method. So, the channel is omitted if this option is on.

Rotation Blending

Rotation channels typically don’t blend well when treated as Euler angles, and straight linear blending can result in flips and odd rotations. Instead, shortest path blending can be used to properly blend orientations represented by Euler rotation angles.

Euler

Rotation channels are blended like any other channel.

Shortest Path (Linear)

Two inputs are blended using shortest path rotation blending. If more than two blend inputs are connected, use Fast Linear.

Shortest Path (Fast Linear)

Multiple inputs are blended together using shortest path rotation blending.

Use Rotation Hint

When rotation blending is set to Shortest Path, a rotation hint can be specified when recreating the Euler angles. This hint will modify the starting values of the Euler angles so that they are close to the rotation hint. When off, the hint is ignored and the Euler angles will not be altered from their computed values.

This can be useful if many CHOPs in the same network are working with rotations, then all these CHOPs can have their rotation hints set to the same values to keep the Euler angles similar.

Common ¶

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

Scope

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:

`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`.

`t?`

The `?` matches a single character. `t?` matches two-character channels starting with t.

`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 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.

Units

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).

Time Slice

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.

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`.

Graph Color

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.

Examples ¶

Blend Example for Blend channel node

This example demonstrates how the Blend CHOP combines several channels together using an interpolated blend weight control.

Channel nodes

• Design audio filters and sound materials for the spatial audio system.

• Imports an animation clip from an agent primitive.

• Calculates the area under a channel’s graph, which is the same as calculating the integral of a channel, or integrating the channel.

• Receives audio input from the analog audio ports or the digital port.

• A 14-band equalizer which filters audio input channels in the same way that a conventional band equalizer uses a bank of sliders to filter fixed-frequency bands of sound.

• Manually tap the beat of a piece of music, and automatically generate a repeating ramp or pulse that continues to keep time with the music after the taps stop.

• Combines two or more chops in input 2, 3 and so on, by using a set of blending channels in input 1.

• Performs multi-dimensional, example-based interpolation of channels.

• Creates channels from the value of its parameters.

• Contains a VOP network that can manipulate channel data.

• Runs a VEX snippet to modify channel data.

• Layers (blends) the channels of one CHOP on the channels of another CHOP.

• Create up to forty new channels.

• Combines two or more CHOP inputs using a list of weights specified as parameters.

• Returns an Object Local Transform.

• Returns an Object Parent Transform.

• Returns an Object World Transform.

• Constrains rotation so it always points toward a target position.

• Compares two objects and returns information on their relative positions and orientations.

• Compares two objects and returns information on their relative positions and orientations.

• Returns an Object Pretransform.

• Applies an transformation offset after evaluating a constraint.

• Reparent an object.

• Position an object on a path and orient it to the path’s direction.

• Position and Orient an object using point positions from a geometry.

• Combines multiple chops by blending the inputs in sequence.

• Combines two chops by using a single weight specified as a parameter.

• Position and Orient an object using the surface of a geometry.

• Takes translate, rotate, and/or scale channels and transforms them.

• Produces multiple copies of the second input along the timeline of the first input.

• Counts the number of times a channel crosses a trigger or release threshold.

• Creates cycles.

• Delays the input, and can be run in normal or time-sliced mode.

• Removes channels coming from its input.

• Turns data from device inputs into transform data

• Time-warps the node’s first input (source clip) using its second input (reference clip) as a reference.

• Extracts any information from a DOP simulation that is accessible through the dopfield expression function.

• Outputs the maximum amplitude in the vicinity of each sample of the input.

• Fixes discontinuity of rotation data after cracking matrices

• A convenient tool for exporting channels.

• Export Constraints Network on any object

• Export Transforms to Constraints Network of many objects

• Modify input channels by using expressions.

• Only sets the extend conditions of a chop, which determines what values you get when sampling the CHOP before or after its interval.

• (Deprecated) Extracts the current world or local space bone transforms from a geometry object.

• Extracts locomotion from an animation clip.

• (Deprecated) Creates channels from the specified derived transforms, node parameters and CHOP channels for pose-space deformation.

• Reads in channel data from an FBX file.

• Used for controlling other CHOPs.

• Get the state of a chop as it was one frame or time slice ago.

• Imports channels from other CHOPs.

• Imports channels from other OPs.

• Reads in channel and audio files for use by chops.

• Smooths or sharpens the input channels.

• Computes when position channels are stationary.

• Divides the input channels into groups, cooking the contained network for each group.

• Provides more complicated math functions than found in the Math CHOP such as trigonometic functions, logarithmic functions, and exponential functions.

• Turns input values for the gamepad or joystick device into channel outputs.

• Uses a geometry object to choose a sop from which the channels will be created.

• The engine which drives Inverse Kinematic solutions using the Handle object.

• Sample and hold the value of the first input.

• Solves inverse kinematics rotations for bone chains.

• Returns an identity transform.

• Converts rows and/or columns of pixels in an image to CHOP channels.

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

• Generates channels for bone objects based on a bone chain and an end affector.

• Returns an invert transform of the input.

• Creates a jiggling effect in the translate channels passed in.

• Turns key presses into channel output.

• Adds lag and overshoot to channels.

• Mix weighted layers of keyframed animation from multiple Channel CHOPs to a base Channel CHOP.

• Provides a variety of functions to limit and quantize the input channels.

• Converts channels of all its input chops into binary channels and combines them using a variety of logic operations.

• Uses a channel in the first input to index into a lookup table in the second input, and output values from the lookup table.

• The MIDI In CHOP reads Note events, Controller events, Program Change events, and Timing events from both midi devices and files.

• The MIDI Out CHOP sends MIDI events to any available MIDI devices.

• Perform a variety of arithmetic operations on and between channels.

• Takes multiple inputs and merges them into the output.

• Outputs X and Y screen values for the mouse device.

• Turns input values for the Connexion space mouse into channel outputs.

• Post multiplies all the input transformations.

• Similar to the Pipe In/Out CHOPs in Network mode.

• Makes an irregular wave that never repeats, with values approximately in the range -1 to +1.

• Used as a place-holder and does not have a function of its own.

• Compares two objects and returns information on their relative positions and orientations.

• Creates channels representing the transforms for a chain of objects.

• Generates sounds in two ways.

• Marks the output of a sub-network.

• Filters an audio clip, and then applies other audio effects.

• Produces translate and rotate channels to move Objects according to the positions of particles in a POP Network.

• Filters audio input using one of four different filter types.

• Translates english text into a series of phonetic values.

• Pipes data from custom devices into a CHOP, without needing the Houdini Developers' Kit or knowledge of Houdini internals.

• Transmit data out of Houdini to other processes.

• Attempts to extract the fundamental pitch of a musical tone from the input audio.

• Store a transform pose for later use by evaluating the input.

• Computes the difference between two poses.

• Takes translate, rotate, and/or scale channels and transforms them using the pretransform of the given object.

• Generates pulses at regular intervals of one channel.

• Renames channels.

• Reorders the first input CHOP’s channels by numeric or alphabetic patterns.

• Resamples an input’s channels to a new rate and/or start/end interval.

• Takes all its inputs and appends one chop after another.

• This time-shifts a CHOP, changing the start and end of the CHOP’s interval.

• Reorganizes a list of channels.

• Calculates the slope (or derivative) of the input channels.

• The rendering engine for producing 3D audio.

• Calculates the frequency spectrum of the input channels, or a portion of the channels.

• Edit the channel data by using direct manipulation of cubic or Bezier handles in the graph of the CHOP.

• Creates vibrations influenced by the input channels, as if a mass was attached to a spring.

• Caches the input motion in the node on command, and then uses it as the node’s output.

• (Deprecated) Stashes the bone transforms and pose-drivers for use by the Pose-Space Deform SOP and Pose-Space Edit SOP nodes.

• Preserves the shape of channels and the sampling rate, but resamples the channels into a new interval.

• Allows for the simplification of complex networks by collapsing several CHOPs into one.

• Control the flow of channels through a CHOPnet.

• This converts an input node in Current Frame mode to a Time Range mode by re-cooking it multiple times.

• This time-shifts a CHOP, re-cooking the node using different time.

• Takes translate, rotate, and/or scale channels and transforms them.

• Contains a VOP network that can manipulate transform data.

• Combines a chain of translate, rotate, and/or scale channels.

• Adds an audio-style attack/decay/sustain/release (ADSR) envelope to all trigger points in the input channels.

• Shortens or lengthens the input’s channels.

• This function is a sub-set of the waveform CHOP.

• Performs vector operations on a set or sets of channels.

• The Voice Split CHOP takes an audio track and separates words out into different channels.

• The Voice Sync CHOP detects phonemes in an audio channel given some audio phoneme samples and pro…

• Time-warps the channels of the first input (the Pre-Warp Channels) using one warping channel in the second input.

• Creates a waveform that is repeated.