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.

All Parameters Example files

See also: Composite, Interpolate, Sequence

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. In it there is one channel 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.

Advantages of Difference Method

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.

Parameters

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

In this default behavior of the Blend CHOP, the input 2 is always the “base”. 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

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

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

Blend

$HFS/houdini/help/examples/nodes/chop/blend/Blend.cmd

Load | Launch

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

Usages in other examples

Example name Example for