Houdini 20.5 Reference Panes

Channel list and channel groups

The channel list is used to select the parameters that are displayed in the animation editor and on the timeline.

On this page

Overview

Channels record how the value of a parameter changes over time. You can think of a channel as a parameter animation.

A channel is an extra object associated with a parameter. It stores keyframe information, essentially acting as a keyframe container for the parameter. If you delete all the keyframes on a parameter, you end up with a parameter with an empty channel (a channel that does not hold any keyframes).

The channel list holds the parameters on which keyframes are set. Parameters can be added to the channel list automatically or manually. When you select a node, the channel list shows the node parameters that are already keyed or have been added to the channel list.

Parameters that are added to the channel list can be displayed in the animation editor. When you set keyframes, Houdini sets keyframes for the parameters in the channel list.

The channel list can also hold a special type of channel called channel primitives. Channel primitives are not associated with any parameter. They are animation curves that are stored along with geometry and are optimized for use in the animate state. When a character’s control is selected in the animate state, channel primitives for that control are added to the channel list, and you can interact with them like regular channels. See the available options for channel primitives in the channel list.

View the channels in the channel list

To see the parameters that are in the channel list, click the Channel List button on the right side of the playbar, or open the animation editor.

The Channel List button on the playbar displays channel list statistics including the number of parameters that have keys at the current frame, the number of selected parameters, the total number of parameters in the channel list, and whether channel list filtering is active.

Click the Channel List button to open a floating Channel List window.

Channel List window

The Filter toolbar at the bottom of the Channel List pane allows you to display only the parameters that match a given pattern. You can choose from common patterns in the pop-up menu at the right end of the Filter field. You can also click the translate, rotate and scale toggle buttons to quickly filter the transform parameters.

In the animation editor, the channel list is displayed in the bottom left Channel List sub-pane. You can click the name of a parameter to show or hide the channel in the graph display.

Graph editor view of the animation editor

The parameter editor also gives a visual hint of whether a parameter is selected in the channel list by displaying a colored underline for the selected parameters. See parameter underline for more information.

Selected channel list parameters are underlined in the parameter editor

Select, add and modify channels in the channel list

See the parameter context menu for descriptions of the options available when clicking the channels in the channel list.

To...Do this

Select multiple parameters in the channel list

drag to select multiple parameter names.

or

Hold ⇧ Shift and click to select groups of adjacent parameters.

or

Hold CTRL and click to select or deselect individual parameters.

In the below channel list, only the Scale parameters are selected. The rest of the parameters are in the channel list, but are not selected. The graph editor only displays the selected parameters.

Add a parameter to the channel list

In the parameter editor, click the parameter name (for all components in the parameter, such as all translates) or an individual component (such as Translate Y), and choose Channels ▸ Add to Channel List.

or

In the parameter editor, ⇧ Shift + a parameter name or individual component.

or

Drag a parameter name or individual component from the parameter editor into the Channel List pane.

Only display a particular parameter in the channel list

Replaces any parameters in the channel list with this parameter.

In the parameter editor, click the parameter name (for all components in the parameter, such as all translates) or an individual component (such as Translate Y), and choose Channels ▸ Isolate in Channel List.

or

In the parameter editor, ⇧ Shift + a parameter name or individual component.

Keep a parameter always visible in the channel list

In the Channel List pane:

  • Click the pin icon next to the parameter to pin it. Click the icon again to unpin it.

  • Click the pin icon beside the node name (above the list of individual parameters) to pin all the parameters in the channel list for that node.

Mute/unmute the selected channels

Muted channels don’t affect the animation.

  1. In the channel list, select the channels to mute/unmute.

  2. click in the channel list ▸ Channels ▸ Unmute Channels or Mute Channels.

or

Mute/unmute individual channels from the parameter editor by clicking the parameter name, and choosing Channels ▸ Mute Channel or Unmute Channel.

Select the nodes from the selected channels

  1. Select the parameters from the channel list.

  2. Hover over the channel list and press S. The object will be selected in the viewport.

or

  1. Click the gear icon at the top right of the Channel List pane.

  2. Choose Select Nodes From Selected Channels.

Note

This is useful on character rigs, as it will allow you to select nodes for viewport interaction without having to pick the object in the viewport. This comes in handy when selecting finger controllers.

Set multiple parameter values at once

  1. In the channel list, drag to select multiple parameter value fields (the number boxes on the right column of the channel list). You should see a text selection in the value field.

  2. Enter a new number. Press Enter to confirm or ESC to cancel.

Change multiple parameter values at once

  1. In the channel list, drag to select multiple parameter value fields (the number boxes on the right column of the channel list).

  2. click to bring up the value ladder and drag to adjust all the selected parameter values at the same time.

Copy/Paste multiple parameter values at once

  1. In the channel list, select a set of adjacent parameters to copy.

  2. With the mouse over the channel list, press CTRL + C to copy the values.

  3. Select the same number of adjacent parameters to paste the values into (for example, if 3 parameters were previously copied, select 3 parameters in this step).

  4. With the mouse over the channel list, press CTRL + V to paste the values.

Tip

All of the options when clicking on a parameter in the parameter editor are also available for the parameters in the channel list. You can use the + modifier shortcuts on parameter names and individual components. If you don’t remember the shortcuts, you can find them by clicking on a parameter.

Tip

When you start to manually add parameters to the channel list, you may notice that the Animation Editor window pops up in front of the screen. You can turn this off by setting the Open Animation Editor if Closed animation preference.

Auto-add to the channel list

When you select an object, certain parameters are automatically added to the channel list. Each object type has a list of parameters that are automatically added to the channel list by default, and these are usually the most important parameters for animation, such as translation (position), rotation, and scale. Some objects have other parameters that are automatically added by default, for example, the Light Intensity parameter for the Ambient Light node.

You can customize the parameters to auto-add for each object. This is useful when you only want to key a couple of parameters, for example, Translate Y and Translate Z of a bouncing ball. Then whenever you select and key the ball, only those parameters will be keyed.

To...Do this

Set a parameter to be automatically added to the channel list

  1. Select the object.

  2. In the parameter editor, click a parameter name or individual component, and choose Channels ▸ Auto-Add.

  3. Select away from the object, then select the object again to view the parameters that are automatically added to the channel list.

Tip

When you create a digital asset, you can choose the asset’s parameters to auto-add in the Parameters pane of the asset’s type properties window.

Auto-select in the channel list

When you select an object, certain parameters are automatically added to the channel list, and by default, all of these auto-added parameters are also selected in the channel list. You can change the default selection state of a parameter by turning off the Auto-Select flag. This is used to control the selection of parameters that you may not want to keyframe all the time.

To...Do this

Set a parameter to be automatically selected when it is added to the channel list

  1. Select the object.

  2. In the parameter editor, click a parameter name or individual component, and choose Channels ▸ Auto-Select.

  3. Select away from the object, then select the object again to view the parameters that are automatically selected in the channel list.

Tip

When you create a digital asset, you can choose the asset’s parameters to auto-select in the Parameters pane of the asset’s type properties window.

Keep channel list selections

When you select an object, you can choose to reset the channel list selection to its default state or keep the current channel list selection.

Tip

If you keep the channel list selection, you can quickly switch between different objects in the animation editor without having to always reselect the channels.

To...Do this

Keep the current channel list selection

In the animation preferences (Edit ▸ Preferences ▸ Animation), turn on Keep Channel List Selection.

or

On the playbar, click the Channel List Refresh button and turn on Keep Channel List Selections.

Channel primitives

click the channel primitive in the channel list to bring up the following options:

Set Keyframe

Sets a keyframe on the channel primitive at the current frame.

Remove Keyframe

Removes any keyframe on the channel primitive at the current frame.

Step to Previous Key

Go to the previous keyframe on this channel primitive.

Step to Next Key

Go to the next keyframe on this channel primitive.

Unmute Channel

Turns on the channel so that it affects the animation.

Mute Channel

Turns off the channel so that it does not affect the animation.

Extrapolation

Set the channel extrapolation of the selected channels. Choose from the following extrapolation modes: Default, Hold, Cycle, Extend, Slope, Cycle Offset, and Oscillate. The extrapolation can be applied before and/or after the channels end. See Edit Channel Properties for descriptions of the different extrapolation modes.

Channel Properties

Opens an Edit Channel Properties window that allows you to edit channel metadata such as how to extend the channel before and after the keyframed animation.

Channel groups

Channel groups are groups of parameters. They allow you to easily see, select, and keyframe different groups of parameters. You can also build hierarchies of channel groups, so that selecting a parent group selects all the parameters in its subgroups. For example, in character animation, you can set up a channel group for a character with sub-groups for arms, legs, head, etc. Then while you are animating the character, you can quickly and easily select the appropriate groups of parameters to keyframe.

You can create and manage channel groups in the Channel List pane and in the animation editor:

  • In the Channel List pane, press G to split the pane into a Channel Groups sub-pane on top and a Channel List sub-pane on the bottom.

  • In the animation editor, the channel groups are displayed in the top left Channel Groups sub-pane.

To...Do this

Select and display the parameters in the channel group

Click the name of the group in the Channel Groups sub-pane. The channels in the group will be selected and displayed in the channel list.

Selecting a parent group shows all the subgroup channels in the channel list.

Create a new channel group

  1. Select the parameters in the channel list.

  2. Drag and drop into the Channel Groups sub-pane.

or

  1. Select the parameters in the channel list.

  2. on any of the selected parameters and choose Channels ▸ Create Channel Group.

or

in the Channel Groups sub-pane and choose Create Empty Group.

Create a subgroup

  1. In the Channel Groups sub-pane, select the existing group you want to be the parent of the new group. If no group is selected, a group will be created at the top level.

  2. In the channel list, select the parameters you want in the group.

  3. Click the gear icon at the top right of the Channel Groups sub-pane.

  4. Choose Create Group from Selected Channels.

Create channel groups for an object

Creates nested channel groups for the object parameters that are keyed or have been automatically added to the channel list. If you have organized the parameters of the object into tabs, Houdini will create nested channel groups corresponding to the organization of the parameters.

In the network editor, click on the object node and choose Parameters and Channels ▸ Create Nested Channel Groups.

Add parameters to an existing group

  1. Select the parameters in the channel list.

  2. Drag and drop the selected parameters on the group name in the Channel Groups sub-pane.

  3. From the Drop Actions menu that pops up, choose Add channels to ‹group›.

or

  1. Select the parameters in the channel list.

  2. on the group in the Channel Groups sub-pane.

  3. Choose Add Selected Channels List To Group.

or

In the Channel Groups sub-pane, drag and drop any group into another group and choose one of the options from the Drop Actions menu that pops up.

Remove parameters from a group

  1. In the channel list, select the parameters you want to remove.

  2. Drag and drop the selected parameters on the name of the group you want to remove them from.

  3. From the Drop Actions menu that pops up, choose Remove channels from ‹group›.

Rename a channel group

  1. Select the name of the group. Click the name again.

  2. Type the new name and press Enter.

Keep the parameters in the channel group always visible in the channel list

Click the pin icon next to the group in the Channel Groups sub-pane. The channels in the group will also be pinned in the Channel List pane. Click the icon again to unpin it.

Click the pin icon at the top level group to pin all the channels for all the groups.

Create a take containing the parameters in a group

Press on the group and choose Create Take from Group(s).

Modify channel groups

Use the HScript commands chgadd and chgop:

chgadd newgroup
chgop newgroup set `strreplace(chgroup("oldgroup"), 
                               "old_name", "new_name")`

Note

Channel groups are global for the entire scene file. Copying a node will not modify channel groups.

Tip

To create a single CHOP network node that includes all the parameters from a channel group, click on the channel group and choose Motion FX ▸ Create Clip. Alternatively, if you have multiple parameters in the channel list, click on the playbar and choose Motion FX ▸ Create Clip.

Keyframes in the channel list and channel group

To...Do this

Set keyframes on the parameters in the channel list

Press K to add keyframes to all parameters or selected parameters in the channel list. The Global Set Key animation preference determines which parameters the keyframes are added to. You can also set the Global Set Key preference on the playbar.

Remove keyframes on the parameters in the channel list

Hover the mouse over the channel list and press ⌦ Del to remove the keyframes from the selected parameters in the channel list at the current time.

Delete channels on the parameters in the channel list

Hover the mouse over the channel list and press Ctrl-Del to delete the selected channels from the channel list.

Set keyframes on the parameters in a channel group

click a channel group and choose Set Keys on Selected Group(s).

Remove keyframes on the parameters in a channel group

click a channel group and choose Remove Keys on Selected Group(s).

Color coding in the channel list

Houdini color codes the background of parameter text boxes in the parameter editor and channel list according to the current channel and keyframe status.

Parameter background

State

Black

No channel

This parameter is not animated. It has no channels associated with it.

Green

Keyed

This parameter is animated (controlled by an expression) and you are on a keyframe.

Yellow

Pending changes

This keyed parameter has been changed, but hasn’t been explicitly keyed. You need to explicitly key a changed parameter if auto-commit is turned off.

You can set Houdini to automatically commit changes on keyframes.

Blue

'Tween

This parameter is animated (either with keyframes or an expression), but you are not on a keyframe.

(Click the name of a parameter to switch between showing the current value and the expression.)

Orange

Overridden by CHOPs

This parameter is currently controlled by a channel operator (CHOP).

Light blue

Muted channel

This parameter is animated (either with keyframes or an expression), but the channel is muted in the dopesheet.

Light yellow

Empty channel

This parameter has an empty channel (a channel that doesn’t hold any keyframes). If you delete all the keyframes on the graph, you end up with a parameter with an empty channel.

You can delete the channel on the parameter ( click the parameter and choose Delete Channels) to change the parameter to a black background, or add a single key to turn the parameter into a single keyframe channel (green background).

Purple

Non-default expression language

This parameter uses a different expression language from the current default. Note that this does not indicate which expression language the parameter is set to, only that it is not the current default. Since the default is usually HScript, this often indicates that the parameter has a Python expression.

See python parameter expressions for more information.

The playbar’s keyframe markers and keyframe button also use some of the same color codes to give a quick status of all the keys at the current frame.

See also

Panes

General

Animation

Rendering

Advanced

Other