Where tool prompts, warnings, and errors appear in the user interface.

Where tool help messages (for example, explaining what keys and mouse buttons do in the tool) appear in the user interface.

Whether Houdini shows the key and the name of the command in the viewer when you press a hotkey. This can be useful visual feedback to confirm that the hotkey command ran, or understand what happened if you accidentally press the wrong key.

When this is on, Houdini shows tool notifications, help tips, and hotkey presses for the Message Duration, then hides them. When this is off, each message stays visible until the next message replaces it.

When Message Time Limit is on, the is the number of seconds tool notifications, help tips, and hotkey presses stay visible.

The initial/default setting for the Show Simulation Cache option on the playbar. When turned on, Houdini highlights the cached simulation frames in blue on the timeline.

The initial/default setting for the Show Animation Cache option on the playbar. When turned on, Houdini highlights the cached animation frames in blue on the timeline.

The maximum number of pixels the pointer can move between mouse button press and release to count as a click.

The maximum number of pixels the pointer can move after mouse button press to count as holding the mouse button down.

The minimum number of pixels the mouse pointer must move before Houdini considers it a drag.

The minimum number of pixels the mouse pointer must move when selecting geometry before Houdini considers it selecting and moving the geometry.

Houdini switches to the View tool when you hold or tap Space. When this is on, you can also hold Alt to switch to the View tool.

When this is on, Houdini automatically sets the view pivot based on the selection when you select geometry.

Controls the plane in which you pan.

Controls the line along which you dolly.

Controls how camera zooming works in the viewer.

Sets the color Houdini uses for the network editor background.

When Background is From Theme or Gray, this lets you make the background darker or lighter.

When Background is Custom, this is the background color for the network editor.

When this is on, the info window automatically closes when it loses focus.

This setting is off by default on Linux because different window manager behaviors and focus-follow-mouse settings can make it unreliable.

Set the theme for the node info window. You can set it to use the current application theme, or have its own theme.

Set the theme for the TOPs work item info window. You can set it to use the current application theme, or have its own theme.

Set the theme for the USD prim info window. You can set it to use the current application theme, or have its own theme.

The radius for snapping moved/placed nodes to align with other nodes. Increase this distance to make nodes more likely to move to align with other nodes when dropped.

The radius for snapping wires to connectors. Increase this radius to have wires jump onto connectors from farther away. Decrease it to have wires not jump to connectors until you get closer.

Shaking nodes disconnects them from their wires. This slider controls how far you have to move the mouse back and forth for Houdini to recognize a shake. If you are getting accidental disconnects because Houdini thinks you are shaking, you might want to decrease this. Turn the slider all the way down to disable shaking to disconnect.

The minimum font size for node names, in network units (one unit is roughly one node width). If this is set to 0, there is no minimum size.

The maximum font size for node names, in network units (one unit is roughly one node width). If this is set to 0, there is no maximum size.

When you revert all parameters on a node (using items in the gear menu in the parameter editor), or right-click a parameter and choose Revert to Default, this controls whether it also deletes any existing animation channels on the parameter.

When you revert all parameters on a node (using items in the gear menu in the parameter editor), this controls whether it also reverts parameters set to be invisible.

Controls how much tinting changes the backgrounds of parameters. Lower values make the tinting less intense, higher values make it more intense.

A parameter value has changed from the keyed value but hasn’t been committed yet.

The parameter has a key at the current frame.

The parameter has an animation channel but doesn’t have a key at the current frame.

The parameter expression language is set to Python.

You have disabled this parameter’s animation channel from the Dopesheet user interface.

This parameter’s value is overridden by a CHOP node.

Whether to color code pane tabs.

When Color Pane Tabs is not Off, this controls how Houdini colors the pane tabs.

When Color Pane Tabs is not Off, this controls how intense the tab coloring is.

When this is on, Houdini draws icons in pane tabs to show the pane type. This may help find pane types quickly, but takes more space.

When Show Icons in Pane Tabs is on and this is on, Houdini tints the icons by to the type of pane (for example, viewers, Solaris, animation, and so on). When this is off, Houdini tints the pane tab icons using the current theme.

Normally the desktop manager doesn’t show files if their filename starts with a period (.). When this is on, the desktop manager shows these files.

Shows all files in the desktop manager, even if they don’t seem to be desktop files.

Controls what the desktop manager does with the existing file if you edit a file path interactively in the manager. The default is for Houdini to ask whether you wanted to move or copy the file to the new path. You can change this to always copy or always move.

When this is on, any change you make to a parameter value automatically creates a keyframe. When this is off (the default), you have to manually create keyframes (for example, by pressing K, or alt-clicking the parameter, or right clicking the parameter and choosing Keyframes ▸ Set Keyframe).

See animation basics for more information about setting keyframes.

When this is on, Houdini creates keyframes for all components of the parameter, not just the one that changed. This is important when animating handles. The default is off.

If this is on, when you change a parameter that already has a keyframe at the current frame, Houdini automatically saves the change as the new keyed value. You do not need to explicitly key the values. The default is on.

Automatically turns on the “auto-add to channel list” flag when creating a channel. This is for advanced use cases where Add Parameters with Animation isn’t enough.

When this is set to a number, Houdini creates an extra keyframe at the specified frame (usually frame 1) when you set the initial keyframe in a channel. If this is blank, Houdini doesn’t add extra keyframes. The default is blank (no extra keyframes).

This controls what happens when you press K to add a key in the viewer, or click the big key button in the playbar.

Controls the background color of the animation editor. You can choose Black, Dark Gray, Medium Gray, Light Gray, or use the background color of the current theme, or choose a custom background color. The default is Black.

When New Segment Type is Manual, this is the type to use for new segments.

When New Segment Slope is Manual, this is the slope for new animation curve segments.

When this is on, Houdini automatically modifies channels to hold the value of the last keyframe until the end of the animation. This lets you insert keyframes repeatedly without changing the interpolation of the last segment.

Adds parameters with the autoadd flag.

Adds any parameters that already have keyframes.

When this is on, the channel list expands the selected nodes to include child nodes.

When this is on, the channel list expands the selected nodes to include constraint nodes.

Keeps the channel list selection when nodes are re-selected. When this is off, the channel selection state resets based on the auto-select flag.

When this is on and you add parameters to the channel list, Houdini opens a new animation editor window there isn’t one already visible.

When this is on, the channel list follows channel references and CHOP exports. When this is off, you will see the result of the expression in the graph editor, but will not be able to edit any keyframes.

When this is on, parameters that are in the channel list show a small dot in the bottom right corner of the parameter in the parameter editor.

When this is on, the color of the channel dot in the parameter editor uses the channel’s curve color in the animation editor.

If this is on and you load a file with animation on a parameter that doesn’t exist, Houdini creates spare parameters for the animation. If this is off, Houdini discards animation for non-existant parameters.

This can be useful when loading an old scene file is from an older version, or uses an old version of an asset. However, you can turn this off if you do not want to clutter your nodes with obsolete parameters.

Controls what node panes other than the viewer show.

You can create overrides in the scene graph tree pane, such as toggling visibility. These overrides, indicated by a red dot in the pane, only affect an internal “viewport stage” used by the viewer, overlayed on the “real” stage.

When this is off (the default), non-viewer panes (such as the scene graph details pane) show the state of the “real” USD stage, not the “viewport” stage. When this is on, non-viewer panes show the overlayed viewport stage, rather than the underlying “real” stage constructed by the network.

For example, when this is off, if you hide a prim from the viewer using the scene graph tree, the details pane will still show it as visible.

In addition to viewport overrides created in the scene graph tree, the hou.LopNetwork.editablePostLayers method creates “post-layers” on a LOP Network that affect both the viewport and final renders. When this is off, the scene graph tree and scene graph details panes ignore the post-layers. This can be useful for debugging post-layers, otherwise you should leave this off.

Controls whether file paths shown in the scene graph layers pane are before or after the resolver.

The prim path parameter value on new LOP nodes. This controls the path at which Houdini creates a new prim in the USD scene tree. The default expression /$OS puts the prim at the root level and names the prim after the node ($OS means the name of the current node).

It’s a good idea for people working in LOPs to edit the primitive path whenever they put down a LOP that creates a prim, because the default is not a very good general policy.

You may want to use a different expression for your studio, or for different departments (for example, /World/$OS or /Layout/$OS), but it should include $OS to help avoid namespace collisions.

The collections prim path parameter on new LOP nodes. This controls the path on which Houdini adds collection attributes. The default is /collections. You may want to use a different path for your stuido (for example, /World/collections).

When Houdini tries to create a collection attribute on the primitive, if the prim doesn’t already exist, Houdini will create a prim of this type.

LOP nodes that create lights will generally put them under this prim (creating the prim if it doesn’t exist), though some will allow you to choose a different prim. The default is /lights.

You may want to choose a different default place to create lights for your studio, or for different departments (for example, /World/lights or /Layout/lights).

LOP nodes that create or reference cameras will generally put them under this prim (creating the prim if it doesn’t exist), though some will allow you to choose a different prim. The default is /cameras.

You may want to choose a different default place to create cameras for your studio, or for different departments (for example, /World/cameras or /Layout/cameras).

The default value for the Transform Description parameter on Transform LOP nodes. Houdini appends this to the transform attribute name. The default is $OS (the node name), to avoid naming collisions with attributes created by different nodes. Collisions can cause unexpected results, where the Transform node overwrites an existing transform rather than creating a new one.

You may want to change this based on your studio’s own transform attribute naming conventions.

When Secure Selection is on, you must switch to the Select tool (hold or tap S) to change the selection. When Secure Selection is off, you can select objects/components in any tool without having to switch to the Select tool.

This controls the default. You can change the setting using the secure selection icon button on the left side of the viewer.

By default, box/lasso selection ignores hidden geometry.

When this is on, loop selections in the viewport create full loops even if this means passing through regions of irregular topology. When this is off (the default), loops stop if they reach a point with multiple “exits”.

For example, if you select a vertical (longitudinal) edge on a polygon mesh sphere, turning this on lets you select a loop that passes through the poles of the sphere. If this option is turned off, the loop will stop at the poles.

Turn on the construction plane automatically when entering the Curve tool at the OBJ level.

Turn on the construction plane automatically when entering the Curve tool at the SOP level.

Turn on the construction plane automatically when entering the Bones tool.

Turn on the construction plane automatically when entering the Path tool.

Higher values make Houdini try harder to keep the cache size down, saving memory at the expense of speed.

id: sopcache.level.val

The size in megabytes of the SOP cache. The default is 1024 (1 GB).

The amount of memory to use to cache object transforms.

Whether Houdini uses the Memory Limit.

Click this button to clear the Object cache immediately.

When this is on, if you keyframe a handle, Houdini opens a floating animation editor if an animation editor is not already visible.

The initial orientation for transform handles in the 3D viewer.

When turned on, rotation handles in the 3D viewer start in gimbal mode. In gimbal mode, the rotation rings are always aligned so manipulating them only affects the angle of the corresponding axis.

Whether the Light and Camera Object handles start in Local or World space.

When this is on, Houdini draws the move axes pointing toward and away from the viewer. When this is off, Houdini only draws the axes pointing toward the viewer. The default is off.

Houdini draws planes between the move axes. Dragging these widgets moves the handle along two axes at once.

When this is on, dragging between the handle’s move axes moves the handle along two axes at once.

When Show Negative Axes is on, Allow Dragging Between Move Axes is on, and this is on, if a drag is both over a back-facing move axis and between two forward facing axes, Houdini will interpret it as a planar drag.

When this is on, Houdini draws a line during planar drags to show the distance the handle has moved across the plane.

You can drag on the invisible “trackball” defined by the rotation rings to free-rotate the handle.

When this is on, Houdini hides a rotation ring if it’s parallel to the view direction.

When this is on, Houdini shows an extra ring perpendicular to the view. Dragging this ring rotates the handle around the view direction.

When this is on, dragging in the viewer with a handle visible will manipulate the handle, without you having to drag directly on the handle.

Not all handles support this option. When multiple handles are visible, Houdini manipulates the handle closest to the mouse pointer that supports this option.

Controls how indirect dragging affects a move (translate) handle.

The “spider” handle combines a move and rotate handle. It is sometimes used on character joints.

For handles with both translate and rotate parts, this controls whether indirect dragging moves or rotates.

For handles with both translate and vector rotation parts, this controls whether indirect dragging moves or rotates.

For handles with both translate and scale parts, this controls whether indirect dragging moves or scales.

Draws short perpendicular lines along the curve representing frames.

Controls the the size of the ticks. Increase this for longer ticks, or decrease for shorter ticks.

Controls the density of the ticks. When this is 1, Houdini shows ticks for every frame. If you set it to 2, Houdini shows every other frame, it you set it to 3 Houdini shows every third frame, and so on.

When this is on, the length of the ticks depends on their proximity to the skeleton during its animation.

When Variable Tick Length is on, this is the distance (in Houdini units) from the skeleton at which the keyframe tick size are smallest.

When this is on, the Frames Before and Frames After preferences control how many frames of animation the motion path shows before and after the current frame. When this is off, the motion path shows all frames in the current frame range.

When Limit Number of Frames is on, the number of frames before the curren time the motion path shows.

When Limit Number of Frames is on, the number of frames after the current time the motion path shows.

Sample times between frames to create a smoother curve.

When Smooth Values Between Frames is on, the number of samples to take between each frame. Higher values give a smoother curve, but may hurt performance.

Controls what the motion path shows when the before/after range goes past the current frame range.

When this is on, handles appear in all split viewports. When this is off, each handle only appears in the viewport under the mouse pointer.

Draws a small label describing the handle part near the mouse pointer, for example “Rotate X”.

Show Houdini’s value ladder when you press on a handle part.

When a handle is visible you can drag in empty space to manipulate the handle without having to be exactly on it. This controls which handle part indirect drags affect.

Adjusts the size of the handles in the viewer.

Adjusts the line width Houdini uses to draw the handles.

Adjusts the brightness of the handles in the viewer. You may want to change this depending on which view background color you use.

Turn this on to set separate default 3D alignments for move handles, rotate handles, and scale handles. When this is off, you can set one alignment for all handle types.

When Separate Defaults for Move, Rotate, and Scale is on, this sets the default 3D alignment for move handles. When Separate Defaults for Move, Rotate, and Scale is off, this sets the default alignment for all handle types.

When Separate Defaults for Move, Rotate, and Scale is on, this sets the default 3D alignment for rotate handles.

When Separate Defaults for Move, Rotate, and Scale is on, this sets the default 3D alignment for scale handles.

Houdini draws flat square grab handles between the move axis arms. Dragging these widgets lets you move freely across the plane defined by the two adjacent axes.

How Houdini draws the grab widget at the center of the move handle. Dragging this widget lets you move freely across the view plane.

Controls where Houdini draws move arrows in combination move/rotate handles. (See full transform mode.)

Controls where Houdini draws the planar drag widgets in combination move/rotate handles. (See full transform mode.)

The length of the axis move arms in translate mode, and in full transform mode when Draw Move Arrows is Inside

The space between the handle center and the start of the the axis move arms in translate mode, and in full transform mode when Draw Move Arrows is Inside

The length of the axis move arms when Draw Move Arrows is Outside

The space between the rotation sphere and the start of the axis move arms when Draw Move Arrows is Outside.

Adjusts the size of the arrow tips on the translate axes.

Adjusts the size of the center widget.

Adjusts the size of the planar drag widgets.

How Houdini interprets drags on the rotation rings.

How much of the rotation ring face away from the view direction to draw. When the slider is all the way to the left, Houdini only draws the half ring facing toward the viewer. When the slider is all the way to the right, Houdini draws the full rings.

Whether to draw grab handles at the points where the axis rings. Dragging these widgets lets you rotate the handle freely.

When Grab Dots at Ring Crossings is on, this controls the size of the dots.

Whether to draw a “trackball” sphere inside the rotation rings in combination move and rotate handles. You can drag the sphere to rotate the handle freely. The trackball sphere is only visible when the mouse pointer is over the handle. (See full transform mode.)

When Draw Rotation Sphere in Move + Rotate Handle is on, this controls how Houdini draws the trackball sphere.

When Rotation Sphere Look, this controls the size of the trackball sphere. This is relative to the size of the rotation rings. A value of 1.0 draws the trackball the same size as the rotation rings. Smaller values draw the trackball inside the rings. Larger values draw the trackball outside the rings.

Controls the size of the extra rotation ring in the view plane. This is relative to the size of the rotation rings. A value of 1.0 draws the trackball the same size as the rotation rings. Smaller values draw the view rotation ring inside the rings. Larger values draw it outside the rings.

Whether controls are visible behind objects.

When See Controls Through Skin is on, this controls how transparent controls behind objects appear. Lower values are more transparent.

Whether to show or hide controls while the animation is playing.

Whether to show or hide controls while you drag the current frame along the timeline.

Whether to show or hide controls while you drag a handle.

Whether to show a toolbar above the widgets. Buttons on the toolbar let you lock the widget position, set and remove keys, lock or unlock the value, and revert the value to the default.

Whether to show the name of the parameter above the widget.

You can “dock” widgets together so they move as one unit. This controls whether docked widgets show the name of the parameter above the widget.

Whether to show a slider next to numeric parameters. When this is off, numeric parameters only show a text box for editing the number.

When you drag a numeric parameter with two or more components into the viewer, you can choose to create a “trackpad” widget. This controls whether to show the trackpad widget. When this is off, trackpad widgets only show text boxes for editing the numbers.

Whether to show the parameter label next to the widget.

When Label is on, this controls the color of parameter labels in floating parameter widgets.

Whether Houdini draws a shadow below floating parameter widgets.

Whether Houdini draws a filled rectangle behind floating parameter widgets. You can change the color and transparency of the background using the Background Color option below.

The color for non-label text in floating parameter widgets.

When Background is on, the color of the background rectangle behind floating parameter widgets.

Apply syntax coloring to expressions in parameters.

Highlight matching bracets and quotes in parameters.

Show help for expression functions as you type in parameters.

When this is off, right-clicking a parameter and choosing Expression ▸ Edit Expression/String opens a Houdini text editor window you can use to edit the parameter contents. If you turn this on, Houdini runs the external program specified in the $EDITOR environment variable instead of showing the Houdini text editor.

Houdini writes the parameter contents out to a temporary file, then launches the external program in $EDITOR with the temporary file path as an argument. Houdini freezes until the external program exits. Then Houdini copies the (possibly edited) contents of the temporary file back into the parameter.

If you are using a GUI editor application, you need to pass arguments in $EDITOR to set the text editor to launch a new process instead of switching to an existing copy of the application, and not detach from the starting process. For example, to use VS Code as the external editor, $EDITOR should be:

code --new-window --wait

Apply syntax coloring to expressions in the text editors.

Highlight matching bracets and quotes in the text editors.

Show a toolbar with common text commands above text editors. This preference does not apply to multi-line parameters.

Show line numbers in the left margin of text editors.

Increases or decreases text size in text editors. The default is 100.

Apply syntax coloring in the HScript textport.

Highlight matching bracets and quotes in the HScript textport.

Show help for HScript commands as you type in the HScript textport.

Auto-complete in the HScript textport does not require an exact match.

Whether Houdini should run OpenCL programs on a CPU or GPU. Any change to this option only takes effect the next time you start Houdini.

Choose which computing device Houdini should run OpenCL programs on. Any change to this option only takes effect the next time you start Houdini.

The length, in memters, of one Houdini scene unit. You can use the preset menu to choose from common conversions, such as inches. Some unit-specific simulation nodes (DOPs) use this preference.

The length, in memters, of one Houdini scene unit. You can use the preset menu to choose from common conversions, such as ounces. Some unit-specific simulation nodes (DOPs) use this preference.

Whether Houdini should show a warning dialog when you load scene files containing nodes that SideFX has marked as “deprecated” (subject to removal in future versions of Houdini). The default is off.

What Houdini does when you choose File ▸ Save. These options do not affect File ▸ Save As.

Houdini saves the current viewpoint and settings of viewers to the scene file on disk so the view is the same when you load the file again. This controls which viewers saves the state for.

You can choose to save files as Plain Text instead of Binary. Although plain text files will be much larger, this could be useful in special circumstances, for example if you need to store your scene files in a textual version control system.

You can always save a plain text version of the current file using File ▸ Save As Plain Text.

Whether Houdini automatically saves the current file every few minutes. You can change the frequency with the Save Every option below. The default is off (no auto save).

When Auto Save is on, this controls how often, in minutes, Houdini automatically saves the file.

Path to the diff executable to use for comparing files. Houdini uses this program when you choose File ▸ Show Changes.

For example, to use VS Code as the diff tool, set this to the path to the code command line program.

The arguments to pass to the diff program command line. Houdini replaces $OLDPATH and $NEWPATH in this string with the file paths to compare.

For example, to use VS Code as the diff tool, set the arguments string to:

--diff $OLDPATH $NEWPATH

For some file comparisons, Houdini writes the files out to temporary files and calls the diff program on the temporary files. If your diff program allows naming the “before” and “after” sides, you can use $OLDTITLE and $NEWTITLE, which will contain nicer names for the two sides than the temporary file paths.

Path to the executable to use for comparing folders.

The arguments to pass to the folder diff program command line. Houdini replaces $OLDPATH and $NEWPATH in this string with the directory paths to compare.