Return the USD primitive path that will be used by default on new LOP nodes with a primpath parameter with a default of /$OS.

Set the USD primitive path that will be used by default on new LOP nodes with a primpath parameter with a default of /$OS. This identifies a parameter that is used to create a new USD primitive. Being able to control this default makes it easier to conform to studio-wide standard naming conventions for primitive paths.

Return the USD primitive path that will be used as the default location when creating new collections. If not set, the default value is /collections.

Set the USD primitive path that will be used as the default location when creating new collections. Being able to control this default makes it easier to conform to studio-wide standard naming conventions for primitive paths.

Return the USD primitive type that will be created for holding collections when the destination primitive doesn’t already exist. If not set, the default value is an empty string, indicating that a typeless primitive will be created.

Set the USD primitive type that will be created for holding collections when the destination primitive doesn’t already exist. Being able to control this default makes it easier to conform to studio-wide standard conventions for using primitive types.

Return the USD primitive path that will be used as the default location when creating new lights. If not set, the default value is /lights.

Set the USD primitive path that will be used as the default location when creating new lights. Being able to control this default makes it easier to conform to studio-wide standard naming conventions for primitive paths.

Return the USD primitive path that will be used as the default location when creating new cameras. If not set, the default value is /cameras.

Set the USD primitive path that will be used as the default location when creating new cameras. Being able to control this default makes it easier to conform to studio-wide standard naming conventions for primitive paths.

Return the string that will be used as the default suffix on transform attribute names.

Set the string that will be used as the default suffix on transform attribute names. USD transforms always start with xformOp: followed by the transform type (translate, rotate, transform), followed by an optional suffix that describes the transform. This string is the default Houdini will use in situations where this suffix can be provided, which can help make USD layers authored in LOPs conform to studio-wide standard naming conventions.

Return True if the option to show resolved layer file paths is turned on.

Set the option to control whether panels that show layer file paths should display the exact path set on the layer, or the path after passing it through the USD path resolver. The resolved path will generally be a full path to a file on disk, where the unresolved path may be a relative path, a search path, or a path format that is specific to a custom resolver.

Return True if LOP panes such as the Scene Graph Tree and Scene Graph Details should follow the current node selected in the network editor.

Set the option for LOP panes such as the Scene Graph Tree and Scene Graph Details to follow the current node selected in the network editor. If set to False, these panes will instead show information for the LOP node with its display flag set.

Return True if LOP panes such as the Scene Graph Tree and Scene Graph Details should show information about the USD stage generated by applying any viewport overrides set in the Scene Graph Tree.

Set the option for LOP panes such as the Scene Graph Tree and Scene Graph Details to show information about the USD stage generated by applying any viewport overrides set in the Scene Graph Tree.

Turning this option off will improve the performance of these panes when there are viewport overrides applied to the scene. The tradeoff is that the values shown in the scene graph tree and scene graph details for visibility and activation may not match what is shown in the viewport. However it will better match the scene description that would be used by a final render, as viewport overrides are not included in the USD sent to a final render.

Return True if LOP panes such as the Scene Graph Tree and Scene Graph Details should show information about the USD stage generated by applying any post-layers applied to the parent LOP Network.

Set the option for LOP panes such as the Scene Graph Tree and Scene Graph Details to show information about the USD stage generated by applying any post-layers applied to the parent LOP Network.

Return True if the Sublayer and Reference LOP nodes should automatically use their first USD layer loaded from disk as the resolver context asset path passed to the USD stage to define it’s asset resolver context.

Pass in a value of True if the Sublayer and Reference LOP nodes should automatically use their first USD layer loaded from disk as the resolver context asset path passed to the USD stage to define it’s asset resolver context. The resolver context is used by the USD asset resolver to help find the right files when opening a layer file in the context of a particular stage. Often this resolver context can be determined by looking at the “root” layer of the stage. In the case of LOPs, the first layer loaded by a Sublayer or Reference LOP is the closest thing we have to a “root” layer. This preference makes it easier to implement this workflow. The alternative involves using a Configure Stage LOP as the first node in the LOP Network to explicitly set the resolver context asset path. Similarly this option only affects a Sublayer or Reference LOP if it is the first node in the chain.

Return True if the LOP viewport has been configured to run update tasks in the background.

Pass in a value of True to cause the LOP viewport to run update tasks in the background, which results in better interactivity but allows the viewport display to be temporarily out of sync with the current cooked LOP stage.

Return True if new LOP Networks will be created with the option to load all payloads in the viewport enabled.

Pass in a value of True to cause new LOP Networks to be created with the option to load all payloads in the viewport enabled. Pass in a value of False to disable the loading of payloads in the viewport for any new LOP Networks. No existing LOP Networks are affected by this method. The default value for this preference is True.

Return True if the scene graph tree can allow the user to force the loading of a payload into the viewport which has been prevented from loading by a Configure Stage node. Return False if the scene graph tree should prevent the explicit loading of such payloads. This value ensures that the viewport will only show payloads that have been processed by the LOP network, eliminating a potential mismatch between the scene displayed in the viewport, and the same scene rendered with the USD Render ROP with a different set of loaded payloads processed by the LOP Network.

Set the flag that indicates whether the viewport is allowed to load payloads that have been specified as unloaded by a Configure Stage node.

Return True if USD Primitive Path parameters should provide syntax highlighting and prim path completion hints. Enabling this may cause pauses when editing Primitive Path parameters with very large USD stages.

Set the flag that indicates whether the USD Primitive Path parameters should provide path completion hints.

Return the default meters per unit metric that will be saved into USD layers that do not have this value explicitly set. A value of zero indicates that Houdini’s “Unit Length” option will be used to generate an equivalent meters per unit value.

Set the default meters per unit metric that will be saved into USD layers that do not have this value explicitly set. A value of zero indicates that Houdini’s “Unit Length” option should be used to generate an equivalent meters per unit value.

Return the default up axis value that will be saved into USD layers that do not have this value explicitly set. An empty string indicates that the USD up axis fallback value (pxr.UsdGeom.GetFallbackUpAxis) should be used.

Set the default up axis that will be saved into USD layers that do not have this value explicitly set. An empty string indicates that the USD up axis fallback value (pxr.UsdGeom.GetFallbackUpAxis) should be used. Other acceptable values are Y and Z. Trying to set any other value will raise a hou.ValueError exception.

Saves out the current LOP preferences to $HOME/houdiniX.Y/solaris.pref. This happens automatically when the preferences are modified in the preferences dialog, and when exiting Houdini. But in a batch scripting environment, changes made to these preferences will not be saved automatically, so this method must be used. Returns True is the preference file was saved successfully.

Registers a callback function that is invoked any time one of these preferences is changed.

Deregisters a callback function previously registered with a call to addPreferenceChangeCallback.

Returns the ID of the shader translator for the given node. The ID is specific to Houdini session and can change between them.

Returns the render context name for the given node and output. It is used in the USD material primitive output name, to associate the connected shader with a given renderer.

Creates a new shader primitive and returns a path to the shader primitive output.

Adds an entry to the table of known shader translations. This allows LOPs to find out the USD shader primitives given a shader VOP node, which is necessary for incremental re-translation of shaders.

Returns a shader hou.NodeType given the shader name.

Shader name is generic identifier of the abstract shader entity, and the returned node type is a representation of that shader in a form of the node of that type.

For example, shader "foo" may correspond to a VOP node of type my_namespace::FooShader::2.0.

Given a property on a USD stage, this method returns a hou.ParmTemplateGroup object that describes the parameters that can be placed on an Edit Properties LOP node to control that USD property.

Given a source node parameter, this method returns a hou.ParmTemplateGroup object that describes the parameters that can be placed on an Edit Properties LOP node to control a value of a corresponding USD property.

The returned group contains a control parameter that decides how the USD property is changed and a value parameter, which is very similar to the given parameter, except for disable-when condition and a few other small differences.

Given a property on a USD stage, this method returns a hou.ParmTemplateGroup object that describes the parameters that can be placed on an Edit Properties LOP node to modify the connection of that USD (destination) property to a source attribute.

Set the value of a node parameter tuple from the value of a property on a USD primitive. If the parameter cannot be set because the data type of the parameter is not compatible with the data type of the USD property, or the USD property cannot be found, raises a hou.OperationFailed exception.

This helper method makes it easier to author stage variable expressions for use in USD files. Stage variable expressions are evaluated by USD at stage composition time. They contain a limited set of functions, and allow accessing stage variables which can be set using a Configure Layer node. The full capabilities and syntax of such stage variable expressions is described in the USD documentation, but it is enough to know that the format closely resembles Houdini’s hscript expression language. As such, it can be difficult to specify a stage variable expression in a Houdini parameter without using complex sequences of escape characters.

Take for example the case where you want to reference in a texture map using the following very simple stage variable expression:

`"/project/car/${textureLOD}/decal.exr"`

Note that the backticks around the expression are required to let USD identify this as a stage variable expression. The double quotes indicate that the value of the stage variable expression is a simple string constant, not using any expression functions. Further suppose that your hip file is in /project/car, and you'd like to use the Houdini $HIP variable to express this part of the path. To get this stage variable expression into your USD file, the texture path parameter on a VOP node would need to be:

\`"$HIP/\${textureLOD}/decal.exr"\`

The escape characters make this string somewhat difficult to read, and it may be hard to remember the all the required formatting. The stageVariableExpression python function allows you to set the parameter to evaluate as the following python expression:

hou.lop.stageVariableExpression('"`$HIP`/${textureLOD}/decal.exr"')

The final expression will be identical but note that there are no escape characters, and no need to remember the surrounding back ticks. Instead, the back ticks are used to tell the stageVariableExpression method which parts of the string should be evaluated as hscript expressions.

The sve method also exists as an alias for this funciton, making the resulting python expression much more compact.

This method is simply a shorter alias for the stageVariableExpression method. See help on that method for a full description of its operation.

Returns a list of dicts containing meta data for registered renderer plugins.

Returns a tuple with the display labels of registered renderer plugins.

Returns a tuple with the internal names of registered renderer plugins.

Returns the parameters that can be used to configure the output processor with an internal name that matches the name parameter. See the USD ROP for more information about output processors.

Returns a tuple holding the internal name and user facing label for each output processor plugin in the registry. See the USD ROP for more information about output processors.

This function ensures that a string meets the requirements of a legal USD primitive name that can be used as part of a valid primitive path. Invalid characters such as spaces and most punctuation will be converted to underscores. Note that this means the translation is not reversible. If the original string is already a legal primitive name, the name is returned unchanged.

This function ensures that a string meets the requirements of a legal USD primitive path that can be converted into a psx.Sdf.Path object. Invalid characters such as spaces and most punctuation will be converted to underscores. Note that this means the translation is not reversible. If the original string is already a legal primitive path, the string is returned unchanged.

If the allow_relative value is True, the path is allowed to be a relative primitive path. A relative path is one that starts with ./ or ../. If this argument is False, only absolute paths (which start with /) are allowed. Relative prefixes are simply removed from the path and the returned path will always start with a /.

This method calls the USD Reload method for the specified layer path. In addition, it updates internal Houdini data structures of the reload so that they can update. This method should be used in place of the pxr.Sdf.Layer.Reload or similar methods when running in Houdini.

Setting the recursive parameter to True will cause Houdini to recursively look for other layers referenced by the specified layer, and reload them as well.

Returns a dictionary holding information about the USD library built into Houdini.

The packageurl and packagerevision values may return an empty string if the USD library that ships with Houdini is replaced with a custom USD build.

Returns the minimum USD message severity that will be output to standard output. The USD library can produce a variety of messages indicating error or warning conditions, or just status messages. If such a message is generated while a LOP node is cooking, the message will never be output to the console, regardless of this setting.

Sets the minimum message severity produced by the USD library that should be written to standard output. This method only controls the output of messages produced when a LOP node is not cooking.

Adds a locked copy of a hou.Geometry to a registry, so that it can be used as a USD reference or sublayer.

The returned string is a USD layer identifier that can be used when adding a composition arc.

If an args dictionary is specified, the contents must be pre-converted to be strings. For example: { 't': '1.0' } is valid, but { 't': 1.0 } is not.

Example:

from pxr import Usd
geo = hou.Geometry()
geo.loadFromFile('shaderteapot.bgeo')
stage = Usd.Stage.CreateInMemory()
layer_id = hou.lop.addLockedGeometry('teapot', geo)
stage.GetRootLayer().subLayerPaths.append(layer_id)

See also hou.LopNode.addLockedGeometry

Removes a locked hou.Geometry from the registry, returning a bool to indicate success or failure.

Example:

geo = hou.Geometry()
geo.loadFromFile('shaderteapot.bgeo')
layer_id = hou.lop.addLockedGeometry('teapot', geo)
hou.lop.removeLockedGeometry(layer_id)

Presses the “reload” button on every LOP node with such a parameter. If the reload_viewports parameter is True, this method also clears all USD stages owned by scene viewer panes, which will effectively cause all USD stages in Houdini to be rebuilt from scratch. This is a potentially very expensive operation, but in some cases may be required to force USD to reload and re-resolve paths to assets on disk, such as when the configuration of an asset resolver has been changed.