Houdini 20.0 Nodes Geometry nodes

Unpack USD 2.0 geometry node

Converts “packed USD” primitives into normal Houdini geometry.

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Since 19.0

Overview

USD packed primitives store USD data as attributes on points in a Houdini primitive. This node unpacks all or some of the packed USD prims.

  • You can extract a subset of the packed USD prims, based on various criteria such as prim type and kind.

  • You can output the matched subset as another USD packed primitive, or convert the unpacked USD geometry prims to Houdini polygons.

  • When converting to Houdini geometry, the node converts any USD primvars listed in Import primvars into Houdini geometry attributes.

See how Houdini converts geometry between USD and Houdini for more information.

Parameters

Main

Group

Specify the packed objects to extract. If this is empty, the node extracts all prims. Usually you will click the Select button to the right of the text box to select objects visually in the viewport.

Delete Original Prims

When this is on (the default), the original USD packed prims are not passed though to the output.

Traversal

How to find the USD prims to extract.

Unpack

Output

Whether to output the extracted USD prims as a new USD packed primitive, or as Houdini polygonal geometry.

Pivot Location

Specifies whether to place the packed primitive’s point at the origin of its coordinate frame, or at the center of its bounding box.

Path Attribute

If enabled, creates a SOP primitive attribute containing the scene graph path of the original USD primitive.

Name Attribute

If enabled, creates a SOP primitive attribute containing the name of the original USD primitive.

File Path Attribute

If enabled, creates a SOP primitive attribute containing the file path (or LOP node path) of the original USD primitive’s stage.

Transfer Attributes

When unpacking to regular Houdini geometry, this is a list of patterns matching existing Houdini geometry attributes (not USD attributes) on the USD Packed Primitive that should be transferred onto the output geometry. For example, you might have sent the USD packed primitives through an RBD simulation in Houdini, which wrote position and rotation attributes onto the packed prims, which you want to transfer onto the extracted geometry.

Transfer Groups

When unpacking to regular Houdini geometry, this is a list of patterns matching existing Houdini geometry groups on the USD Packed Primitive that should be transferred onto the output geometry.

Import Data

Import Primvars

When unpacking to regular Houdini geometry, this is a list of patterns matching USD primvars that should be converted to Houdini geometry attributes.

Import Inherited Primvars

Includes primvars that are inherited from parent primitives when unpacking to regular Houdini geometry. The Import Primvars filter is also applied to select which inherited primvars are imported.

Import Computed Visibility

If the visibility attribute is authored on the USD prim, a usdvisibility SOP attribute is created with its value (invisible or inherited). When this option is enabled, the usdvisibility attribute will instead contain the computed visibility for every prim. This can be useful to determine which primitives are visible, but should be used with caution when round-tripping to avoid replacing the original USD visibility attributes.

Import Attributes

When unpacking to regular Houdini geometry, this is a list of patterns matching USD attributes that should be converted to Houdini geometry attributes (in addition to the primvars specified in Import primvars).

These patterns are only matched against custom USD attributes on the prim being imported. USD attributes that are part of a schema have special handling (for example, the faceVertexIndices attribute on a mesh primitive is converted into the topology of the resulting polygons).

Unlike primvars, custom attributes do not specify an interpolation mode. If the attribute’s value is an array, the node guesses the Houdini attribute level (point, vertex, primitive, or detail) based on the number of elements in the array.

Since only primvars can be inherited from parent primitives, the Import Inherited Primvars option does not apply for custom USD attributes.

Non-transforming Primvars

When unpacking to regular Houdini geometry, this is a list of patterns matching USD primvars that should be converted to non-transforming Houdini geometry attributes.

Translate ST primvar to UV

USD generally stores texture coordinates in a primvar named st, while Houdini stores them in an attribute named uv. When this is on, the node automatically converts USD st primvars to uv attributes.

See also

Geometry nodes