Houdini 22.0 Nodes Geometry nodes

LOP Import 2.0 geometry node

Since 19.0

This node imports the USD primitives specified by the LOP Path and Primitives parameters. The imported primitives are represented as USD packed primitives.

The primitives to be imported are specified by selecting the paths of one or more USD primitives using a primitive pattern. Optionally, the USD hierarchy can be further traversed to import the descendants of these primitives that match a specific criteria.

Parameters

LOP Path

LOP node to import from.

Primitives

The USD primitives to import. This parameter accepts any USD primitive pattern. Primitives that do not match the Purpose filter are excluded.

Exclude Inactive Primitives

When turned on, any inactive USD primitives matched by the Primitives pattern will not be imported. Ignoring deactivated primitives is typically the expected behavior, but importing them can be useful for reactivating the primitives in SOPs via the usdactive attribute.

Import Point Instances

When turned off (the default), a PointInstancer primitive matched by the Primitives pattern is imported as a single USD packed primitive representing the whole point instancer.

When turned on, point instancers matched by the Primitives pattern are instead imported as one USD packed primitive per point instance. Each packed primitive references the instance’s prototype primitive, is positioned with the instance’s transform, and records the point instancer’s path and the instance’s index in its usdsrcprimpath and usdindex intrinsics. The point instancer’s per-instance primvars are imported as point attributes, along with id, v, w, and accel (from the ids, velocities, angularVelocities, and accelerations attributes), and a usdvisibility attribute for instances listed in invisibleIds. This is the same result as importing the point instancer primitive and unpacking it with the Unpack USD SOP.

The Primitives pattern can select a subset of the instances using the instance id syntax described in primitive patterns, for example /geo/trees[0-99] or /geo/trees[{@id % 2 == 0}]. A point instancer path without an instance id selection imports all of its instances.

Note

The Traversal parameter does not apply to point instances, only one level of instancing is expanded (an instance whose prototype is itself a point instancer is imported as a packed primitive for that nested instancer), and the Path Attribute and Name Attribute hold the path and name of the instance’s prototype primitive.

Because the transforms of point instances can change every frame, all point instances are re-imported when the Import Frame changes.

Purpose

Sections of a USD hierarchy can be marked to be used for a specific purpose. Only sections marked as the default purpose or one of the specified purposes are traversed when unpacking the USD packed primitives.

Traversal

Optionally, the USD hierarchy can be further traversed to import descendants of the selected Primitives that match a criteria.

Note

Equivalent behavior could also be achieved through a primitive pattern (for example, using the descendants auto collection).

No Traversal

Creates a USD packed primitive for each USD prim matched by the Primitives pattern.

Components

Creates a USD packed primitive for each prim with kind component.

Gprims

Creates a USD packed primitive for each gprim.

Groups

Creates a USD packed primitive for each prim of type group.

Strip Layers Above Layer Breaks

When turned on, removes all layers created above Layer Break nodes on every input to the source LOP node. This restricts the imported primitives to those created after Layer Breaks.

Time Sample

Specifies whether to import static or animated geometry from the LOP node.

Import Frame

When Time Sample is set to Animated, this is the frame at which to cook the LOP node and sample the stage. When importing animated geometry, this could be set to $FF.

Static Import Frame

When Time Sample is set to Static, this is the frame at which to cook the LOP node and sample the stage. This should be set to a constant value such as $RFSTART.

Path Attribute

When turned on, creates a SOP primitive attribute containing the scene graph path of the original USD primitive.

Name Attribute

When turned on, creates a SOP primitive attribute containing the name of the original USD primitive.

Display As

Specifies how to display the USD packed primitives in the viewport.

Full Geometry

The full geometry is displayed in the viewport.

Point Cloud

Only the points of the geometry are displayed. This takes less memory and is faster to render.

Bounding Box

Only display the bounding box of the geometry in the viewport.

Centroid

Display a single point at the center of the bounding box.

Hidden

Don’t display the geometry in the viewport.

Pivot Location

Specifies the packed primitive’s point position.

Centroid

Use the center of the world position of the USD prim’s bounding box.

Origin

Use the world position of the origin of the USD prim.

See also

Geometry nodes