| Since | 18.0 |
このノードは、LOPsが
SOP Import LOPを使用してこのジオメトリをUSD Primとして取り込む方法、または、ディスクからジオメトリファイルを読み込むタイミングに影響を与えるDetailアトリビュートを設定します。
パラメータ
Import Group
これを有効にして、インポートするグループ名(または、グループ構文をスペースで区切ったリスト)を指定します。 これを有効にして、フィールドを空っぽのままにすると、すべてのジオメトリが取り込まれます。
Import Group Type
これを有効にして、 Import Group がポイントまたはプリミティブのどちらのグループなのかを指定します。
Import Path Prefix
取り込んだPrimにパスPrimがなかったことで(mesh_0のような)自動生成された名前が付けられている場合、または、パスPrimがあってもそのパスが(/から始まっていない)相対パスであった場合、
このノードは、その名前/パスの頭に自動的にこのパスを追加します。
これは、“パスなし” Primsを単一ブランチ下に整理しておくための方法です。
(ジオメトリ階層を作成する方法を参照。)
(デフォルトは/$OSです。これは、このノードの名前を使ってルートPrim下に“パスなし” Primsを配置します。)
Layer Save Path
これを有効にすると、ジオメトリを含んだレイヤーのSave Pathメタデータにこのファイルパスを設定します。
USD Renderノードを使ってUSDを書き出す時、(出力処理の後に)このファイルパスを使ってジオメトリが.usdレイヤーファイルに保存されます。
Sample Frame
このジオメトリを取り込んで生成されたUSDレイヤー上にStart FrameメタデータとEnd Frameメタデータを設定します。
この値は、特に
USD Stitch Clips ROPを使ってBGEOファイルシーケンスをValue Clipに結合する時に役立ちます。
Primitive Definition
Parameters in this group guide the translation process in terms of how USD primitives are generated from the source SOP geometry.
Packed USD Primitives
What to do with packed USD primitives in the imported SOP geometry.
Overlay Transforms
Import the transformation of the packed USD primitive as an override (Over) prim. This makes it easy to transform the packed USD prims without unpacking them.
Ignore
Ignore packed USD primitives in the source SOP geometry.
Other Primitives
What to do with regular non-packed primitives (points, curves, polygons, spheres, and so on).
Define
Create the USD prims for the imported geometry if they don’t already exist. This is the standard way to import geometry.
Overlay
Create the USD prims as overrides. They will only be visible as changes to any prims that exist at a lower level with the same paths. This may be useful where you only want to import and modify certain attributes from SOPs onto existing USD geometry.
Overlay Transforms
Like “Overlay”, but only imports transform data.
Define Only Leaf Primitives
Author intermediate primitives (for example, any Xform prims created for the Import path prefix) as overrides instead of definitions. This means if they don’t match up with underlying prims in lower layers, the leaf prims won’t be added to the scene. This is useful if you only want to import the geometry if its ancestors already exist in the scene tree.
(Note that all of the data is still imported, it just may not be visible in the scene graph tree or the viewport.)
Packed Primitives
What to do with SOP-native packed primitives.
Create Xforms
Creates an Xform prim from the packed primitive’s transform and attributes, and the packed primitive’s geometry is imported underneath.
Create Native Instances
Import the geometry in packed primitives as instanceable references. This imports each piece as a prototype under a Prototypes prim under the Import Path Prefix prim.
Create Point Instancer
Import the geometry in packed primitives as point instanced geometry. This imports each unique piece as a prototype under the point instancer prim.
You can assign a SOP primitive attribute to the packed primitive named usdinstancerpath to specify the USD scene graph path of the instancer.
Unpack
Only imports the packed primitive’s geometry.
Unlike the Create Xforms mode, this does not create any additional hierarchy, and is equivalent to 
unpacking the packed primitive prior to being imported.
This can be useful for importing multiple pieces of geometry without merging their attributes.
Agents
What to do with agent primitives. In all modes, a prim is created from the agent primitive’s transform and attributes, and the agent’s geometry and animation are imported underneath.
Create Instanced SkelRoots
Imports the agent’s skeleton and geometry as instanceable references to a SkelRoot prim enclosing the skeleton and skinned primitives.
This imports each unique agent definition as a prototype under an agentdefinitions prim under the Import Path Prefix prim.
Create SkelRoots
Creates a SkelRoot prim enclosing the agent’s skeleton and skinned geometry, which is imported underneath.
This will be less efficient than Create Instanced SkelRoots for a large crowd, but can be useful for e.g. importing a single character where instancing is unnecessary.
Create Instanced Skeletons
Imports the agent’s skeleton as an instanceable reference to a Skeleton prim.
This imports each unique agent definition as a prototype under an agentdefinitions prim under the Import Path Prefix prim.
Create Skeletons
Imports the agent’s skeleton as a Skeleton prim under the agent’s Xform prim.
This will be less efficient than Create Instanced Skeletons for a large crowd, but can be useful for e.g. importing a single character where instancing is unnecessary.
Create SkelAnimations
Only imports the agent’s joint animation, creating a SkelAnimation prim.
This can be used to efficiently import a sequence of frames, since the agent’s skeleton and rest geometry are typically unchanged between frames.
NURBS Curves
What to do with NURBS curve primitives.
Convert to Basis Curves
Import the curves as a BasisCurves primitive.
This only supports cubic curves, but is useful for rendering through Hydra.
Create NURBS Curves
Import the curves as a NurbsCurves primitive.
This provides complete round-tripping of NURBS curves, but has limited support for rendering through Hydra.
Kind Authoring
How to assign kinds to imported prims.
All Geometry is One Component
Set root primitives in the imported tree to Component. Do not set kinds on descendants.
Nested Groups and Components
Set leaf primitives in the imported tree to Component. Set branch primitives to Group.
Nested Assembly, Groups, and Components
Set root prims in the imported tree to Assembly. Set intermediate branch prims to Group. Set leaf prims to Component.
None
Do not set kinds on the imported prims.
Path Attributes
A (comma or space-separated) list of names of SOP primitive string attributes to use to use as prim paths to put the SOP geometry into. The default is path,name. See geometry hierarchy above.
If the list has more than one attribute, the importer checks each attribute for the first non-empty value.
If the string value a full path, that path is used as the USD scene graph path for that primitive. If the string is a relative path (or just a name), the string is appended to the Import Path Prefix string to generate a full scene graph path.
If none of the listed attributes exist on a given SOP primitive, or all values are an empty string, the importer generates a name automatically (for example, sphere_0).
Import HeightFields as Mesh
If the source SOP geometry contains a height field volume, it will be imported as polygonal mesh. Other layers will be imported as vertex primvar if the values are varying, or constant primvar if the values are constant.
Import Data
These parameters affect the conversion of SOP geometry attributes into USD attributes and primvars, and the choice between default and time sampled value authoring.
Author Time Samples
Whether values imported from SOPs should be authored as default values for the corresponding USD attributes, or as a time sample (at the time in the timeline).
(When the USD system is asked for an attribute value, it returns the default if no time samples exist on the attribute. Otherwise it returns a value interpolated from the time sample data.)
If SOP is Time Dependent
If the SOP node the geometry comes from is time-dependent (is animated or contains animated values), write time samples. Otherwise, write defaults.
If Not Specifically Excluded
Author all values as time samples except for attributes listed in the Single Value Attributes parameter.
Never
Author all values as defaults.
(This is the only parameter on this node you can’t pre-configure on the geometry with the 
USD Configure SOP. This is because it requires a “live” SOP, not just attribute values embedded in the geometry.)
Topology Attributes
Controls whether USD topology attributes should be authored as time sampled or default values.
Animated
If you know that topology is changing in the source geometry over time, choose this option to record topology attributes as time samples in the USD scene graph. Having animated topology can be very expensive during playback, so only use this option when necessary.
Static
Write topology attributes as default values. This can make playback much faster, but limits how the topology can change over time.
None
Do not author topology attributes.
This is useful when USD data is sent to SOPs for processing, then brought back into LOPs. Using this option tells the importer that the geometry topology has not changed in this process, so only the changing point positions or other primvars will be imported.
Attributes
A space-separated list of attribute names/patterns specifying which SOP attributes to import into USD as primvars.
In addition to matching attribute names directly, there are some values with special meanings:
bounds
Authors the USD extent attribute using the calculated bounding box of the associated SOP geometry.
visibility
Authors the USD visibility attribute based on the value of the usdvisibility geometry attribute.
See importing attributes for information on how the importer deals converts certain well-known Houdini attributes to their USD equivalents.
Indexed Attributes
A space-separated list of attribute names/patterns specifying which SOP attributes to import into USD as indexed primvars.
If a SOP attribute matches this pattern, the importer authors the primvar as an indexed array of values (that is, an array of values call primvars:name, and an array of indices into those values called primvars:name:indices).
Preparing an indexed primvar can be expensive for attributes that are not integers or strings. You should only use indexed primvars where it is likely to result in significant savings in storage size due to a small number of unique values being used across a large number of components.
Import as Single Element Array
A space-separated list of attribute names/patterns specifying which SOP attributes to import into USD as primvars with Constant interpolation (an array with a single value for the whole primitive), regardless of whether the SOP geometry attribute is a point, primitive, or vertex attribute. If multiple values could be chosen for a particular USD primitive, the importer chooses the first value it encounters.
Importing as a single element array (versus Import as Single Value) can be useful since it allows the primvar’s interpolation to be overridden without changing the primvar’s type.
Import as Single Value
A space-separated list of attribute names/patterns specifying which SOP attributes to import into USD as primvars with Constant interpolation and a single value for the whole primitive, regardless of whether the SOP geometry attribute is a point, primitive, or vertex attribute. If multiple values could be chosen for a particular USD primitive, the importer chooses the first value it encounters.
This is the default behavior for how detail attributes are imported.
This is similar to Import as Single Element Array, but the primvar’s type is a scalar value instead of an array with a single element (for example, vector3f instead of vector3f[]).
Boolean Attributes
A space-separated list of attribute names/patterns specifying which integer SOP attributes should be converted to primvars of type bool.
Set Default Values
A space-separated list of attribute names/patterns specifying which SOP attributes to always author as default values for USD primvars (never time samples). This is the list of exclusions when Author Time Samples is set to “If Not Specifically Excluded”.
Partition Attributes
A space-separated list of attribute names/patterns specifying which SOP primitive string attributes represent subsets of the geometry. For mesh and curve primitives, the importer puts elements with the same value for this attribute into their own geometry subsets.
The importer will try to set the subset name to the attribute value, but may need to change the name make it a legal USD primitive name. The importer stores the raw attribute value on the geometry subset prim as Custom Data with the key partitionValue.
Subset Groups
A space-separated list of group names/patterns specifying SOP primitive groups. SOP polygon and curve primitives in each group will be imported as a geometry subset, named for the group.
USD Custom Attributes
A space-separated list of attribute names/patterns specifying which SOP attributes to import into USD as attributes (rather than primvars).
Translate UV Attribute to ST
Convert the SOP vertex attribute uv into a USD primvar called primvars:st. Whether you need to turn this on depends on which renderer you are using and how your shaders are authored. If you are rendering with Karma, leave this off.
(As of this writing there is no strict standard for texture coordinate naming in USD, but the use of st is a common convention, whereas in SOP geometry, using uv is the common convention.)
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