Miêu Tả Cảnh Phổ Quát (Universal Scene Description)

Nhập Khẩu Tập Tin POV-Ray (Importing USD Files)

USD files typically represent the scene as a hierarchy of primitives, or prims. Individual prims contain data to describe scene entities, such as geometry, lights, cameras and transform hierarchies. Blender's USD importer converts USD prims to a hierarchy of Blender objects. Like the USD exporter, the importer does not yet handle more advanced USD concepts, such as layers and references.

Những kiểu dữ liệu hỗ trợ bao gồm:

• Máy Quay Phim (Cameras)

• Đường Cong (Curves)

• Nguồn Ánh Sáng (Lights)

• Nguyên Vật Liệu (Materials)

• Khung Lưới (Meshes)

• Primitive Shapes

• Âm Lượng/Thể Tích (Volume)

For more information on how the various data types are handled, see the following descriptions of the Import Options.

Ghi chú

When importing a USDZ archive, it is important to carefully consider the Import Textures option to determine whether and how to copy texture files from the zip archive.

Hình Học Cơ Bản Nền Tảng Macro (Xform and Scope Primitives)

USD provides an Xform prim type, containing transform data, which can be used to represent transform hierarchies and to organize the scene. Such Xform prims are imported as Blender empty objects.

USD also supports Scope primitives, which are entities that do not contain transform data, but which serve to group other element of the scene. Blender doesn't have an exact counterpart to the concept of a scope, so such primitives are imported as Blender empties located at the origin. This is an imperfect representation, because empty objects have a transform and Scopes do not, but this approach nonetheless helps preserve the structure of the scene hierarchy.

PointInstancer Primitives

USD provides a UsdGeomPointInstancer prim type, containing instances that are scattered on a primitive's points.

These are imported into Blender as Point Clouds using a Bộ Điều Chỉnh các Nút Hình Học (Geometry Nodes Modifier) and the Nút Thực Thể Hóa trên Điểm (Instance on Points Node).

Hoạt Họa (Animations)

The importer supports two types of animation:

• Animating transforms: If a USD primitive has time-varying transform data, a Transform Cache constraint will be added to the imported Blender object.

• Animating geometry: Animating mesh and curve geometry is supported by adding a Mesh Sequence Cache modifier to the imported data. Geometry attribute (USD Primvar) animation is currently supported only for Color Attributes and UVs. Note that USD file sequences (i.e. a unique file per frame) are not yet supported.

Nguyên Vật Liệu (Materials)

If a USD mesh or geometry subset has a bound material, the importer will assign to the Blender object a material with the same name as the USD material. If a Blender material with the same name already exists in the scene, the existing material may be used, depending on the Material Name Collision option. Otherwise, a new material will be created.

If the USD material has a USD Preview Surface shader source, the Hiển Thị Cổng Nhìn (Viewport Display) color, metallic, and roughness are set to the corresponding USD Preview Surface input values.

There is also an Import USD Preview option to convert USD Preview Surface shaders to Blender Principled BSDF shader nodes. This option can be lossy, as it does not yet handle converting all shader settings and types, but it can generate approximate visualizations of the materials.

Định Hướng của Hệ Thống Tọa Độ (Coordinate System Orientation)

If the imported USD is Y up, a rotation will be automatically applied to root objects to convert to Blender's Z up orientation.

Tùy Chọn Nhập Khẩu (Import Options)

The following options are available when importing from USD:

Chung Chung (General)

Chắn Lọc Đường Dẫn (Path Mask)

Chỉ Nhập Khẩu tập hợp con (subset) của cảnh USD, tức cái bắt nguồn từ đối tượng cơ bản nhất định nào đó.

Bao Gồm (Include)

Duy Đối Tượng Cơ Bản Nhìn Thấy Được (Visible Primitives Only)

Do not import invisible USD primitives. Only applies to primitives with a non-animated visibility attribute. Primitives with animated visibility will always be imported.

Defined Primitives Only

When disabled this allows importing USD primitives which are not defined, such as those with an override specifier.

Đặt Phạm Vi Khung Hình (Set Frame Range)

Cập nhật khung hình khởi đầu và kết thúc của cảnh để khớp với những khung hình của kho lưu trữ USD.

Kiến Tạo Bộ Sưu Tập (Create Collection)

Thêm toàn bộ các đối tượng đã nhập khẩu vào bộ sưu tập mới.

Đường Dẫn Tương Đối (Relative Path)

Select the file relative to the blend-file.

Tỷ Lệ (Scale)

Giá trị để đổi tỷ lệ các đối tượng nhập khẩu tương quan với tọa độ gốc thế giới.

Tỷ Lệ Cường Độ Ánh Sáng (Light Intensity Scale)

Tỷ lệ cho cường độ ánh sáng của các nguồn sáng nhập khẩu.

Các Tính Chất Tùy Chỉnh (Custom Properties)

Behavior when importing USD attributes as Custom Properties.

Không (None):

Does not import USD custom attributes.

User:

Imports USD attributes in the userProperties namespace as custom properties. The namespace will be stripped from the property names.

All Custom:

Imports all USD custom attributes as custom properties. Namespaces will be retained in the property names.

Thể Loại Đối Tượng (Object Types)

Máy Quay Phim (Cameras)

Chuyển đổi giữa chế độ góc nhìn phối cảnh xa gần và chế độ góc nhìn trực giao.

Đường Cong (Curves)

Import curve primitives, including USD basis and NURBS curves. (Note that support for Bézier basis is not yet fully implemented.)

Nguồn Ánh Sáng (Lights)

Import lights. Does not currently include USD dome, cylinder or geometry lights.

Nguyên Vật Liệu (Materials)

Import materials.

Khung Lưới (Meshes)

Nhập Khẩu Bảng Pha Màu.

Thể Tích (Volumes)

Import USD OpenVDB field assets.

Point Clouds

Imports USD UsdGeomPoints as a Point Cloud (Mây Điểm Chấm) object.

USD Shapes

Imports USD primitive shapes (cubes, spheres, cones, ect) as Blender meshes.

Display Purpose

Render (Kết Xuất)

Include primitives with purpose render.

Proxy (Đại Diện)

Include primitives with purpose proxy.

Hướng Dẫn (Guide)

Include primitives with purpose guide.

Material Purpose

Attempt to import materials with the given purpose. If no material with this purpose is bound to the primitive, fall back on loading any other bound material.

All Purpose:

Attempt to import allPurpose materials.

Xem Trước (Preview):

Attempt to import preview materials. Load allPurpose materials as a fallback.

Toàn Phần (Full):

Attempt to import full materials. Load allPurpose or preview materials, in that order, as a "fallback."

Hình Học (Geometry)

Tọa Độ UV

Đọc tọa độ UV của khung lưới.

Thuộc Tính Màu (Color Attributes)

Convert the USD mesh displayColor values to Blender's Color Attributes.

Mesh Attributes

Read USD Primvars as mesh attributes.

Phân Hóa (Subdivision)

Create Subdivision Surface modifiers based on the USD SubdivisionScheme attribute.

Kiểm Nhận các Khung Lưới (Validate Meshes)

Check the imported mesh for corrupt data and fix it if necessary. When disabled, erroneous data may cause crashes displaying or editing the meshes. This option will make the importing slower but is recommended, as data errors are not always obvious.

Dàn Dựng (Rigging)

Hình Mẫu (Shape Keys)

Imports USD blend shapes as Blender's Hình Mẫu (Shape Keys).

Khung Rối (Armatures)

Imports USD skeletons as Blender's Khung Rối (Armatures).

Nguyên Vật Liệu (Materials)

Nhập Khẩu Toàn Bộ các Nguyên Vật Liệu (Import All Materials)

Also import materials that are not used by any geometry. Note, when this option is false, materials referenced by geometry will still be imported.

Nhập Khẩu Xem Trước USD (Import USD Preview)

Convert USD Preview Surface shaders to Principled BSDF shader networks.

Create World Material

Converts the first discovered USD dome light to a world background shader.

Bật Tính Năng Pha Trộn Nguyên Vật Liệu (Set Material Blend)

If the Import USD Preview option is enabled, the material blend method will automatically be set based on the opacity and opacityThreshold shader inputs, allowing for visualization of transparent objects.

Tên Nguyên Vật Liệu Xung Đột (Material Name Collision)

Phương pháp hành xử khi tên của nguyên vật liệu nhập khẩu xung đột với nguyên vật liệu hiện có.

Biến Thành Độc Nhất (Make Unique):

Nhập Khẩu từng nguyên vật liệu USD làm nguyên vật liệu Blender độc nhất.

Tham Chiếu cái hiện Tồn Tại (Reference Existing):

Nếu một nguyên vật liệu có cùng tên đã tồn tại rồi thì hãy tham chiếu đến nguyên vật liệu đó thay vì nhập khẩu.

Chất Liệu (Textures)

When importing a USDZ package, the following options specify whether and how texture asset dependencies of the USD should be copied from the zip archive so they can be loaded into Blender.

Nhập Khẩu Chất Liệu (Import Textures)

Behavior when importing textures from a USDZ archive.

Không (None):

Don't import textures. Note that, with this option, material textures may fail to be resolved in Blender.

Đóng Gói (Packed):

Import textures as packed data in the Blender file.

Sao Chép (Copy):

Copy files to the directory specified in the Textures Directory option.

Thư Mục Chất Liệu (Textures Directory)

Path to the directory where imported textures will be copied, when the Import Textures mode is Copy.

Note that the default textures directory is the relative path //textures, which requires the Blender file to have been saved before importing, so the relative path can be resolved.

Tên Tập Tin Xung Đột (File Name Collision)

Behavior when the name of an imported texture file conflicts with an existing file.

Sử Dụng cái Hiện có (Use Existing):

If a file with the same name already exists, use that instead of copying.

Viết Đè Lên (Overwrite):

Overwrite existing files.

Particles and Instancing

Scene Instancing

Import USD scene graph instances as collection instances, otherwise they are imported as copies.

Xuất Khẩu Ra Tập Tin USD (Exporting to USD Files)

Universal Scene Description (USD) files can contain complex layering, overriding, and references to other files. Blender's USD Exporter takes a much simpler approach. When exporting, all visible, supported objects in the scene are exported, optionally limited by their selection state. Blender does not (yet) support exporting invisible objects, USD layers, variants, etc.

Những kiểu dữ liệu hỗ trợ bao gồm:

• Meshes (of different kinds, see below).

• Cameras (perspective cameras only at the moment, not orthogonal ones).

• Light (all types except area lights).

• Hair (exported as curves, and limited to parent strands).

• Volume (both static and animated volumes).

• Khung Rối (Armatures)

When exporting an animation, the final, evaluated mesh is written to USD. This means that the following meshes can be exported:

• Static meshes.

• Deforming meshes; here the topology of the mesh does not change, but the locations of the vertices change over time. Examples are animated characters or bouncing (but not cracking) objects.

• Arbitrarily animated meshes; here the topology does change. An example is the result of a fluid simulation, where splashes of fluid can break off the main body.

• Metaballs are exported as animated meshes.

Ghi chú

To export the Blender scene as a USDZ archive, set the file extension of the output file to .usdz. The exported USDZ package will be a zip archive containing the USD and its texture file dependencies.

Shot from Spring exported to USD and opened in USDView.

Các Tùy Chọn về Xuất Khẩu (Export Options)

The following options are available when exporting to USD:

Chung Chung (General)

Cơ Bản Gốc (Root Prim)

If set, add a transform primitive with the given path to the stage as the parent of all exported data.

Bao Gồm (Include)

Duy Lựa Chọn (Selection Only)

Khi được chọn thì chỉ các đối tượng được chọn mới được xuất khẩu. Các đối tượng đã được thực thể hóa, ví dụ như các bộ sưu tập đã được thực thể hóa trong cảnh, được coi là 'được chọn' khi thực thể của chúng đã được chọn.

Duy Hữu Hình (Visible Only)

Only exports objects that are not hidden. Invisible parents of exported objects are exported as empty transforms.

Animation (Hoạt Họa)

When checked, the entire scene frame range is exported. When unchecked, only the current scene frame is exported.

Blender Data

Các Tính Chất Tùy Chỉnh (Custom Properties)

Exports Custom Properties as USD attributes. The Namespace property is used to determine the namespace that the attributes are written to.

Namespace

If set, add the given namespace as a prefix to exported custom property names. This only applies to property names that do not already have a prefix (e.g., it would apply to name bar but not foo:bar) and does not apply to Blender object and data names which are always exported in the userProperties:blender namespace.

By default, userProperties namespace is used.

Blender Names

Author USD custom attributes containing the original Blender object and object data names.

Allow Unicode

Preserves UTF-8 encoded characters when writing USD prim and property names (requires software utilizing USD 24.03 or greater when opening the resulting files).

Tham Chiếu Tập Tin (File References)

Đường Dẫn Tương Đối (Relative Paths)

Use relative paths to reference external files (i.e. textures, volumes) in the exported USD file, otherwise use absolute paths.

Convert Orientation

Convert orientation axis to a different convention to match other applications. Blender uses Y Forward, Z Up (since the front view looks along the +Y direction). For example, its common for applications to use Y as the up axis, in that case -Z Forward, Y Up is needed.

Trục Hướng Trước/Hướng Lên Trên (Forward / Up Axis)

By mapping these to different axes you can convert rotations between applications default up and forward axes.

Xform Ops

The type of transform operators to use to transform prims.

Translate, Rotate, Scale:

Export with translate, rotate, and scale Xform operators.

Translate, Orient, Scale:

Export with translate, orient quaternion, and scale Xform operators.

Matrix:

Export matrix operator.

Sử Dụng các Sắp Đặt cho (Use Settings for)

Determines the whether to use Viewport or Render visibility of collection, modifiers, or any other property that can be set for both the Viewport and Render.

Thể Loại Đối Tượng (Object Types)

Khung Lưới (Meshes)

Exports Mesh Objects

Nguồn Ánh Sáng (Lights)

Exports Light Objects USD does not directly support spot lights, so those are not exported.

Máy Quay Phim (Cameras)

Exports Camera Objects Only perspective cameras are exported.

Đường Cong (Curves)

Exports Curve Objects

Point Clouds

Exports Point Cloud Objects as UsdGeomPoints primitives.

Thể Tích (Volumes)

Exports Volume Objects

Tóc/Lông (Hair)

Exports parent hair strands are exported as a curve system. Hair strand colors are not exported.

Hình Học (Geometry)

Ánh Xạ UV (UV Maps)

When checked, includes UV coordinates for exported meshes. The name of the UV map in USD is the same as the name in Blender.

Rename UV Maps

Exports UV maps using the USD default name (st) as opposed to Blender's default name (UVMap).

Pháp Tuyến (Normals)

When checked, includes normals for exported meshes. This includes custom loop normals.

Tam Giác Hóa (Triangulate)

Triangulates the mesh before writing. For more detail on the specific option see the Triangulate modifier.

Dàn Dựng (Rigging)

Hình Mẫu (Shape Keys)

Export shape keys as USD blend shapes.

Absolute shape keys are not supported.

Khung Rối (Armatures)

Export Armatures and meshes with Armature Modifiers as USD skeletons and skinned meshes.

Những Giới Hạn:

• Modifiers in addition to Armature modifiers will not be applied.

• Bendy bones are not supported.

Duy Xương Biến Dạng (Only Deform Bones)

Only export deform bones and their parents.

Nguyên Vật Liệu (Materials)

Exports material information of the object. By default the exporter approximates the BSDF Nguyên Tắc (Principled BSDF) node tree by converting it to USD's Preview Surface format.

When a mesh has multiple materials assigned, a geometry subset is created for each material. The first material (if any) is always applied to the mesh itself as well (regardless of the existence of geometry subsets), because the Hydra viewport does not support materials on subsets. See USD issue #542 for more information.

Ghi chú

If USD Preview Surface Network and MaterialX Network are disabled, the material is set to the viewport materials of meshes.

USD Preview Surface Network

Approximates a BSDF Nguyên Tắc (Principled BSDF) node tree to by converting it to USD's Preview Surface format.

Cảnh báo

Not all nodes are supported; currently only Diffuse, Principle, Image Textures, and UVMap nodes are support.

MaterialX Network

Generates material shading graphs using the MaterialX standard. This standard is designed to support a high amount of interoperability among DCCs <Digital Content Creation>. In Blender, MaterialX supports most of the shader nodes and their functionality but has a few caveats (see below).

Implementation Caveats

When using the Principled BSDF, the resulting graph is very usable. However, when using some of the other BSDFs, some of the generated shading graphs are difficult for other DCC's to understand.

Convert World Material

Convert the world material to a USD dome light. Currently works for simple materials, consisting of an environment texture connected to a background shader, with an optional vector multiply of the texture color.

Xuất Khẩu Chất Liệu (Export Textures)

Method for exporting textures.

Keep:

Use original location of textures.

Bảo Tồn (Preserve):

Preserve file paths of textures from already imported USD files. Export remaining textures to a 'textures' folder next to the USD file.

New Path:

Export textures to a 'textures' folder next to the USD file.

Viết Đè Chất Liệu (Overwrite Textures)

Cho phép viết đè lên các tập tin chất liệu hiện có khi xuất khẩu chất liệu.

USDZ Texture Downsampling

Choose a maximum size for all exported textures.

Keep:

Keep all current texture sizes.

256:

Resize to a maximum of 256 pixels.

512:

Resize to a maximum of 512 pixels.

1024:

Resize to a maximum of 1024 pixels.

2048:

Resize to a maximum of 2048 pixels.

4096:

Resize to a maximum of 4096 pixels.

Tùy Chỉnh (Custom):

Specify a custom size.

USDZ Custom Downscale Size

The size in pixels of the Custom downsampling.

Thử Nghiệm (Experimental)

Thực Thể Hóa (Instancing)

As this is an experimental option. When unchecked, duplicated objects are exported as real objects, so a particle system with 100 particles that is displayed with 100 meshes will have 100 individual meshes in the exported file. When checked, duplicated objects are exported as a reference to the original object. If the original object is not part of the export, the first duplicate is exported as real object and used as reference.

Những Giới Hạn của Trình Xuất Khẩu (Exporter Limitations)

Khung Lưới Một Mặt Bên và Hai Mặt (Single-sided and Double-sided Meshes)

USD seems to support neither per-material nor per-face-group double-sidedness, so Blender uses the flag from the first material to mark the entire mesh as single/double-sided. If there is no material it defaults to double-sided.

Các Pháp Tuyến của Khung Lưới (Mesh Normals)

The mesh subdivision scheme in USD is 'Catmull-Clark' by default, but Blender uses 'None' instead, indicating that a polygonal mesh is exported. This is necessary for USD to understand the custom normals; otherwise the mesh is always rendered smooth.

Tốc Lực của Điểm Đỉnh (Vertex Velocities)

Currently only fluid simulations (not meshes in general) have explicit vertex velocities. This is the most important case for exporting velocities, though, as the baked mesh changes topology all the time, and thus computing the velocities at import time in a post-processing step is hard.

Nguyên Vật Liệu (Materials)

When there are multiple materials, the mesh faces are stored as geometry subset and each material is assigned to the appropriate subset. If there is only one material this is skipped. Note that the geometry subsets are not time-sampled, so it may break when an animated mesh changes topology.

Tóc/Lông (Hair)

Only the parent strands are exported, and only with a constant color. No UV coordinates, and no information about the normals.

Máy Quay Phim (Camera)

Only perspective cameras are exported.

Nguồn Ánh Sáng (Lights)

USD does not directly support spot lights, so those are not exported.

Hạt (Particles)

Particles are only written when they are alive, which means that they are always visible. There is currently no code that deals with marking them as invisible outside their lifespan.

Objects instanced by particle system are exported by suffixing the object name with the particle's persistent ID, giving each particle transform a unique name.

Thực Thể Hóa/Tham Chiếu Hóa (Instancing/Referencing)

This is still an experimental feature that can be enabled when exporting to USD. When enabled, instanced object meshes are written to USD as references to the original mesh. The first copy of the mesh is written for real, and the following copies are referencing the first. Which mesh is considered 'the first' is chosen more or less arbitrarily.

USDZ

Due to a current limitation in the USD library, UDIM textures cannot be include in the USDZ archive. This limitation will likely be addressed in a future version of USD. (See USD pull request #2133.)