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Add `USD Preview Surface From Nodes` export option, to convert a
Principled BSDF material node network to an approximate USD Preview
Surface shader representation. If this option is disabled, the original
material export behavior is maintained, where viewport setting are saved
to the Preview Surface shader.
Also added the following options for texture export.
- `Export Textures`: If converting Preview Surface, export textures
referenced by shader nodes to a 'textures' directory which is a
sibling of the USD file.
- `Overwrite Textures`: Allow overwriting existing texture files when
exporting textures (this option is off by default).
- `Relative Texture Paths`: Make texture asset paths relative to the
USD.
The entry point for the new functionality is
`create_usd_preview_surface_material()`, called from
`USDAbstractWriter::ensure_usd_material()`. The material conversion
currently handles a small subset of Blender shading nodes,
`BSDF_DIFFUSE`, `BSDF_PRINCIPLED`, `TEX_IMAGE` and `UVMAP`.
Texture export is handled by copying texture files from their original
location to a `textures` folder in the same directory as the USD.
In-memory and packed textures are saved directly to the textures folder.
This patch is based, in part, on code in Tangent Animation's USD
exporter branch.
Reviewed By: sybren, HooglyBoogly
Differential Revision: https://developer.blender.org/D13647
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This is an initial implementation of a USD importer.
This work is comprised of Tangent Animation's open source USD importer,
combined with features @makowalski had implemented.
The design is very similar to the approach taken in the Alembic
importer. The core functionality resides in a collection of "reader"
classes, each of which is responsible for converting an instance of a
USD prim to the corresponding Blender Object representation.
The flow of control for the conversion can be followed in the
`import_startjob()` and `import_endjob()` functions in `usd_capi.cc`.
The `USDStageReader` class is responsible for traversing the USD stage
and instantiating the appropriate readers.
Reviewed By: sybren, HooglyBoogly
Differential Revision: https://developer.blender.org/D10700
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`WM_operator_properties_filesel()` allows C operators to set a display or sort
type for the File Browser to use. But the File Browser would always override
that because of an invalid `_is_set()` check. (The operators don't actually set
the value, they only set the property's default value.)
The only operator affected by this is "Recover Auto Save". It is supposed to
show a vertical list ordered chronologically. It used settings from the
previous File Browser usage before this patch.
Operators using the File Browser should generally use
`FILE_DEFAULTDISPLAY`/`FILE_SORT_DEFAULT` now, except if they have a reason not
to. See comments at their definition.
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This makes it so operators that set a different display or sort type
don't change the sort or display type for the next File Browser operation.
So using "Recover Auto Save" entirely isolates display and sort type from other
operations.
Differential Revision: https://developer.blender.org/D8598
Reviewed by: Bastien Montagne
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The fix for T75936 made it possible to export invisible objects to
Alembic. This commit applies the same approach to the USD exporter.
The USD and Alembic code is slightly different in terms of where in the
exported file the visibility attribute is stored. In USD the visibility
is used to prune the scene graph, and thus there are only two options:
"hidden" and "inherited". Setting the visiblity of a node in the scene
graph to "hidden" immediately hides all its children. To allow hidden
parents with visible children, the visibility is stored on the object
data (so the geometry/camera/lamp/etc) instead.
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Operators are one of the last places in Blender to use older UI designs
that don't fit in with recent style conventions. This commit updates
these custom operator UI callbacks for consistency and clarity.
Some of the code is also simplified a lot. Some of the older operator layouts
were much more complex (in terms of code) than they needed to be.
See the differential revision for a before and after screenshot
of each operator.
Differential Revision: https://developer.blender.org/D8326
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- "Only Export Selected Objects" → "Selection Only", as this is the
standard used in other exporters.
- "Evaluation Mode" → "Use Settings for", as this is clearer for users
who aren't as familiar with the technical details of the depsgraph.
- "Use Instancing" → "Instancing", and moved the checkbox to the end of
the option list into its own box "Experimental". This looks a bit
cleaner than just plonking "EXPERIMENTAL" in the checkbox label.
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Most options were 'Export …', now they are just '…'.
For example, 'Export UV Maps' → 'UV Maps'.
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The way the USD exporter currently works, it is not possible to export
invisible objects. As such, the 'Visible Objects Only' option was
confusing.
Exporting invisible objects means obtaining invisible evaluated objects
from the depsgraph, which is not something that's currently implemented.
Once that's done, we can reintroduce this option.
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There are options for the exporter that are relevant for each export, for
example the choice between Viewport or Render settings, or whether to
export the current frame or an animation. It's better to have the options
panel opened by default.
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This commit introduces the first version of an exporter to Pixar's
Universal Scene Description (USD) format.
Reviewed By: sergey, LazyDodo
Differential Revision: https://developer.blender.org/D6287
- The USD libraries are built by `make deps`, but not yet built by
install_deps.sh.
- Only experimental support for instancing; by default all duplicated
objects are made real in the USD file. This is fine for exporting a
linked-in posed character, not so much for thousands of pebbles etc.
- The way materials and UV coordinates and Normals are exported is going
to change soon.
- This patch contains LazyDodo's fixes for building on Windows in D5359.
== Meshes ==
USD seems to support neither per-material nor per-face-group
double-sidedness, so we just use the flag from the first non-empty
material slot. If there is no material we default to double-sidedness.
Each UV map is stored on the mesh in a separate primvar. Materials can
refer to these UV maps, but this is not yet exported by Blender. The
primvar name is the same as the UV Map name. This is to allow the
standard name "st" for texture coordinates by naming the UV Map as such,
without having to guess which UV Map is the "standard" one.
Face-varying mesh normals are written to USD. When the mesh has custom
loop normals those are written. Otherwise the poly flag `ME_SMOOTH` is
inspected to determine the normals.
The UV maps and mesh normals take up a significant amount of space, so
exporting them is optional. They're still enabled by default, though.
For comparison: a shot of Spring (03_035_A) is 1.2 GiB when exported
with UVs and normals, and 262 MiB without. We probably have room for
optimisation of written UVs and normals.
The mesh subdivision scheme isn't using the default value 'Catmull
Clark', but uses 'None', indicating we're exporting a polygonal mesh.
This is necessary for USD to understand our normals; otherwise the mesh
is always rendered smooth. In the future we may want to expose this
choice of subdivision scheme to the user, or auto-detect it when we
actually support exporting pre-subdivision meshes.
A possible optimisation could be to inspect whether all polygons are
smooth or flat, and mark the USD mesh as such. This can be added when
needed.
== Animation ==
Mesh and transform animation are now written when passing
`animation=True` to the export operator. There is no inspection of
whether an object is actually animated or not; USD can handle
deduplication of static values for us.
The administration of which timecode to use for the export is left to
the file-format-specific concrete subclasses of
`AbstractHierarchyIterator`; the abstract iterator itself doesn't know
anything about the passage of time. This will allow subclasses for the
frame-based USD format and time-based Alembic format.
== Support for simple preview materials ==
Very simple versions of the materials are now exported, using only the
viewport diffuse RGB, metallic, and roughness.
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.
The first material if any) is always applied to the mesh itself
(regardless of the existence of geometry subsets), because the Hydra
viewport doesn't support materials on subsets. See
https://github.com/PixarAnimationStudios/USD/issues/542 for more info.
Note that the geometry subsets are not yet time-sampled, so it may break
when an animated mesh changes topology.
Materials are exported as a flat list under a top-level '/_materials'
namespace. This inhibits instancing of the objects using those
materials, so this is subject to change.
== Hair ==
Only the parent strands are exported, and only with a constant colour.
No UV coordinates, no information about the normals.
== Camera ==
Only perspective cameras are supported for now.
== 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).
Particle-system-instanced objects are exported by suffixing the object
name with the particle's persistent ID, giving each particle XForm a
unique name.
== Instancing/referencing ==
This exporter has experimental support for instancing/referencing.
Dupli-object meshes are now written to USD as references to the original
mesh. This is still very limited in correctness, as there are issues
referencing to materials from a referenced mesh.
I am still committing this, as it gives us a place to start when
continuing the quest for proper instancing in USD.
== Lights ==
USD does not directly support spot lights, so those aren't exported yet.
It's possible to add this in the future via the UsdLuxShapingAPI. The
units used for the light intensity are also still a bit of a mystery.
== Fluid 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.
== The Building Process ==
- USD is built as monolithic library, instead of 25 smaller libraries.
We were linking all of them as 'whole archive' anyway, so this doesn't
affect the final file size. It does, however, make life easier with
respect to linking order, and handling upstream changes.
- The JSON files required by USD are installed into datafiles/usd; they
are required on every platform. Set the `PXR_PATH_DEBUG` to any value
to have the USD library print the paths it uses to find those files.
- USD is patched so that it finds the aforementioned JSON files in a path
that we pass to it from Blender.
- USD is patched to have a `PXR_BUILD_USD_TOOLS` CMake option to disable
building the tools in its `bin` directory. This is sent as a pull
request at https://github.com/PixarAnimationStudios/USD/pull/1048
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