Prior to this change, `recomputeBoundingBoxes` was an opt-in config
parameter in ResourceLoader. It is now a method on FilamentInstance.
The old API did not work for dynamically created instances. Since this
is a relatively obscure feature, we considered removing it completely,
especially since the computation requires the presence of CPU-side
vertex data combined with the transform hierarchy.
Instead of removing the feature, we decided to move it to a better
place. This paves the way for some upcoming improvements, which include
reducing the memory footprint for assets. It also improves overall code
organization and separation of concerns.
This change was motivated by some internal work at Google and has the
benefit of simplifying the gltfio API and implementation. There are 2
major API changes:
(1) Consolidate separate loader entry points for GLB and GLTF.
The distinction between GLB and GLTF can be made from the file content
alone, because GLB has a 4-byte magic string in its header. There is no
need for separate entry points. Clients do not (and should not) need
to check the file name extension.
(2) Remove the distinction between "instanced" and "non-instanced"
glTF assets.
In the new scheme, all assets have at least 1 instance.
Broadly speaking, in gltfio an "asset" is a collection of Filament
objects like textures and vertex buffers, while an "instance" is a
collection of entities and components (e.g. the transform hierarchy).
This API change makes life easier for clients because they no longer
need to decide a priori if they will ever need to add instances.
This change also moves some public-facing methods from FilamentAsset to
FilamentInstance:
- getSkinCount, getSkinNameAt
- getJointCountAt, getJointsAt
- attachSkin, detachSkin
We still use resgen for convience, but the archive is now passed in
from the client application.
This will allow us to shrink the gltfio Android library (stay tuned).
An ubershader archive is a bundle of filamat packages with some metadata
that conveys which glTF features each material supports.
This PR does three things:
1. Adds a new command line tool called `uberz` that consumes a list
of filamat files and metadata text files and produces a single
ubershader archive.
2. Adds a new library (also called `uberz`) that is used by `gltfio`
to read ubershader archives, and used by the above command line
tool to write ubershader archives.
3. Enhances `UbershaderLoader` so that it no longers uses a hardcoded
set of materials, and instead takes an ubershader archive.
Ubershader archives have a simple binary layout that can be memcpy'd
directly into a C struct. The metadata is specified using a text file
with key-value pairs. These two file formats have formal desriptions in
the README in `libs/uberz`.
In a subsequent PR, we will remove the `gltfio_resources` target and
change the signature of `createUbershaderLoader` so that it takes
an archive.
