The Filament View that gets passed to tick() is retained briefly when
screenshots are enabled, but it may be destroyed by the time the
PixelBufferDescriptor callback is invoked. So, we needed a way of
notifying the AutomationEngine.
This adds a `material` key to `Settings`, as a sister to `view`.
Here's an example of an automation spec that manipulates material
parameters:
[{
"name": "metallic_vs_roughness",
"permute": {
"material.scalar.roughnessFactor": [0.0, 0.5, 1.0],
"material.scalar.metallicFactor": [0.0, 1.0]
}
}]
Currently this is limited to float, vec3, and vec4 parameters.
This adds `AutomationEngine` to libs/viewer, which iterates through
`Settings` instances that were generated from a JSON spec and applies
them to a Filament `View`. It can be configured to sleep between tests
using a time delay or a frame count.
This also adds command line arguments and user-interface elements to
`gltf_viewer` for automated testing.
This lets us generate long lists of settings permutations by writing a
simple JSON spec. For example, the following spec would generate six
`Settings` objects, all of which have SSAO enabled. See the unit test
for a larger example.
```
{
"name": "viewopts",
"base": { "view.ssao.enabled": true }
"permute": {
"view.dithering": ["NONE", "TEMPORAL"],
"view.sampleCount": [1, 4, 8]
}
}
```
This introduces the `viewer::Settings` struct, and a JSON reader /
writer.
This will be used for automated testing and for client / server
communication.
Note that `viewer::Settings` is closely associated with the
`filament::View` API; when updating the latter we will often need to
update the former, as well as some serialization code. This increases
the maintenance burden and I think we should consider using a parser
library like libclang or a macro-based reflection utility.
This PR also migrates SimpleViewer into libs/viewer and un-inlines its
implementation. It does not belong in gltfio because it has an imgui
dependency.
