This PR adds a WIP timeline UI for animating elements in the scene.
### Implemented Features
* The timeline can be panned with MMB and zoomed with Ctrl + Mouse Wheel
* The timeline can be "scrubbed" by dragging the red "play-head" with
LMB
* The timeline sidebar (displaying the list of tracks) can be resized by
dragging on the edge of the sidebar
* Keyframes can be added by pressing the "Add Keyframe" CTA in the UI
* Keyframes can be selected for editing by clicking the diamond-shaped
markers in the timeline
* Selected entities (including but not limited to keyframes) can be
deleted by pressing the "Delete" key
* Keyframes can be moved temporally by dragging the diamond-shaped
markers in the timeline
### Known issues
* Zooming the timeline in too far results in a soft-lock
* When zooming the timeline, the "transform origin" is currently
centered on the `00:00` timestamp. For ease of use, it should center on
the mouse cursor position instead.
* The timeline track-list is currently hard-coded to list the Camera and
Camera Target. Clicking on these entries currently serves no useful
purpose and may result in a crash.
* Keyframe markers in the timeline are not currently associated with
entries in the track-list and simply appear vertically centered in the
timeline view.
* Added keyframes currently record the position and orientation of the
scene camera when added, and are rendered in the world with debug
visualizations, but serve no useful purpose. Some design work is needed
(both user-experience and architectural) to decide on a workflow for
actually animating scene elements.
* Entity deletion cannot currently be undone/redone
This PR adds a `CanvasProviderElement` to `@storyteller/studio-web` to manage
the complexity of maintaining a single concrete `HTMLCanvasElement` for
`@storyteller/studio`, while still being able to treat components like the
`ViewerElement` as self-contained "views" that behave as expected with regards
to CSS styling, DOM placement, etc.
Consuming applications should wrap the new `<sts-canvas-provider />` element
around some common ancestor of all views into the `@storyteller/studio` app,
similar to a React context provider.
The `react-frontend` application has been updated to take advantage of the new
`CanvasProviderElement` by demonstrating a more realistic use case for the
`ViewerElement`. The new demo presents a grid of "thumbnails," one for each
object in our hard-coded "object library." Clicking on one of these thumbnails
will render a `ViewerElement` for that object in a modal dialog.
This PR adds the bones of a user-facing scene inspector.
### Work Done
To facilitate this work, the Bevy/frontend interface has been expanded to
accommodate two-way communications:
- The Bevy app can now dispatch JavaScript `CustomEvent`s via
`wasm::dispatch_to_js(...)`
- The frontend application can receive those events by listening for the given
event type on the `window` object
In its current state, the inspection system works by attaching the `Inspectable`
marker component to any entities which should be exposed to the user. A Bevy
system runs on `Update` to check for newly spawned or despawned entities with
that component, and emits events to notify the frontend. The frontend listens
for those events and updates its model of the scene accordingly, which is then
displayed with a simple tree view.
### Future Enhancements
There are many improvements that must be made to make this system actually
useful, but this PR is being expedited to focus on migrating to Bevy 0.12. A
shortlist of planned updates:
- Identify and expose the "type" of entity (e.g. lights, cameras, meshes,
skeletons, etc.) via a field on the `Inspectable` component
- Highlight the currently selected entity in the frontend hierarchy
- Ask the Bevy app to update the selection when the user selects an entry in the
hierarchy
- Add a separate UI panel to inspect and modify the selected entity's components
via the frontend
This PR adds functional transform gizmos, along with some new frontend UI to
configure their state.
## Work Done
- [x] Global / Local space toggling
- [x] Gizmo type toggling
- [x] Translation gizmo
- [x] Axis-constrained translation
- [x] Plane-constrained translation
- [x] Screen-space translation
- [x] Rotation gizmo
- [x] Axis-constrained rotation
- [x] Screen-space rotation
- [x] "Trackball" rotation
- [ ] Scale gizmo
- [ ] Single-axis non-uniform scaling
- [ ] Two-axis non-uniform scaling
- [ ] Uniform scaling
- [ ] Combination gizmos
- [x] Translation + Rotation
- [ ] Translation + Scale
- [ ] Rotation + Scale
- [ ] Translation + Rotation + Scale
## Future Enhancements
### Better visual feedback during transformations
Most DCCs update the visual representation of the transform gizmo while it's in
the process of being actively manipulated. (For example, Blender draws lines in
world-space to indicate that the transformation is constrained to a particular
axis or plane, hides widgets that aren't participating in the current
transformation, and illustrates the angle of difference between the original and
updated rotation.) At a minimum, we should indicate the current widget being
manipulated with a color change (like we already do when the widget is being
hovered). This requires a bit of additional state management effort but
shouldn't be overly difficult to add in a future PR.
### Better visual representation for rotation widgets
Currently, each axis of rotation is represented on the gizmo with a full-circle,
unlit "ring" shape. This can make it difficult to tell which half of the ring is
closer to the viewer, and thus to get an accurate understanding of how the
transform is currently oriented, without moving the camera around. A [previous
version of this work](#4) bisected the rings along a view-oriented plane and
rendered the "back-side" ring halves with reduced opacity. This PR uses static
meshes instead of an immediate-mode drawing API to render the gizmos, so a
custom shader would be the ideal way to reproduce that effect. That effort
should be deferred until after upgrading to Bevy 0.12, as it brings some changes
which would likely require some updates to that code.
### Better visual representation for translation arrows
A [previous version of this work](#4) faded the opacity of the translation
arrows when they were very close to parallel with the view direction — an idea
that was borrowed from Blender. It's a nice UX enhancement because translating
along an axis that's very close to parallel with the view direction can be janky
and error-prone, so it makes sense to disallow it and instead provide an
unobstructed view of the screen-space translation widget. This would also
require a custom shader, in addition to some extra state management logic (to
disable the widgets when their opacity is zeroed out). Given that it's only a
"nice-to-have," I think it makes sense to backlog this for the time being.
## Known Issues
### Picking
There's currently a bug in `bevy_mod_picking` that affects the hit-testing of
the gizmo widgets. The gizmos are currently _rendering_ on top of everything
else (via a second camera and render-layer configurations), but the picking
behavior doesn't take the rendering order into account. This means that portions
of the gizmo widgets which are occluded by geometry in the world cannot be
interacted with (because the occluding geometry interrupts the picking raycast).
> Update: This is fixed in the new release of `bevy_mod_picking` for Bevy 0.12.
### Delay on first-render
The first time a new widget shape is spawned, there's a noticeable delay (of 1
to several seconds) before the widget is rendered, during which the UI becomes
unresponsive. This is likely the same issue that triggers a much longer delay
when the glTF scene is being spawned. I'd like to see if Bevy 0.12 resolves or
mitigates this issue before addressing it on our end, but if it doesn't, I think
we can simply spawn an instance of each of the gizmo widgets off-screen on
application startup to prevent lag spikes from happening while a user is
interacting with the scene.
### Non-deterministic hover states
The widget colors are currently being updated by, e.g., multiplying on
mouser-over and dividing on mouse-out. Occasionally those events happen in quick
enough succession that our mouse-out listener is not invoked, so a widget gets
"stuck" in its hovered state. The fix for this is trivial but fairly annoying,
so I haven't gotten around to it yet. 🙂
> Update: This issue mostly occurs when in world-space mode. The gizmo is torn
> down and re-built from scratch once a drag event completes, which can despawn
> the gizmo while an element is still hovered. The solution will likely involve
> completely separate materials for default and hover states, similar to how
> `bevy_mod_picking`'s highlight plugin works.
### Object Selection
There's still some jank happening with object selection and camera orbiting, as
mentioned in #8. I don't anticipate this being overly difficult to resolve, but
I'm deferring that work until more of the core functionality is built out since
it's not a blocker for now.
### Skinned Mesh Selection
There's also still the issue of the skinned mesh being unselectable — which, it
turns out, is [technically not actually the
case](https://github.com/bevyengine/bevy/issues/4971). Rather, the picking
raycast "sees" the mesh as if it were still in its original rest pose, because
the mesh deformations are processed on the GPU and not reflected back to the
CPU-side representation.
I think the ideal workaround for this will be to attach capsule-shaped Rapier
colliders to the skeleton (similar to Unreal Engine's auto-generated "physics
assets" for skeletal meshes) and use those for picking instead. This would
automatically enable skeletal pose manipulation (by transforming the individual
joints), which is already a long term goal. It also makes more sense from a
practical standpoint, as the mesh itself cannot be independently transformed
while it's bound to the skeleton, so there's little point in directly selecting
it.
Danny McGee