# Objective
- Using bincode to deserialize binary into a MeshletMesh is expensive
(~77ms for a 5mb file).
## Solution
- Write a custom deserializer using bytemuck's Pod types and slice
casting.
- Total asset load time has gone from ~102ms to ~12ms.
- Change some types I never meant to be public to private and other misc
cleanup.
## Testing
- Ran the meshlet example and added timing spans to the asset loader.
---
## Changelog
- Improved `MeshletMesh` loading speed
- The `MeshletMesh` disk format has changed, and
`MESHLET_MESH_ASSET_VERSION` has been bumped
- `MeshletMesh` fields are now private
- Renamed `MeshletMeshSaverLoad` to `MeshletMeshSaverLoader`
- The `Meshlet`, `MeshletBoundingSpheres`, and `MeshletBoundingSphere`
types are now private
- Removed `MeshletMeshSaveOrLoadError::SerializationOrDeserialization`
- Added `MeshletMeshSaveOrLoadError::WrongFileType`
## Migration Guide
- Regenerate your `MeshletMesh` assets, as the disk format has changed,
and `MESHLET_MESH_ASSET_VERSION` has been bumped
- `MeshletMesh` fields are now private
- `MeshletMeshSaverLoad` is now named `MeshletMeshSaverLoader`
- The `Meshlet`, `MeshletBoundingSpheres`, and `MeshletBoundingSphere`
types are now private
- `MeshletMeshSaveOrLoadError::SerializationOrDeserialization` has been
removed
- Added `MeshletMeshSaveOrLoadError::WrongFileType`, match on this
variant if you match on `MeshletMeshSaveOrLoadError`
This commit, a revamp of #12959, implements screen-space reflections
(SSR), which approximate real-time reflections based on raymarching
through the depth buffer and copying samples from the final rendered
frame. This patch is a relatively minimal implementation of SSR, so as
to provide a flexible base on which to customize and build in the
future. However, it's based on the production-quality [raymarching code
by Tomasz
Stachowiak](https://gist.github.com/h3r2tic/9c8356bdaefbe80b1a22ae0aaee192db).
For a general basic overview of screen-space reflections, see
[1](https://lettier.github.io/3d-game-shaders-for-beginners/screen-space-reflection.html).
The raymarching shader uses the basic algorithm of tracing forward in
large steps, refining that trace in smaller increments via binary
search, and then using the secant method. No temporal filtering or
roughness blurring, is performed at all; for this reason, SSR currently
only operates on very shiny surfaces. No acceleration via the
hierarchical Z-buffer is implemented (though note that
https://github.com/bevyengine/bevy/pull/12899 will add the
infrastructure for this). Reflections are traced at full resolution,
which is often considered slow. All of these improvements and more can
be follow-ups.
SSR is built on top of the deferred renderer and is currently only
supported in that mode. Forward screen-space reflections are possible
albeit uncommon (though e.g. *Doom Eternal* uses them); however, they
require tracing from the previous frame, which would add complexity.
This patch leaves the door open to implementing SSR in the forward
rendering path but doesn't itself have such an implementation.
Screen-space reflections aren't supported in WebGL 2, because they
require sampling from the depth buffer, which Naga can't do because of a
bug (`sampler2DShadow` is incorrectly generated instead of `sampler2D`;
this is the same reason why depth of field is disabled on that
platform).
To add screen-space reflections to a camera, use the
`ScreenSpaceReflectionsBundle` bundle or the
`ScreenSpaceReflectionsSettings` component. In addition to
`ScreenSpaceReflectionsSettings`, `DepthPrepass` and `DeferredPrepass`
must also be present for the reflections to show up. The
`ScreenSpaceReflectionsSettings` component contains several settings
that artists can tweak, and also comes with sensible defaults.
A new example, `ssr`, has been added. It's loosely based on the
[three.js ocean
sample](https://threejs.org/examples/webgl_shaders_ocean.html), but all
the assets are original. Note that the three.js demo has no screen-space
reflections and instead renders a mirror world. In contrast to #12959,
this demo tests not only a cube but also a more complex model (the
flight helmet).
## Changelog
### Added
* Screen-space reflections can be enabled for very smooth surfaces by
adding the `ScreenSpaceReflections` component to a camera. Deferred
rendering must be enabled for the reflections to appear.
# Objective
- #12755 introduced the need to download a file to run an example
- This means the example fails to run in CI without downloading that
file
## Solution
- Add a new metadata to examples "setup" that provides setup
instructions
- Replace the URL in the meshlet example to one that can actually be
downloaded
- example-showcase execute the setup before running an example
Keeping track of explicit visibility per cluster between frames does not
work with LODs, and leads to worse culling (using the final depth buffer
from the previous frame is more accurate).
Instead, we need to generate a second depth pyramid after the second
raster pass, and then use that in the first culling pass in the next
frame to test if a cluster would have been visible last frame or not.
As part of these changes, the write_index_buffer pass has been folded
into the culling pass for a large performance gain, and to avoid
tracking a lot of extra state that would be needed between passes.
Prepass previous model/view stuff was adapted to work with meshlets as
well.
Also fixed a bug with materials, and other misc improvements.
---------
Co-authored-by: François <mockersf@gmail.com>
Co-authored-by: atlas dostal <rodol@rivalrebels.com>
Co-authored-by: vero <email@atlasdostal.com>
Co-authored-by: Patrick Walton <pcwalton@mimiga.net>
Co-authored-by: Robert Swain <robert.swain@gmail.com>
