* Fixes https://github.com/bevyengine/bevy/issues/13813
* Fixes https://github.com/bevyengine/bevy/issues/13810
Tested a combined scene with both regular meshes and meshlet meshes
with:
* Regular forward setup
* Forward + normal/motion vector prepasses
* Deferred (with depth prepass since that's required)
* Deferred + depth/normal/motion vector prepasses
Still broken:
* Using meshlet meshes rendering in deferred and regular meshes
rendering in forward + depth/normal prepass. I don't know how to fix
this at the moment, so for now I've just add instructions to not mix
them.
# Objective
- Add motion vector support to the skybox
- This fixes the last remaining "gap" to complete the motion blur
feature
## Solution
- Add a pipeline for the skybox to write motion vectors to the prepass
## Testing
- Used examples to test motion vectors using motion blur
https://github.com/bevyengine/bevy/assets/2632925/74c0778a-7e77-4e68-8111-05791e4bfdd2
---------
Co-authored-by: Patrick Walton <pcwalton@mimiga.net>
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
- Per-cluster (instance of a meshlet) data upload is ridiculously
expensive in both CPU and GPU time (8 bytes per cluster, millions of
clusters, you very quickly run into PCIE bandwidth maximums, and lots of
CPU-side copies and malloc).
- We need to be uploading only per-instance/entity data. Anything else
needs to be done on the GPU.
## Solution
- Per instance, upload:
- `meshlet_instance_meshlet_counts_prefix_sum` - An exclusive prefix sum
over the count of how many clusters each instance has.
- `meshlet_instance_meshlet_slice_starts` - The starting index of the
meshlets for each instance within the `meshlets` buffer.
- A new `fill_cluster_buffers` pass once at the start of the frame has a
thread per cluster, and finds its instance ID and meshlet ID via a
binary search of `meshlet_instance_meshlet_counts_prefix_sum` to find
what instance it belongs to, and then uses that plus
`meshlet_instance_meshlet_slice_starts` to find what number meshlet
within the instance it is. The shader then writes out the per-cluster
instance/meshlet ID buffers for later passes to quickly read from.
- I've gone from 45 -> 180 FPS in my stress test scene, and saved
~30ms/frame of overall CPU/GPU time.
# Objective
- Upload previous frame's inverse_view matrix to the GPU for use with
https://github.com/bevyengine/bevy/pull/12898.
---
## Changelog
- Added `prepass_bindings::previous_view_uniforms.inverse_view`.
- Renamed `prepass_bindings::previous_view_proj` to
`prepass_bindings::previous_view_uniforms.view_proj`.
- Renamed `PreviousViewProjectionUniformOffset` to
`PreviousViewUniformOffset`.
- Renamed `PreviousViewProjection` to `PreviousViewData`.
## Migration Guide
- Renamed `prepass_bindings::previous_view_proj` to
`prepass_bindings::previous_view_uniforms.view_proj`.
- Renamed `PreviousViewProjectionUniformOffset` to
`PreviousViewUniformOffset`.
- Renamed `PreviousViewProjection` to `PreviousViewData`.
