bevy/crates/bevy_pbr
JMS55 f4dab8a4e8
Multithreaded render command encoding (#9172)
# Objective
- Encoding many GPU commands (such as in a renderpass with many draws,
such as the main opaque pass) onto a `wgpu::CommandEncoder` is very
expensive, and takes a long time.
- To improve performance, we want to perform the command encoding for
these heavy passes in parallel.

## Solution
- `RenderContext` can now queue up "command buffer generation tasks"
which are closures that will generate a command buffer when called.
- When finalizing the render context to produce the final list of
command buffers, these tasks are run in parallel on the
`ComputeTaskPool` to produce their corresponding command buffers.
- The general idea is that the node graph will run in serial, but in a
node, instead of doing rendering work, you can add tasks to do render
work in parallel with other node's tasks that get ran at the end of the
graph execution.

## Nodes Parallelized
- `MainOpaquePass3dNode`
- `PrepassNode`
- `DeferredGBufferPrepassNode`
- `ShadowPassNode` (One task per view)


## Future Work
- For large number of draws calls, might be worth further subdividing
passes into 2+ tasks.
- Extend this to UI, 2d, transparent, and transmissive nodes?
- Needs testing - small command buffers are inefficient - it may be
worth reverting to the serial command encoder usage for render phases
with few items.
- All "serial" (traditional) rendering work must finish before parallel
rendering tasks (the new stuff) can start to run.
- There is still only one submission to the graphics queue at the end of
the graph execution. There is still no ability to submit work earlier.

## Performance Improvement
Thanks to @Elabajaba for testing on Bistro.


![image](https://github.com/bevyengine/bevy/assets/47158642/be50dafa-85eb-4da5-a5cd-c0a044f1e76f)


TLDR: Without shadow mapping, this PR has no impact. _With_ shadow
mapping, this PR gives **~40 more fps** than main.

---

## Changelog
- `MainOpaquePass3dNode`, `PrepassNode`, `DeferredGBufferPrepassNode`,
and each shadow map within `ShadowPassNode` are now encoded in parallel,
giving _greatly_ increased CPU performance, mainly when shadow mapping
is enabled.
  - Does not work on WASM or AMD+Windows+Vulkan.
- Added `RenderContext::add_command_buffer_generation_task()`.
- `RenderContext::new()` now takes adapter info
- Some render graph and Node related types and methods now have
additional lifetime constraints.


## Migration Guide
`RenderContext::new()` now takes adapter info
- Some render graph and Node related types and methods now have
additional lifetime constraints.

---------

Co-authored-by: Elabajaba <Elabajaba@users.noreply.github.com>
Co-authored-by: François <mockersf@gmail.com>
2024-02-09 07:35:35 +00:00
..
src Multithreaded render command encoding (#9172) 2024-02-09 07:35:35 +00:00
Cargo.toml Async pipeline compilation (#10812) 2024-02-05 13:50:50 +00:00