bevy/crates/bevy_render
Patrick Walton 1141e731ff
Implement alpha to coverage (A2C) support. (#12970)
[Alpha to coverage] (A2C) replaces alpha blending with a
hardware-specific multisample coverage mask when multisample
antialiasing is in use. It's a simple form of [order-independent
transparency] that relies on MSAA. ["Anti-aliased Alpha Test: The
Esoteric Alpha To Coverage"] is a good summary of the motivation for and
best practices relating to A2C.

This commit implements alpha to coverage support as a new variant for
`AlphaMode`. You can supply `AlphaMode::AlphaToCoverage` as the
`alpha_mode` field in `StandardMaterial` to use it. When in use, the
standard material shader automatically applies the texture filtering
method from ["Anti-aliased Alpha Test: The Esoteric Alpha To Coverage"].
Objects with alpha-to-coverage materials are binned in the opaque pass,
as they're fully order-independent.

The `transparency_3d` example has been updated to feature an object with
alpha to coverage. Happily, the example was already using MSAA.

This is part of #2223, as far as I can tell.

[Alpha to coverage]: https://en.wikipedia.org/wiki/Alpha_to_coverage

[order-independent transparency]:
https://en.wikipedia.org/wiki/Order-independent_transparency

["Anti-aliased Alpha Test: The Esoteric Alpha To Coverage"]:
https://bgolus.medium.com/anti-aliased-alpha-test-the-esoteric-alpha-to-coverage-8b177335ae4f

---

## Changelog

### Added

* The `AlphaMode` enum now supports `AlphaToCoverage`, to provide
limited order-independent transparency when multisample antialiasing is
in use.
2024-04-15 20:37:52 +00:00
..
macros Consolidate Render(Ui)Materials(2d) into RenderAssets (#12827) 2024-04-09 13:26:34 +00:00
src Implement alpha to coverage (A2C) support. (#12970) 2024-04-15 20:37:52 +00:00
Cargo.toml Clean up some low level dependencies (#12858) 2024-04-08 19:45:42 +00:00