Commit Graph

19 Commits

Author SHA1 Message Date
atlv
75f49bd335
Move IrradianceVolume to bevy_light (#20000)
# Objective

- Reunite it with its family

## Solution

- Immigration

## Testing

- irradiance_volumes example
2025-07-07 20:11:43 +00:00
atlv
537adcc3f7
bevy_light (#19991)
# Objective

- make lights usable without bevy_render

## Solution

- make a new crate for lights to live in

## Testing

- 3d_scene, lighting, volumetric_fog, ssr, transmission, pcss,
light_textures

Note: no breaking changes because of re-exports, except for light
textures, which were introduced this cycle so it doesn't matter anyways
2025-07-07 00:07:38 +00:00
Kevin Reid
ce3db843bc
Make IrradianceVolume require LightProbe (and document this). (#19621)
## Objective

Make it easier to use `IrradianceVolume` with fewer ways to silently
fail. Fix #19614.

## Solution

* Add `#[require(LightProbe)]` to `struct IrradianceVolume`.
* Document this fact.
* Also document the volume being centered on the origin by default (this
was the other thing that was unclear when getting started).

I also looked at the other implementor of `LightProbeComponent`,
`EnvironmentMapLight`, but it has a use which is *not* as a light probe,
so it should not require `LightProbe`.

## Testing

* Confirmed that `examples/3d/irradiance_volumes.rs` still works after
removing `LightProbe`.
* Reviewed generated documentation.
2025-06-13 17:09:31 +00:00
andriyDev
b866bb4254
Remove Shader weak_handles from bevy_pbr (excluding meshlets). (#19365)
# Objective

- Related to #19024

## Solution

- Use the new `load_shader_library` macro for the shader libraries and
`embedded_asset`/`load_embedded_asset` for the "shader binaries" in
`bevy_pbr` (excluding meshlets).

## Testing

- `atmosphere` example still works
- `fog` example still works
- `decal` example still works

P.S. I don't think this needs a migration guide. Technically users could
be using the `pub` weak handles, but there's no actual good use for
them, so omitting it seems fine. Alternatively, we could mix this in
with the migration guide notes for #19137.
2025-05-27 22:32:47 +00:00
Gino Valente
9b32e09551
bevy_reflect: Add clone registrations project-wide (#18307)
# Objective

Now that #13432 has been merged, it's important we update our reflected
types to properly opt into this feature. If we do not, then this could
cause issues for users downstream who want to make use of
reflection-based cloning.

## Solution

This PR is broken into 4 commits:

1. Add `#[reflect(Clone)]` on all types marked `#[reflect(opaque)]` that
are also `Clone`. This is mandatory as these types would otherwise cause
the cloning operation to fail for any type that contains it at any
depth.
2. Update the reflection example to suggest adding `#[reflect(Clone)]`
on opaque types.
3. Add `#[reflect(clone)]` attributes on all fields marked
`#[reflect(ignore)]` that are also `Clone`. This prevents the ignored
field from causing the cloning operation to fail.
   
Note that some of the types that contain these fields are also `Clone`,
and thus can be marked `#[reflect(Clone)]`. This makes the
`#[reflect(clone)]` attribute redundant. However, I think it's safer to
keep it marked in the case that the `Clone` impl/derive is ever removed.
I'm open to removing them, though, if people disagree.
4. Finally, I added `#[reflect(Clone)]` on all types that are also
`Clone`. While not strictly necessary, it enables us to reduce the
generated output since we can just call `Clone::clone` directly instead
of calling `PartialReflect::reflect_clone` on each variant/field. It
also means we benefit from any optimizations or customizations made in
the `Clone` impl, including directly dereferencing `Copy` values and
increasing reference counters.

Along with that change I also took the liberty of adding any missing
registrations that I saw could be applied to the type as well, such as
`Default`, `PartialEq`, and `Hash`. There were hundreds of these to
edit, though, so it's possible I missed quite a few.

That last commit is **_massive_**. There were nearly 700 types to
update. So it's recommended to review the first three before moving onto
that last one.

Additionally, I can break the last commit off into its own PR or into
smaller PRs, but I figured this would be the easiest way of doing it
(and in a timely manner since I unfortunately don't have as much time as
I used to for code contributions).

## Testing

You can test locally with a `cargo check`:

```
cargo check --workspace --all-features
```
2025-03-17 18:32:35 +00:00
Alice Cecile
2ad5908e58
Make Query::single (and friends) return a Result (#18082)
# Objective

As discussed in #14275, Bevy is currently too prone to panic, and makes
the easy / beginner-friendly way to do a large number of operations just
to panic on failure.

This is seriously frustrating in library code, but also slows down
development, as many of the `Query::single` panics can actually safely
be an early return (these panics are often due to a small ordering issue
or a change in game state.

More critically, in most "finished" products, panics are unacceptable:
any unexpected failures should be handled elsewhere. That's where the
new

With the advent of good system error handling, we can now remove this.

Note: I was instrumental in a) introducing this idea in the first place
and b) pushing to make the panicking variant the default. The
introduction of both `let else` statements in Rust and the fancy system
error handling work in 0.16 have changed my mind on the right balance
here.

## Solution

1. Make `Query::single` and `Query::single_mut` (and other random
related methods) return a `Result`.
2. Handle all of Bevy's internal usage of these APIs.
3. Deprecate `Query::get_single` and friends, since we've moved their
functionality to the nice names.
4. Add detailed advice on how to best handle these errors.

Generally I like the diff here, although `get_single().unwrap()` in
tests is a bit of a downgrade.

## Testing

I've done a global search for `.single` to track down any missed
deprecated usages.

As to whether or not all the migrations were successful, that's what CI
is for :)

## Future work

~~Rename `Query::get_single` and friends to `Query::single`!~~

~~I've opted not to do this in this PR, and smear it across two releases
in order to ease the migration. Successive deprecations are much easier
to manage than the semantics and types shifting under your feet.~~

Cart has convinced me to change my mind on this; see
https://github.com/bevyengine/bevy/pull/18082#discussion_r1974536085.

## Migration guide

`Query::single`, `Query::single_mut` and their `QueryState` equivalents
now return a `Result`. Generally, you'll want to:

1. Use Bevy 0.16's system error handling to return a `Result` using the
`?` operator.
2. Use a `let else Ok(data)` block to early return if it's an expected
failure.
3. Use `unwrap()` or `Ok` destructuring inside of tests.

The old `Query::get_single` (etc) methods which did this have been
deprecated.
2025-03-02 19:51:56 +00:00
Zachary Harrold
5241e09671
Upgrade to Rust Edition 2024 (#17967)
# Objective

- Fixes #17960

## Solution

- Followed the [edition upgrade
guide](https://doc.rust-lang.org/edition-guide/editions/transitioning-an-existing-project-to-a-new-edition.html)

## Testing

- CI

---

## Summary of Changes

### Documentation Indentation

When using lists in documentation, proper indentation is now linted for.
This means subsequent lines within the same list item must start at the
same indentation level as the item.

```rust
/* Valid */
/// - Item 1
///   Run-on sentence.
/// - Item 2
struct Foo;

/* Invalid */
/// - Item 1
///     Run-on sentence.
/// - Item 2
struct Foo;
```

### Implicit `!` to `()` Conversion

`!` (the never return type, returned by `panic!`, etc.) no longer
implicitly converts to `()`. This is particularly painful for systems
with `todo!` or `panic!` statements, as they will no longer be functions
returning `()` (or `Result<()>`), making them invalid systems for
functions like `add_systems`. The ideal fix would be to accept functions
returning `!` (or rather, _not_ returning), but this is blocked on the
[stabilisation of the `!` type
itself](https://doc.rust-lang.org/std/primitive.never.html), which is
not done.

The "simple" fix would be to add an explicit `-> ()` to system
signatures (e.g., `|| { todo!() }` becomes `|| -> () { todo!() }`).
However, this is _also_ banned, as there is an existing lint which (IMO,
incorrectly) marks this as an unnecessary annotation.

So, the "fix" (read: workaround) is to put these kinds of `|| -> ! { ...
}` closuers into variables and give the variable an explicit type (e.g.,
`fn()`).

```rust
// Valid
let system: fn() = || todo!("Not implemented yet!");
app.add_systems(..., system);

// Invalid
app.add_systems(..., || todo!("Not implemented yet!"));
```

### Temporary Variable Lifetimes

The order in which temporary variables are dropped has changed. The
simple fix here is _usually_ to just assign temporaries to a named
variable before use.

### `gen` is a keyword

We can no longer use the name `gen` as it is reserved for a future
generator syntax. This involved replacing uses of the name `gen` with
`r#gen` (the raw-identifier syntax).

### Formatting has changed

Use statements have had the order of imports changed, causing a
substantial +/-3,000 diff when applied. For now, I have opted-out of
this change by amending `rustfmt.toml`

```toml
style_edition = "2021"
```

This preserves the original formatting for now, reducing the size of
this PR. It would be a simple followup to update this to 2024 and run
`cargo fmt`.

### New `use<>` Opt-Out Syntax

Lifetimes are now implicitly included in RPIT types. There was a handful
of instances where it needed to be added to satisfy the borrow checker,
but there may be more cases where it _should_ be added to avoid
breakages in user code.

### `MyUnitStruct { .. }` is an invalid pattern

Previously, you could match against unit structs (and unit enum
variants) with a `{ .. }` destructuring. This is no longer valid.

### Pretty much every use of `ref` and `mut` are gone

Pattern binding has changed to the point where these terms are largely
unused now. They still serve a purpose, but it is far more niche now.

### `iter::repeat(...).take(...)` is bad

New lint recommends using the more explicit `iter::repeat_n(..., ...)`
instead.

## Migration Guide

The lifetimes of functions using return-position impl-trait (RPIT) are
likely _more_ conservative than they had been previously. If you
encounter lifetime issues with such a function, please create an issue
to investigate the addition of `+ use<...>`.

## Notes

- Check the individual commits for a clearer breakdown for what
_actually_ changed.

---------

Co-authored-by: François Mockers <francois.mockers@vleue.com>
2025-02-24 03:54:47 +00:00
Sludge
989f547080
Weak handle migration (#17695)
# Objective

- Make use of the new `weak_handle!` macro added in
https://github.com/bevyengine/bevy/pull/17384

## Solution

- Migrate bevy from `Handle::weak_from_u128` to the new `weak_handle!`
macro that takes a random UUID
- Deprecate `Handle::weak_from_u128`, since there are no remaining use
cases that can't also be addressed by constructing the type manually

## Testing

- `cargo run -p ci -- test`

---

## Migration Guide

Replace `Handle::weak_from_u128` with `weak_handle!` and a random UUID.
2025-02-05 22:44:20 +00:00
Patrick Walton
6a4e0c801e
Fix several regressions from recent rendering changes. (#16890)
This commit fixes the following regressions:

1. Transmission-specific calls to shader lighting functions didn't pass
the `enable_diffuse` parameter, breaking the `transmission` example.

2. The combination of bindless `StandardMaterial` and bindless lightmaps
caused us to blow past the 128 texture limit on M1/M2 chips in some
cases, in particular the `depth_of_field` example.
https://github.com/gfx-rs/wgpu/issues/3334 should fix this, but in the
meantime this patch reduces the number of bindless lightmaps from 16 to
4 in order to stay under the limit.

3. The renderer was crashing on startup on Adreno 610 chips. This PR
simply disables bindless on Adreno 610 and lower.
2024-12-22 23:03:06 +00:00
Patrick Walton
bf3692a011
Introduce support for mixed lighting by allowing lights to opt out of contributing diffuse light to lightmapped objects. (#16761)
This PR adds support for *mixed lighting* to Bevy, whereby some parts of
the scene are lightmapped, while others take part in real-time lighting.
(Here *real-time lighting* means lighting at runtime via the PBR shader,
as opposed to precomputed light using lightmaps.) It does so by adding a
new field, `affects_lightmapped_meshes` to `IrradianceVolume` and
`AmbientLight`, and a corresponding field
`affects_lightmapped_mesh_diffuse` to `DirectionalLight`, `PointLight`,
`SpotLight`, and `EnvironmentMapLight`. By default, this value is set to
true; when set to false, the light contributes nothing to the diffuse
irradiance component to meshes with lightmaps.

Note that specular light is unaffected. This is because the correct way
to bake specular lighting is *directional lightmaps*, which we have no
support for yet.

There are two general ways I expect this field to be used:

1. When diffuse indirect light is baked into lightmaps, irradiance
volumes and reflection probes shouldn't contribute any diffuse light to
the static geometry that has a lightmap. That's because the baking tool
should have already accounted for it, and in a higher-quality fashion,
as lightmaps typically offer a higher effective texture resolution than
the light probe does.

2. When direct diffuse light is baked into a lightmap, punctual lights
shouldn't contribute any diffuse light to static geometry with a
lightmap, to avoid double-counting. It may seem odd to bake *direct*
light into a lightmap, as opposed to indirect light. But there is a use
case: in a scene with many lights, avoiding light leaks requires shadow
mapping, which quickly becomes prohibitive when many lights are
involved. Baking lightmaps allows light leaks to be eliminated on static
geometry.

A new example, `mixed_lighting`, has been added. It demonstrates a sofa
(model from the [glTF Sample Assets]) that has been lightmapped offline
using [Bakery]. It has four modes:

1. In *baked* mode, all objects are locked in place, and all the diffuse
direct and indirect light has been calculated ahead of time. Note that
the bottom of the sphere has a red tint from the sofa, illustrating that
the baking tool captured indirect light for it.

2. In *mixed direct* mode, lightmaps capturing diffuse direct and
indirect light have been pre-calculated for the static objects, but the
dynamic sphere has real-time lighting. Note that, because the diffuse
lighting has been entirely pre-calculated for the scenery, the dynamic
sphere casts no shadow. In a real app, you would typically use real-time
lighting for the most important light so that dynamic objects can shadow
the scenery and relegate baked lighting to the less important lights for
which shadows aren't as important. Also note that there is no red tint
on the sphere, because there is no global illumination applied to it. In
an actual game, you could fix this problem by supplementing the
lightmapped objects with an irradiance volume.

3. In *mixed indirect* mode, all direct light is calculated in
real-time, and the static objects have pre-calculated indirect lighting.
This corresponds to the mode that most applications are expected to use.
Because direct light on the scenery is computed dynamically, shadows are
fully supported. As in mixed direct mode, there is no global
illumination on the sphere; in a real application, irradiance volumes
could be used to supplement the lightmaps.

4. In *real-time* mode, no lightmaps are used at all, and all punctual
lights are rendered in real-time. No global illumination exists.

In the example, you can click around to move the sphere, unless you're
in baked mode, in which case the sphere must be locked in place to be
lit correctly.

## Showcase

Baked mode:
![Screenshot 2024-12-13
112926](https://github.com/user-attachments/assets/cc00d84e-abd7-4117-97e9-17267d815c6a)

Mixed direct mode:
![Screenshot 2024-12-13
112933](https://github.com/user-attachments/assets/49997305-349a-4f6a-b451-8cccbb469889)

Mixed indirect mode (default):
![Screenshot 2024-12-13
112939](https://github.com/user-attachments/assets/0f4f6d8a-998f-474b-9fa5-fe4c212c921c)

Real-time mode:
![Screenshot 2024-12-13
112944](https://github.com/user-attachments/assets/fdbc4535-d902-4ba0-bfbc-f5c7b723fac8)

## Migration guide

* The `AmbientLight` resource, the `IrradianceVolume` component, and the
`EnvironmentMapLight` component now have `affects_lightmapped_meshes`
fields. If you don't need to use that field (for example, if you aren't
using lightmaps), you can safely set the field to true.
* `DirectionalLight`, `PointLight`, and `SpotLight` now have
`affects_lightmapped_mesh_diffuse` fields. If you don't need to use that
field (for example, if you aren't using lightmaps), you can safely set
the field to true.

[glTF Sample Assets]:
https://github.com/KhronosGroup/glTF-Sample-Assets/tree/main

[Bakery]:
https://geom.io/bakery/wiki/index.php?title=Bakery_-_GPU_Lightmapper
2024-12-16 23:48:33 +00:00
Benjamin Brienen
40640fdf42
Don't reëxport bevy_image from bevy_render (#16163)
# Objective

Fixes #15940

## Solution

Remove the `pub use` and fix the compile errors.
Make `bevy_image` available as `bevy::image`.

## Testing

Feature Frenzy would be good here! Maybe I'll learn how to use it if I
have some time this weekend, or maybe a reviewer can use it.

## Migration Guide

Use `bevy_image` instead of `bevy_render::texture` items.

---------

Co-authored-by: chompaa <antony.m.3012@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2024-11-10 06:54:38 +00:00
Zachary Harrold
d70595b667
Add core and alloc over std Lints (#15281)
# Objective

- Fixes #6370
- Closes #6581

## Solution

- Added the following lints to the workspace:
  - `std_instead_of_core`
  - `std_instead_of_alloc`
  - `alloc_instead_of_core`
- Used `cargo +nightly fmt` with [item level use
formatting](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=#Item%5C%3A)
to split all `use` statements into single items.
- Used `cargo clippy --workspace --all-targets --all-features --fix
--allow-dirty` to _attempt_ to resolve the new linting issues, and
intervened where the lint was unable to resolve the issue automatically
(usually due to needing an `extern crate alloc;` statement in a crate
root).
- Manually removed certain uses of `std` where negative feature gating
prevented `--all-features` from finding the offending uses.
- Used `cargo +nightly fmt` with [crate level use
formatting](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=#Crate%5C%3A)
to re-merge all `use` statements matching Bevy's previous styling.
- Manually fixed cases where the `fmt` tool could not re-merge `use`
statements due to conditional compilation attributes.

## Testing

- Ran CI locally

## Migration Guide

The MSRV is now 1.81. Please update to this version or higher.

## Notes

- This is a _massive_ change to try and push through, which is why I've
outlined the semi-automatic steps I used to create this PR, in case this
fails and someone else tries again in the future.
- Making this change has no impact on user code, but does mean Bevy
contributors will be warned to use `core` and `alloc` instead of `std`
where possible.
- This lint is a critical first step towards investigating `no_std`
options for Bevy.

---------

Co-authored-by: François Mockers <francois.mockers@vleue.com>
2024-09-27 00:59:59 +00:00
Clar Fon
efda7f3f9c
Simpler lint fixes: makes ci lints work but disables a lint for now (#15376)
Takes the first two commits from #15375 and adds suggestions from this
comment:
https://github.com/bevyengine/bevy/pull/15375#issuecomment-2366968300

See #15375 for more reasoning/motivation.

## Rebasing (rerunning)

```rust
git switch simpler-lint-fixes
git reset --hard main
cargo fmt --all -- --unstable-features --config normalize_comments=true,imports_granularity=Crate
cargo fmt --all
git add --update
git commit --message "rustfmt"
cargo clippy --workspace --all-targets --all-features --fix
cargo fmt --all -- --unstable-features --config normalize_comments=true,imports_granularity=Crate
cargo fmt --all
git add --update
git commit --message "clippy"
git cherry-pick e6c0b94f6795222310fb812fa5c4512661fc7887
```
2024-09-24 11:42:59 +00:00
Blazepaws
b6b28a621f
Reflect derived traits on all components and resources: bevy_pbr (#15224)
Solves https://github.com/bevyengine/bevy/issues/15187 for bevy_pbr
2024-09-15 16:07:30 +00:00
Zachary Harrold
bc13161416
Migrated NonZero* to NonZero<*> (#14978)
# Objective

- Fixes #14974

## Solution

- Replace all* instances of `NonZero*` with `NonZero<*>`

## Testing

- CI passed locally.

---

## Notes

Within the `bevy_reflect` implementations for `std` types,
`impl_reflect_value!()` will continue to use the type aliases instead,
as it inappropriately parses the concrete type parameter as a generic
argument. If the `ZeroablePrimitive` trait was stable, or the macro
could be modified to accept a finite list of types, then we could fully
migrate.
2024-08-30 02:37:47 +00:00
Jan Hohenheim
6273227e09
Fix lints introduced in Rust beta 1.80 (#13899)
Resolves #13895

Mostly just involves being more explicit about which parts of the docs
belong to a list and which begin a new paragraph.
- found a few docs that were malformed because of exactly this, so I
fixed that by introducing a paragraph
- added indentation to nearly all multiline lists
- fixed a few minor typos
- added `#[allow(dead_code)]` to types that are needed to test
annotations but are never constructed
([here](https://github.com/bevyengine/bevy/pull/13899/files#diff-b02b63604e569c8577c491e7a2030d456886d8f6716eeccd46b11df8aac75dafR1514)
and
[here](https://github.com/bevyengine/bevy/pull/13899/files#diff-b02b63604e569c8577c491e7a2030d456886d8f6716eeccd46b11df8aac75dafR1523))
- verified that  `cargo +beta run -p ci -- lints` passes
- verified that `cargo +beta run -p ci -- test` passes
2024-06-17 17:22:01 +00:00
Robert Swain
ab7cbfa8fc
Consolidate Render(Ui)Materials(2d) into RenderAssets (#12827)
# Objective

- Replace `RenderMaterials` / `RenderMaterials2d` / `RenderUiMaterials`
with `RenderAssets` to enable implementing changes to one thing,
`RenderAssets`, that applies to all use cases rather than duplicating
changes everywhere for multiple things that should be one thing.
- Adopts #8149 

## Solution

- Make RenderAsset generic over the destination type rather than the
source type as in #8149
- Use `RenderAssets<PreparedMaterial<M>>` etc for render materials

---

## Changelog

- Changed:
- The `RenderAsset` trait is now implemented on the destination type.
Its `SourceAsset` associated type refers to the type of the source
asset.
- `RenderMaterials`, `RenderMaterials2d`, and `RenderUiMaterials` have
been replaced by `RenderAssets<PreparedMaterial<M>>` and similar.

## Migration Guide

- `RenderAsset` is now implemented for the destination type rather that
the source asset type. The source asset type is now the `RenderAsset`
trait's `SourceAsset` associated type.
2024-04-09 13:26:34 +00:00
Patrick Walton
3058c17d6a
Disable irradiance volumes on WebGL and WebGPU. (#11909)
They cause the number of texture bindings to overflow on those
platforms. Ultimately, we shouldn't unconditionally disable them, but
this fixes a crash blocking 0.13.

Closes #11885.
2024-02-17 01:49:46 +00:00
Patrick Walton
4c15dd0fc5
Implement irradiance volumes. (#10268)
# Objective

Bevy could benefit from *irradiance volumes*, also known as *voxel
global illumination* or simply as light probes (though this term is not
preferred, as multiple techniques can be called light probes).
Irradiance volumes are a form of baked global illumination; they work by
sampling the light at the centers of each voxel within a cuboid. At
runtime, the voxels surrounding the fragment center are sampled and
interpolated to produce indirect diffuse illumination.

## Solution

This is divided into two sections. The first is copied and pasted from
the irradiance volume module documentation and describes the technique.
The second part consists of notes on the implementation.

### Overview

An *irradiance volume* is a cuboid voxel region consisting of
regularly-spaced precomputed samples of diffuse indirect light. They're
ideal if you have a dynamic object such as a character that can move
about
static non-moving geometry such as a level in a game, and you want that
dynamic object to be affected by the light bouncing off that static
geometry.

To use irradiance volumes, you need to precompute, or *bake*, the
indirect
light in your scene. Bevy doesn't currently come with a way to do this.
Fortunately, [Blender] provides a [baking tool] as part of the Eevee
renderer, and its irradiance volumes are compatible with those used by
Bevy.
The [`bevy-baked-gi`] project provides a tool, `export-blender-gi`, that
can
extract the baked irradiance volumes from the Blender `.blend` file and
package them up into a `.ktx2` texture for use by the engine. See the
documentation in the `bevy-baked-gi` project for more details as to this
workflow.

Like all light probes in Bevy, irradiance volumes are 1×1×1 cubes that
can
be arbitrarily scaled, rotated, and positioned in a scene with the
[`bevy_transform::components::Transform`] component. The 3D voxel grid
will
be stretched to fill the interior of the cube, and the illumination from
the
irradiance volume will apply to all fragments within that bounding
region.

Bevy's irradiance volumes are based on Valve's [*ambient cubes*] as used
in
*Half-Life 2* ([Mitchell 2006], slide 27). These encode a single color
of
light from the six 3D cardinal directions and blend the sides together
according to the surface normal.

The primary reason for choosing ambient cubes is to match Blender, so
that
its Eevee renderer can be used for baking. However, they also have some
advantages over the common second-order spherical harmonics approach:
ambient cubes don't suffer from ringing artifacts, they are smaller (6
colors for ambient cubes as opposed to 9 for spherical harmonics), and
evaluation is faster. A smaller basis allows for a denser grid of voxels
with the same storage requirements.

If you wish to use a tool other than `export-blender-gi` to produce the
irradiance volumes, you'll need to pack the irradiance volumes in the
following format. The irradiance volume of resolution *(Rx, Ry, Rz)* is
expected to be a 3D texture of dimensions *(Rx, 2Ry, 3Rz)*. The
unnormalized
texture coordinate *(s, t, p)* of the voxel at coordinate *(x, y, z)*
with
side *S* ∈ *{-X, +X, -Y, +Y, -Z, +Z}* is as follows:

```text
s = x

t = y + ⎰  0 if S ∈ {-X, -Y, -Z}
        ⎱ Ry if S ∈ {+X, +Y, +Z}

        ⎧   0 if S ∈ {-X, +X}
p = z + ⎨  Rz if S ∈ {-Y, +Y}
        ⎩ 2Rz if S ∈ {-Z, +Z}
```

Visually, in a left-handed coordinate system with Y up, viewed from the
right, the 3D texture looks like a stacked series of voxel grids, one
for
each cube side, in this order:

| **+X** | **+Y** | **+Z** |
| ------ | ------ | ------ |
| **-X** | **-Y** | **-Z** |

A terminology note: Other engines may refer to irradiance volumes as
*voxel
global illumination*, *VXGI*, or simply as *light probes*. Sometimes
*light
probe* refers to what Bevy calls a reflection probe. In Bevy, *light
probe*
is a generic term that encompasses all cuboid bounding regions that
capture
indirect illumination, whether based on voxels or not.

Note that, if binding arrays aren't supported (e.g. on WebGPU or WebGL
2),
then only the closest irradiance volume to the view will be taken into
account during rendering.

[*ambient cubes*]:
https://advances.realtimerendering.com/s2006/Mitchell-ShadingInValvesSourceEngine.pdf

[Mitchell 2006]:
https://advances.realtimerendering.com/s2006/Mitchell-ShadingInValvesSourceEngine.pdf

[Blender]: http://blender.org/

[baking tool]:
https://docs.blender.org/manual/en/latest/render/eevee/render_settings/indirect_lighting.html

[`bevy-baked-gi`]: https://github.com/pcwalton/bevy-baked-gi

### Implementation notes

This patch generalizes light probes so as to reuse as much code as
possible between irradiance volumes and the existing reflection probes.
This approach was chosen because both techniques share numerous
similarities:

1. Both irradiance volumes and reflection probes are cuboid bounding
regions.
2. Both are responsible for providing baked indirect light.
3. Both techniques involve presenting a variable number of textures to
the shader from which indirect light is sampled. (In the current
implementation, this uses binding arrays.)
4. Both irradiance volumes and reflection probes require gathering and
sorting probes by distance on CPU.
5. Both techniques require the GPU to search through a list of bounding
regions.
6. Both will eventually want to have falloff so that we can smoothly
blend as objects enter and exit the probes' influence ranges. (This is
not implemented yet to keep this patch relatively small and reviewable.)

To do this, we generalize most of the methods in the reflection probes
patch #11366 to be generic over a trait, `LightProbeComponent`. This
trait is implemented by both `EnvironmentMapLight` (for reflection
probes) and `IrradianceVolume` (for irradiance volumes). Using a trait
will allow us to add more types of light probes in the future. In
particular, I highly suspect we will want real-time reflection planes
for mirrors in the future, which can be easily slotted into this
framework.

## Changelog

> This section is optional. If this was a trivial fix, or has no
externally-visible impact, you can delete this section.

### Added
* A new `IrradianceVolume` asset type is available for baked voxelized
light probes. You can bake the global illumination using Blender or
another tool of your choice and use it in Bevy to apply indirect
illumination to dynamic objects.
2024-02-06 23:23:20 +00:00