[*Percentage-closer soft shadows*] are a technique from 2004 that allow
shadows to become blurrier farther from the objects that cast them. It
works by introducing a *blocker search* step that runs before the normal
shadow map sampling. The blocker search step detects the difference
between the depth of the fragment being rasterized and the depth of the
nearby samples in the depth buffer. Larger depth differences result in a
larger penumbra and therefore a blurrier shadow.
To enable PCSS, fill in the `soft_shadow_size` value in
`DirectionalLight`, `PointLight`, or `SpotLight`, as appropriate. This
shadow size value represents the size of the light and should be tuned
as appropriate for your scene. Higher values result in a wider penumbra
(i.e. blurrier shadows).
When using PCSS, temporal shadow maps
(`ShadowFilteringMethod::Temporal`) are recommended. If you don't use
`ShadowFilteringMethod::Temporal` and instead use
`ShadowFilteringMethod::Gaussian`, Bevy will use the same technique as
`Temporal`, but the result won't vary over time. This produces a rather
noisy result. Doing better would likely require downsampling the shadow
map, which would be complex and slower (and would require PR #13003 to
land first).
In addition to PCSS, this commit makes the near Z plane for the shadow
map configurable on a per-light basis. Previously, it had been hardcoded
to 0.1 meters. This change was necessary to make the point light shadow
map in the example look reasonable, as otherwise the shadows appeared
far too aliased.
A new example, `pcss`, has been added. It demonstrates the
percentage-closer soft shadow technique with directional lights, point
lights, spot lights, non-temporal operation, and temporal operation. The
assets are my original work.
Both temporal and non-temporal shadows are rather noisy in the example,
and, as mentioned before, this is unavoidable without downsampling the
depth buffer, which we can't do yet. Note also that the shadows don't
look particularly great for point lights; the example simply isn't an
ideal scene for them. Nevertheless, I felt that the benefits of the
ability to do a side-by-side comparison of directional and point lights
outweighed the unsightliness of the point light shadows in that example,
so I kept the point light feature in.
Fixes#3631.
[*Percentage-closer soft shadows*]:
https://developer.download.nvidia.com/shaderlibrary/docs/shadow_PCSS.pdf
## Changelog
### Added
* Percentage-closer soft shadows (PCSS) are now supported, allowing
shadows to become blurrier as they stretch away from objects. To use
them, set the `soft_shadow_size` field in `DirectionalLight`,
`PointLight`, or `SpotLight`, as applicable.
* The near Z value for shadow maps is now customizable via the
`shadow_map_near_z` field in `DirectionalLight`, `PointLight`, and
`SpotLight`.
## Screenshots
PCSS off:
PCSS on:
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Torstein Grindvik <52322338+torsteingrindvik@users.noreply.github.com>
We want to use the clustering infrastructure for light probes and decals
as well, not just point lights. This patch builds on top of #13640 and
performs the rename.
To make this series easier to review, this patch makes no code changes.
Only identifiers and comments are modified.
## Migration Guide
* In the PBR shaders, `point_lights` is now known as
`clusterable_objects`, `PointLight` is now known as `ClusterableObject`,
and `cluster_light_index_lists` is now known as
`clusterable_object_index_lists`.
# Objective
- Fixes#10909
- Fixes#8492
## Solution
- Name all matrices `x_from_y`, for example `world_from_view`.
## Testing
- I've tested most of the 3D examples. The `lighting` example
particularly should hit a lot of the changes and appears to run fine.
---
## Changelog
- Renamed matrices across the engine to follow a `y_from_x` naming,
making the space conversion more obvious.
## Migration Guide
- `Frustum`'s `from_view_projection`, `from_view_projection_custom_far`
and `from_view_projection_no_far` were renamed to
`from_clip_from_world`, `from_clip_from_world_custom_far` and
`from_clip_from_world_no_far`.
- `ComputedCameraValues::projection_matrix` was renamed to
`clip_from_view`.
- `CameraProjection::get_projection_matrix` was renamed to
`get_clip_from_view` (this affects implementations on `Projection`,
`PerspectiveProjection` and `OrthographicProjection`).
- `ViewRangefinder3d::from_view_matrix` was renamed to
`from_world_from_view`.
- `PreviousViewData`'s members were renamed to `view_from_world` and
`clip_from_world`.
- `ExtractedView`'s `projection`, `transform` and `view_projection` were
renamed to `clip_from_view`, `world_from_view` and `clip_from_world`.
- `ViewUniform`'s `view_proj`, `unjittered_view_proj`,
`inverse_view_proj`, `view`, `inverse_view`, `projection` and
`inverse_projection` were renamed to `clip_from_world`,
`unjittered_clip_from_world`, `world_from_clip`, `world_from_view`,
`view_from_world`, `clip_from_view` and `view_from_clip`.
- `GpuDirectionalCascade::view_projection` was renamed to
`clip_from_world`.
- `MeshTransforms`' `transform` and `previous_transform` were renamed to
`world_from_local` and `previous_world_from_local`.
- `MeshUniform`'s `transform`, `previous_transform`,
`inverse_transpose_model_a` and `inverse_transpose_model_b` were renamed
to `world_from_local`, `previous_world_from_local`,
`local_from_world_transpose_a` and `local_from_world_transpose_b` (the
`Mesh` type in WGSL mirrors this, however `transform` and
`previous_transform` were named `model` and `previous_model`).
- `Mesh2dTransforms::transform` was renamed to `world_from_local`.
- `Mesh2dUniform`'s `transform`, `inverse_transpose_model_a` and
`inverse_transpose_model_b` were renamed to `world_from_local`,
`local_from_world_transpose_a` and `local_from_world_transpose_b` (the
`Mesh2d` type in WGSL mirrors this).
- In WGSL, in `bevy_pbr::mesh_functions`, `get_model_matrix` and
`get_previous_model_matrix` were renamed to `get_world_from_local` and
`get_previous_world_from_local`.
- In WGSL, `bevy_sprite::mesh2d_functions::get_model_matrix` was renamed
to `get_world_from_local`.
This commit implements a more physically-accurate, but slower, form of
fog than the `bevy_pbr::fog` module does. Notably, this *volumetric fog*
allows for light beams from directional lights to shine through,
creating what is known as *light shafts* or *god rays*.
To add volumetric fog to a scene, add `VolumetricFogSettings` to the
camera, and add `VolumetricLight` to directional lights that you wish to
be volumetric. `VolumetricFogSettings` has numerous settings that allow
you to define the accuracy of the simulation, as well as the look of the
fog. Currently, only interaction with directional lights that have
shadow maps is supported. Note that the overhead of the effect scales
directly with the number of directional lights in use, so apply
`VolumetricLight` sparingly for the best results.
The overall algorithm, which is implemented as a postprocessing effect,
is a combination of the techniques described in [Scratchapixel] and
[this blog post]. It uses raymarching in screen space, transformed into
shadow map space for sampling and combined with physically-based
modeling of absorption and scattering. Bevy employs the widely-used
[Henyey-Greenstein phase function] to model asymmetry; this essentially
allows light shafts to fade into and out of existence as the user views
them.
Volumetric rendering is a huge subject, and I deliberately kept the
scope of this commit small. Possible follow-ups include:
1. Raymarching at a lower resolution.
2. A post-processing blur (especially useful when combined with (1)).
3. Supporting point lights and spot lights.
4. Supporting lights with no shadow maps.
5. Supporting irradiance volumes and reflection probes.
6. Voxel components that reuse the volumetric fog code to create voxel
shapes.
7. *Horizon: Zero Dawn*-style clouds.
These are all useful, but out of scope of this patch for now, to keep
things tidy and easy to review.
A new example, `volumetric_fog`, has been added to demonstrate the
effect.
## Changelog
### Added
* A new component, `VolumetricFog`, is available, to allow for a more
physically-accurate, but more resource-intensive, form of fog.
* A new component, `VolumetricLight`, can be placed on directional
lights to make them interact with `VolumetricFog`. Notably, this allows
such lights to emit light shafts/god rays.
[Scratchapixel]:
https://www.scratchapixel.com/lessons/3d-basic-rendering/volume-rendering-for-developers/intro-volume-rendering.html
[this blog post]: https://www.alexandre-pestana.com/volumetric-lights/
[Henyey-Greenstein phase function]:
https://www.pbr-book.org/4ed/Volume_Scattering/Phase_Functions#TheHenyeyndashGreensteinPhaseFunction
# Objective
`bevy_pbr/utils.wgsl` shader file contains mathematical constants and
color conversion functions. Both of those should be accessible without
enabling `bevy_pbr` feature. For example, tonemapping can be done in non
pbr scenario, and it uses color conversion functions.
Fixes#13207
## Solution
* Move mathematical constants (such as PI, E) from
`bevy_pbr/src/render/utils.wgsl` into `bevy_render/src/maths.wgsl`
* Move color conversion functions from `bevy_pbr/src/render/utils.wgsl`
into new file `bevy_render/src/color_operations.wgsl`
## Testing
Ran multiple examples, checked they are working:
* tonemapping
* color_grading
* 3d_scene
* animated_material
* deferred_rendering
* 3d_shapes
* fog
* irradiance_volumes
* meshlet
* parallax_mapping
* pbr
* reflection_probes
* shadow_biases
* 2d_gizmos
* light_gizmos
---
## Changelog
* Moved mathematical constants (such as PI, E) from
`bevy_pbr/src/render/utils.wgsl` into `bevy_render/src/maths.wgsl`
* Moved color conversion functions from `bevy_pbr/src/render/utils.wgsl`
into new file `bevy_render/src/color_operations.wgsl`
## Migration Guide
In user's shader code replace usage of mathematical constants from
`bevy_pbr::utils` to the usage of the same constants from
`bevy_render::maths`.
This commit expands Bevy's existing tonemapping feature to a complete
set of filmic color grading tools, matching those of engines like Unity,
Unreal, and Godot. The following features are supported:
* White point adjustment. This is inspired by Unity's implementation of
the feature, but simplified and optimized. *Temperature* and *tint*
control the adjustments to the *x* and *y* chromaticity values of [CIE
1931]. Following Unity, the adjustments are made relative to the [D65
standard illuminant] in the [LMS color space].
* Hue rotation. This simply converts the RGB value to [HSV], alters the
hue, and converts back.
* Color correction. This allows the *gamma*, *gain*, and *lift* values
to be adjusted according to the standard [ASC CDL combined function].
* Separate color correction for shadows, midtones, and highlights.
Blender's source code was used as a reference for the implementation of
this. The midtone ranges can be adjusted by the user. To avoid abrupt
color changes, a small crossfade is used between the different sections
of the image, again following Blender's formulas.
A new example, `color_grading`, has been added, offering a GUI to change
all the color grading settings. It uses the same test scene as the
existing `tonemapping` example, which has been factored out into a
shared glTF scene.
[CIE 1931]: https://en.wikipedia.org/wiki/CIE_1931_color_space
[D65 standard illuminant]:
https://en.wikipedia.org/wiki/Standard_illuminant#Illuminant_series_D
[LMS color space]: https://en.wikipedia.org/wiki/LMS_color_space
[HSV]: https://en.wikipedia.org/wiki/HSL_and_HSV
[ASC CDL combined function]:
https://en.wikipedia.org/wiki/ASC_CDL#Combined_Function
## Changelog
### Added
* Many new filmic color grading options have been added to the
`ColorGrading` component.
## Migration Guide
* `ColorGrading::gamma` and `ColorGrading::pre_saturation` are now set
separately for the `shadows`, `midtones`, and `highlights` sections. You
can migrate code with the `ColorGrading::all_sections` and
`ColorGrading::all_sections_mut` functions, which access and/or update
all sections at once.
* `ColorGrading::post_saturation` and `ColorGrading::exposure` are now
fields of `ColorGrading::global`.
## Screenshots
I ported the two existing PCF techniques to the cubemap domain as best I
could. Generally, the technique is to create a 2D orthonormal basis
using Gram-Schmidt normalization, then apply the technique over that
basis. The results look fine, though the shadow bias often needs
adjusting.
For comparison, Unity uses a 4-tap pattern for PCF on point lights of
(1, 1, 1), (-1, -1, 1), (-1, 1, -1), (1, -1, -1). I tried this but
didn't like the look, so I went with the design above, which ports the
2D techniques to the 3D domain. There's surprisingly little material on
point light PCF.
I've gone through every example using point lights and verified that the
shadow maps look fine, adjusting biases as necessary.
Fixes#3628.
---
## Changelog
### Added
* Shadows from point lights now support percentage-closer filtering
(PCF), and as a result look less aliased.
### Changed
* `ShadowFilteringMethod::Castano13` and
`ShadowFilteringMethod::Jimenez14` have been renamed to
`ShadowFilteringMethod::Gaussian` and `ShadowFilteringMethod::Temporal`
respectively.
## Migration Guide
* `ShadowFilteringMethod::Castano13` and
`ShadowFilteringMethod::Jimenez14` have been renamed to
`ShadowFilteringMethod::Gaussian` and `ShadowFilteringMethod::Temporal`
respectively.
This PR closes#11978
# Objective
Fix rendering on iOS Simulators.
iOS Simulator doesn't support the capability CUBE_ARRAY_TEXTURES, since
0.13 this started to make iOS Simulator not render anything with the
following message being outputted:
```
2024-02-19T14:59:34.896266Z ERROR bevy_render::render_resource::pipeline_cache: failed to create shader module: Validation Error
Caused by:
In Device::create_shader_module
Shader validation error:
Type [40] '' is invalid
Capability Capabilities(CUBE_ARRAY_TEXTURES) is required
```
## Solution
- Split up NO_ARRAY_TEXTURES_SUPPORT into both NO_ARRAY_TEXTURES_SUPPORT
and NO_CUBE_ARRAY_TEXTURES_SUPPORT and correctly apply
NO_ARRAY_TEXTURES_SUPPORT for iOS Simulator using the cfg flag
introduced in #10178.
---
## Changelog
### Fixed
- Rendering on iOS Simulator due to missing CUBE_ARRAY_TEXTURES support.
---------
Co-authored-by: Sam Pettersson <sam.pettersson@geoguessr.com>
# Objective
- bump naga_oil to 0.10
- update shader imports to use rusty syntax
## Migration Guide
naga_oil 0.10 reworks the import mechanism to support more syntax to
make it more rusty, and test for item use before importing to determine
which imports are modules and which are items, which allows:
- use rust-style imports
```
#import bevy_pbr::{
pbr_functions::{alpha_discard as discard, apply_pbr_lighting},
mesh_bindings,
}
```
- import partial paths:
```
#import part::of::path
...
path::remainder::function();
```
which will call to `part::of::path::remainder::function`
- use fully qualified paths without importing:
```
// #import bevy_pbr::pbr_functions
bevy_pbr::pbr_functions::pbr()
```
- use imported items without qualifying
```
#import bevy_pbr::pbr_functions::pbr
// for backwards compatibility the old style is still supported:
// #import bevy_pbr::pbr_functions pbr
...
pbr()
```
- allows most imported items to end with `_` and numbers (naga_oil#30).
still doesn't allow struct members to end with `_` or numbers but it's
progress.
- the vast majority of existing shader code will work without changes,
but will emit "deprecated" warnings for old-style imports. these can be
suppressed with the `allow-deprecated` feature.
- partly breaks overrides (as far as i'm aware nobody uses these yet) -
now overrides will only be applied if the overriding module is added as
an additional import in the arguments to `Composer::make_naga_module` or
`Composer::add_composable_module`. this is necessary to support
determining whether imports are modules or items.
# Objective
- Improve antialiasing for non-point light shadow edges.
- Very partially addresses
https://github.com/bevyengine/bevy/issues/3628.
## Solution
- Implements "The Witness"'s shadow map sampling technique.
- Ported from @superdump's old branch, all credit to them :)
- Implements "Call of Duty: Advanced Warfare"'s stochastic shadow map
sampling technique when the velocity prepass is enabled, for use with
TAA.
- Uses interleaved gradient noise to generate a random angle, and then
averages 8 samples in a spiral pattern, rotated by the random angle.
- I also tried spatiotemporal blue noise, but it was far too noisy to be
filtered by TAA alone. In the future, we should try spatiotemporal blue
noise + a specialized shadow denoiser such as
https://gpuopen.com/fidelityfx-denoiser/#shadow. This approach would
also be useful for hybrid rasterized applications with raytraced
shadows.
- The COD presentation has an interesting temporal dithering of the
noise for use with temporal supersampling that we should revisit when we
get DLSS/FSR/other TSR.
---
## Changelog
* Added `ShadowFilteringMethod`. Improved directional light and
spotlight shadow edges to be less aliased.
## Migration Guide
* Shadows cast by directional lights or spotlights now have smoother
edges. To revert to the old behavior, add
`ShadowFilteringMethod::Hardware2x2` to your cameras.
---------
Co-authored-by: IceSentry <c.giguere42@gmail.com>
Co-authored-by: Daniel Chia <danstryder@gmail.com>
Co-authored-by: robtfm <50659922+robtfm@users.noreply.github.com>
Co-authored-by: Brandon Dyer <brandondyer64@gmail.com>
Co-authored-by: Edgar Geier <geieredgar@gmail.com>
Co-authored-by: Robert Swain <robert.swain@gmail.com>
Co-authored-by: Elabajaba <Elabajaba@users.noreply.github.com>
Co-authored-by: IceSentry <IceSentry@users.noreply.github.com>
# Objective
operate on naga IR directly to improve handling of shader modules.
- give codespan reporting into imported modules
- allow glsl to be used from wgsl and vice-versa
the ultimate objective is to make it possible to
- provide user hooks for core shader functions (to modify light
behaviour within the standard pbr pipeline, for example)
- make automatic binding slot allocation possible
but ... since this is already big, adds some value and (i think) is at
feature parity with the existing code, i wanted to push this now.
## Solution
i made a crate called naga_oil (https://github.com/robtfm/naga_oil -
unpublished for now, could be part of bevy) which manages modules by
- building each module independantly to naga IR
- creating "header" files for each supported language, which are used to
build dependent modules/shaders
- make final shaders by combining the shader IR with the IR for imported
modules
then integrated this into bevy, replacing some of the existing shader
processing stuff. also reworked examples to reflect this.
## Migration Guide
shaders that don't use `#import` directives should work without changes.
the most notable user-facing difference is that imported
functions/variables/etc need to be qualified at point of use, and
there's no "leakage" of visible stuff into your shader scope from the
imports of your imports, so if you used things imported by your imports,
you now need to import them directly and qualify them.
the current strategy of including/'spreading' `mesh_vertex_output`
directly into a struct doesn't work any more, so these need to be
modified as per the examples (e.g. color_material.wgsl, or many others).
mesh data is assumed to be in bindgroup 2 by default, if mesh data is
bound into bindgroup 1 instead then the shader def `MESH_BINDGROUP_1`
needs to be added to the pipeline shader_defs.
Fixes issue mentioned in PR #8285.
_Note: By mistake, this is currently dependent on #8285_
# Objective
Ensure consistency in the spelling of the documentation.
Exceptions:
`crates/bevy_mikktspace/src/generated.rs` - Has not been changed from
licence to license as it is part of a licensing agreement.
Maybe for further consistency,
https://github.com/bevyengine/bevy-website should also be given a look.
## Solution
### Changed the spelling of the current words (UK/CN/AU -> US) :
cancelled -> canceled (Breaking API changes in #8285)
behaviour -> behavior (Breaking API changes in #8285)
neighbour -> neighbor
grey -> gray
recognise -> recognize
centre -> center
metres -> meters
colour -> color
### ~~Update [`engine_style_guide.md`]~~ Moved to #8324
---
## Changelog
Changed UK spellings in documentation to US
## Migration Guide
Non-breaking changes*
\* If merged after #8285
# Objective
- Improve ergonomics / documentation of cascaded shadow maps
- Allow for the customization of the nearest shadowing distance.
- Fixes#7393
- Fixes#7362
## Solution
- Introduce `CascadeShadowConfigBuilder`
- Tweak various example cascade settings for better quality.
---
## Changelog
- Made examples look nicer under cascaded shadow maps.
- Introduce `CascadeShadowConfigBuilder` to help with creating `CascadeShadowConfig`
## Migration Guide
- Configure settings for cascaded shadow maps for directional lights using the newly introduced `CascadeShadowConfigBuilder`.
Co-authored-by: Robert Swain <robert.swain@gmail.com>
# Objective
I found several words in code and docs are incorrect. This should be fixed.
## Solution
- Fix several minor typos
Co-authored-by: Chris Ohk <utilforever@gmail.com>
Co-authored-by: Robert Swain <robert.swain@gmail.com>
# Objective
Implements cascaded shadow maps for directional lights, which produces better quality shadows without needing excessively large shadow maps.
Fixes#3629
Before
After
## Solution
Rather than rendering a single shadow map for directional light, the view frustum is divided into a series of cascades, each of which gets its own shadow map. The correct cascade is then sampled for shadow determination.
---
## Changelog
Directional lights now use cascaded shadow maps for improved shadow quality.
## Migration Guide
You no longer have to manually specify a `shadow_projection` for a directional light, and these settings should be removed. If customization of how cascaded shadow maps work is desired, modify the `CascadeShadowConfig` component instead.
# Objective
fix error with shadow shader's spotlight direction calculation when direction.y ~= 0
fixes#7152
## Solution
same as #6167: in shadows.wgsl, clamp 1-x^2-z^2 to >= 0 so that we can safely sqrt it
# Objective
- The #7064 PR had poor performance on an M1 Max in MacOS due to significant overuse of registers resulting in 'register spilling' where data that would normally be stored in registers on the GPU is instead stored in VRAM. The latency to read from/write to VRAM instead of registers incurs a significant performance penalty.
- Use of registers is a limiting factor in shader performance. Assignment of a struct from memory to a local variable can incur copies. Passing a variable that has struct type as an argument to a function can also incur copies. As such, these two cases can incur increased register usage and decreased performance.
## Solution
- Remove/avoid a number of assignments of light struct type data to local variables.
- Remove/avoid a number of passing light struct type variables/data as value arguments to shader functions.
# Objective
add spotlight support
## Solution / Changelog
- add spotlight angles (inner, outer) to ``PointLight`` struct. emitted light is linearly attenuated from 100% to 0% as angle tends from inner to outer. Direction is taken from the existing transform rotation.
- add spotlight direction (vec3) and angles (f32,f32) to ``GpuPointLight`` struct (60 bytes -> 80 bytes) in ``pbr/render/lights.rs`` and ``mesh_view_bind_group.wgsl``
- reduce no-buffer-support max point light count to 204 due to above
- use spotlight data to attenuate light in ``pbr.wgsl``
- do additional cluster culling on spotlights to minimise cost in ``assign_lights_to_clusters``
- changed one of the lights in the lighting demo to a spotlight
- also added a ``spotlight`` demo - probably not justified but so reviewers can see it more easily
## notes
increasing the size of the GpuPointLight struct on my machine reduces the FPS of ``many_lights -- sphere`` from ~150fps to 140fps.
i thought this was a reasonable tradeoff, and felt better than handling spotlights separately which is possible but would mean introducing a new bind group, refactoring light-assignment code and adding new spotlight-specific code in pbr.wgsl. the FPS impact for smaller numbers of lights should be very small.
the cluster culling strategy reintroduces the cluster aabb code which was recently removed... sorry. the aabb is used to get a cluster bounding sphere, which can then be tested fairly efficiently using the strategy described at the end of https://bartwronski.com/2017/04/13/cull-that-cone/. this works well with roughly cubic clusters (where the cluster z size is close to the same as x/y size), less well for other cases like single Z slice / tiled forward rendering. In the worst case we will end up just keeping the culling of the equivalent point light.
Co-authored-by: François <mockersf@gmail.com>
# Objective
- Builds on top of #4901
- Separate out PBR lighting, shadows, clustered forward, and utils from `pbr.wgsl` as part of making the PBR code more reusable and extensible.
- See #3969 for details.
## Solution
- Add `bevy_pbr::utils`, `bevy_pbr::clustered_forward`, `bevy_pbr::lighting`, `bevy_pbr::shadows` shader imports exposing many shader functions for external use
- Split `PI`, `saturate()`, `hsv2rgb()`, and `random1D()` into `bevy_pbr::utils`
- Split clustered-forward-specific functions into `bevy_pbr::clustered_forward`, including moving the debug visualization code into a `cluster_debug_visualization()` function in that import
- Split PBR lighting functions into `bevy_pbr::lighting`
- Split shadow functions into `bevy_pbr::shadows`
---
## Changelog
- Added: `bevy_pbr::utils`, `bevy_pbr::clustered_forward`, `bevy_pbr::lighting`, `bevy_pbr::shadows` shader imports exposing many shader functions for external use
- Split `PI`, `saturate()`, `hsv2rgb()`, and `random1D()` into `bevy_pbr::utils`
- Split clustered-forward-specific functions into `bevy_pbr::clustered_forward`, including moving the debug visualization code into a `cluster_debug_visualization()` function in that import
- Split PBR lighting functions into `bevy_pbr::lighting`
- Split shadow functions into `bevy_pbr::shadows`
