As a prerequisite for decals and clustering of light probes, we want
clustering to operate on objects other than lights. (Currently, it only
operates on point and spot lights.) This necessitates a large
refactoring, so I'm splitting it up into small steps.
The first such step is to separate clustering from lighting by moving
clustering-related types and functions out of lighting and into their
own module subtree within the `bevy_pbr` crate. (Ultimately, we may want
to move it to `bevy_render`, but that requires more work and can be a
followup.)
No code changes have been made other than adjusting import lists and
moving code. This is to make this code easy to review. Ultimately, I
want to rename "light" to "clusterable object" in most cases, but doing
that at the same time as moving the code would make reviewing harder. So
instead I'm moving the code first and will follow this up with renaming.
## Migration Guide
* Clustering-related types and functions (e.g.
`assign_lights_to_clusters`) have moved under `bevy_pbr::cluster`, in
preparation for the ability to cluster objects other than lights.
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
Remove the limit of `RenderLayer` by using a growable mask using
`SmallVec`.
Changes adopted from @UkoeHB's initial PR here
https://github.com/bevyengine/bevy/pull/12502 that contained additional
changes related to propagating render layers.
Changes
## Solution
The main thing needed to unblock this is removing `RenderLayers` from
our shader code. This primarily affects `DirectionalLight`. We are now
computing a `skip` field on the CPU that is then used to skip the light
in the shader.
## Testing
Checked a variety of examples and did a quick benchmark on `many_cubes`.
There were some existing problems identified during the development of
the original pr (see:
https://discord.com/channels/691052431525675048/1220477928605749340/1221190112939872347).
This PR shouldn't change any existing behavior besides removing the
layer limit (sans the comment in migration about `all` layers no longer
being possible).
---
## Changelog
Removed the limit on `RenderLayers` by using a growable bitset that only
allocates when layers greater than 64 are used.
## Migration Guide
- `RenderLayers::all()` no longer exists. Entities expecting to be
visible on all layers, e.g. lights, should compute the active layers
that are in use.
---------
Co-authored-by: robtfm <50659922+robtfm@users.noreply.github.com>
Implement visibility ranges, also known as hierarchical levels of detail
(HLODs).
This commit introduces a new component, `VisibilityRange`, which allows
developers to specify camera distances in which meshes are to be shown
and hidden. Hiding meshes happens early in the rendering pipeline, so
this feature can be used for level of detail optimization. Additionally,
this feature is properly evaluated per-view, so different views can show
different levels of detail.
This feature differs from proper mesh LODs, which can be implemented
later. Engines generally implement true mesh LODs later in the pipeline;
they're typically more efficient than HLODs with GPU-driven rendering.
However, mesh LODs are more limited than HLODs, because they require the
lower levels of detail to be meshes with the same vertex layout and
shader (and perhaps the same material) as the original mesh. Games often
want to use objects other than meshes to replace distant models, such as
*octahedral imposters* or *billboard imposters*.
The reason why the feature is called *hierarchical level of detail* is
that HLODs can replace multiple meshes with a single mesh when the
camera is far away. This can be useful for reducing drawcall count. Note
that `VisibilityRange` doesn't automatically propagate down to children;
it must be placed on every mesh.
Crossfading between different levels of detail is supported, using the
standard 4x4 ordered dithering pattern from [1]. The shader code to
compute the dithering patterns should be well-optimized. The dithering
code is only active when visibility ranges are in use for the mesh in
question, so that we don't lose early Z.
Cascaded shadow maps show the HLOD level of the view they're associated
with. Point light and spot light shadow maps, which have no CSMs,
display all HLOD levels that are visible in any view. To support this
efficiently and avoid doing visibility checks multiple times, we
precalculate all visible HLOD levels for each entity with a
`VisibilityRange` during the `check_visibility_range` system.
A new example, `visibility_range`, has been added to the tree, as well
as a new low-poly version of the flight helmet model to go with it. It
demonstrates use of the visibility range feature to provide levels of
detail.
[1]: https://en.wikipedia.org/wiki/Ordered_dithering#Threshold_map
[^1]: Unreal doesn't have a feature that exactly corresponds to
visibility ranges, but Unreal's HLOD system serves roughly the same
purpose.
## Changelog
### Added
* A new `VisibilityRange` component is available to conditionally enable
entity visibility at camera distances, with optional crossfade support.
This can be used to implement different levels of detail (LODs).
## Screenshots
High-poly model:
Low-poly model up close:
Crossfading between the two:
---------
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
This commit splits `VisibleEntities::entities` into four separate lists:
one for lights, one for 2D meshes, one for 3D meshes, and one for UI
elements. This allows `queue_material_meshes` and similar methods to
avoid examining entities that are obviously irrelevant. In particular,
this separation helps scenes with many skinned meshes, as the individual
bones are considered visible entities but have no rendered appearance.
Internally, `VisibleEntities::entities` is a `HashMap` from the `TypeId`
representing a `QueryFilter` to the appropriate `Entity` list. I had to
do this because `VisibleEntities` is located within an upstream crate
from the crates that provide lights (`bevy_pbr`) and 2D meshes
(`bevy_sprite`). As an added benefit, this setup allows apps to provide
their own types of renderable components, by simply adding a specialized
`check_visibility` to the schedule.
This provides a 16.23% end-to-end speedup on `many_foxes` with 10,000
foxes (24.06 ms/frame to 20.70 ms/frame).
## Migration guide
* `check_visibility` and `VisibleEntities` now store the four types of
renderable entities--2D meshes, 3D meshes, lights, and UI
elements--separately. If your custom rendering code examines
`VisibleEntities`, it will now need to specify which type of entity it's
interested in using the `WithMesh2d`, `WithMesh`, `WithLight`, and
`WithNode` types respectively. If your app introduces a new type of
renderable entity, you'll need to add an explicit call to
`check_visibility` to the schedule to accommodate your new component or
components.
## Analysis
`many_foxes`, 10,000 foxes: `main`:
`many_foxes`, 10,000 foxes, this branch:
`queue_material_meshes` (yellow = this branch, red = `main`):
`queue_shadows` (yellow = this branch, red = `main`):
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.
# Objective
Follow up from PR #12369 to extract lighting structs from light/mod.rs
into their own file.
Part of the Purdue Refactoring Team's goals issue #12349
## Solution
- Moved PointLight from light/mod.rs to light/point_light.rs
- Moved SpotLight from light/mod.rs to light/spot_light.rs
- Moved DirectionalLight from light/mod.rs to light/directional_light.rs
# Objective
Beginning of refactoring of light.rs in bevy_pbr, as per issue #12349
Create and move light.rs to its own directory, and extract AmbientLight
struct.
## Solution
- moved light.rs to light/mod.rs
- extracted AmbientLight struct to light/ambient_light.rs
