# Objective
Add web support to atmosphere by gating dual source blending and using a
macro to determine the target platform.
The main objective of this PR is to ensure that users of Bevy's
atmosphere feature can also run it in a web-based context where WebGPU
support is enabled.
## Solution
- Make use of the `#[cfg(not(target_arch = "wasm32"))]` macro to gate
the dual source blending, as this is not (yet) supported in web
browsers.
- Rename the function `sample_sun_illuminance` to `sample_sun_radiance`
and move calls out of conditionals to ensure the shader compiles and
runs in both native and web-based contexts.
- Moved the multiplication of the transmittance out when calculating the
sun color, because calling the `sample_sun_illuminance` function was
causing issues in web. Overall this results in cleaner code and more
readable.
## Testing
- Tested by building a wasm target and loading it in a web page with
Vite dev server using `mate-h/bevy-webgpu` repo template.
- Tested the native build with `cargo run --example atmosphere` to
ensure it still works with dual source blending.
---
## Showcase
Screenshots show the atmosphere example running in two different
contexts:
<img width="1281" alt="atmosphere-web-showcase"
src="https://github.com/user-attachments/assets/40b1ee91-89ae-41a6-8189-89630d1ca1a6"
/>
---------
Co-authored-by: JMS55 <47158642+JMS55@users.noreply.github.com>
# Objective
Since previously we only had the alpha channel available, we stored the
mean of the transmittance in the aerial view lut, resulting in a grayer
fog than should be expected.
## Solution
- Calculate transmittance to scene in `render_sky` with two samples from
the transmittance lut
- use dual-source blending to effectively have per-component alpha
blending
Implement procedural atmospheric scattering from [Sebastien Hillaire's
2020 paper](https://sebh.github.io/publications/egsr2020.pdf). This
approach should scale well even down to mobile hardware, and is
physically accurate.
## Co-author: @mate-h
He helped massively with getting this over the finish line, ensuring
everything was physically correct, correcting several places where I had
misunderstood or misapplied the paper, and improving the performance in
several places as well. Thanks!
## Credits
@aevyrie: helped find numerous bugs and improve the example to best show
off this feature :)
Built off of @mtsr's original branch, which handled the transmittance
lut (arguably the most important part)
## Showcase:
## For followup
- Integrate with pcwalton's volumetrics code
- refactor/reorganize for better integration with other effects
- have atmosphere transmittance affect directional lights
- add support for generating skybox/environment map
---------
Co-authored-by: Emerson Coskey <56370779+EmersonCoskey@users.noreply.github.com>
Co-authored-by: atlv <email@atlasdostal.com>
Co-authored-by: JMS55 <47158642+JMS55@users.noreply.github.com>
Co-authored-by: Emerson Coskey <coskey@emerlabs.net>
Co-authored-by: Máté Homolya <mate.homolya@gmail.com>
