# Objective
- @mockersf identified a performance regression of about 25% longer frame times introduced by #7784 in a complex scene with the Amazon Lumberyard bistro scene with both exterior and interior variants and a number of point lights with shadow mapping enabled
- The additional time seemed to be spent in the `ShadowPassNode`
- `ShadowPassNode` encodes the draw commands for the shadow phase. Roughly the same numbers of entities were having draw commands encoded, so something about the way they were being encoded had changed.
- One thing that definitely changed was that the pipeline used will be different depending on the alpha mode, and the scene has lots entities with opaque and blend materials. This suggested that maybe the pipeline was changing a lot so I tried a quick hack to see if it was the problem.
## Solution
- Sort the shadow phase items by their pipeline id
- This groups phase items by their pipeline id, which significantly reduces pipeline rebinding required to the point that the performance regression was gone.
# Objective
- Currently, https://github.com/vleue/bevy_bistro_playground crashes when enabling shadows, because this allocates a new buffer for the view uniforms, but the `TonemappingNode` uses a cached bind group that doesn't reference the new uniform buffer.
## Solution
- Check if the buffer id of the view uniforms buffer has changed and create a new bind group if it did.
# Objective
Fixes#7757
New function `Color::as_lcha` was added and `Color::as_lch_f32` changed name to `Color::as_lcha_f32`.
----
As a side note I did it as in every other Color function, that is I created very simillar code in `as_lcha` as was in `as_lcha_f32`. However it is totally possible to avoid this code duplication in LCHA and other color variants by doing something like :
```
pub fn as_lcha(self: &Color) -> Color {
let (lightness, chroma, hue, alpha) = self.as_lcha_f32();
return Color::Lcha { lightness, chroma, hue, alpha };
}
```
This is maybe slightly less efficient but it avoids copy-pasting this huge match expression which is error prone. Anyways since it is my first commit here I wanted to be consistent with the rest of code but can refactor all variants in separate PR if somebody thinks it is good idea.
# Objective
revert combining pipelines for AlphaMode::Blend and AlphaMode::Premultiplied & Add
the recent blend state pr changed `AlphaMode::Blend` to use a blend state of `Blend::PREMULTIPLIED_ALPHA_BLENDING`, and recovered the original behaviour by multiplying colour by alpha in the standard material's fragment shader.
this had some advantages (specifically it means more material instances can be batched together in future), but this also means that custom materials that specify `AlphaMode::Blend` now get a premultiplied blend state, so they must also multiply colour by alpha.
## Solution
revert that combination to preserve 0.9 behaviour for custom materials with AlphaMode::Blend.
This produces more accurate results for the `EmissiveStrengthTest` glTF test case.
(Requires manually setting the emission, for now)
Before: <img width="1392" alt="Screenshot 2023-03-04 at 18 21 25" src="https://user-images.githubusercontent.com/418473/222929455-c7363d52-7133-4d4e-9d6a-562098f6bbe8.png">
After: <img width="1392" alt="Screenshot 2023-03-04 at 18 20 57" src="https://user-images.githubusercontent.com/418473/222929454-3ea20ecb-0773-4aad-978c-3832353b6871.png">
Tagging @JMS55 as a co-author, since this fix is based on their experiments with emission.
# Objective
- Have more accurate results for the `EmissiveStrengthTest` glTF test case.
## Solution
- Make sure we send the emissive color as linear instead of sRGB.
---
## Changelog
- Emission strength is now correctly interpreted by the `StandardMaterial` as linear instead of sRGB.
## Migration Guide
- If you have previously manually specified emissive values with `Color::rgb()` and would like to retain the old visual results, you must now use `Color::rgb_linear()` instead;
- If you have previously manually specified emissive values with `Color::rgb_linear()` and would like to retain the old visual results, you'll need to apply a one-time gamma calculation to your channels manually to get the _actual_ linear RGB value:
- For channel values greater than `0.0031308`, use `(1.055 * value.powf(1.0 / 2.4)) - 0.055`;
- For channel values lower than or equal to `0.0031308`, use `value * 12.92`;
- Otherwise, the results should now be more consistent with other tools/engines.
