 1fcf6a444f
			
		
	
	
		1fcf6a444f
		
			
		
	
	
	
	
		
			
			# Objective
- The emissive color gets multiplied by the camera exposure value. But
this cancels out almost any emissive effect.
- Fixes #13133
- Closes PR #13337 
## Solution
- Add emissive_exposure_weight to the StandardMaterial
- In the shader this value is stored in the alpha channel of the
emissive color.
- This value defines how much the exposure influences the emissive
color.
- It's equal to Google's Filament:
https://google.github.io/filament/Materials.html#emissive
4f021583f1/shaders/src/shading_lit.fs (L287)
## Testing
- The result of
[EmissiveStrengthTest](https://github.com/KhronosGroup/glTF-Sample-Models/tree/main/2.0/EmissiveStrengthTest)
with the default value of 0.0:
without bloom:

with bloom:

		
	
			
		
			
				
	
	
		
			66 lines
		
	
	
		
			2.0 KiB
		
	
	
	
		
			Rust
		
	
	
	
	
	
			
		
		
	
	
			66 lines
		
	
	
		
			2.0 KiB
		
	
	
	
		
			Rust
		
	
	
	
	
	
| //! Rendering a scene with baked lightmaps.
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| 
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| use bevy::pbr::Lightmap;
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| use bevy::prelude::*;
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| 
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| fn main() {
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|     App::new()
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|         .add_plugins(DefaultPlugins)
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|         .insert_resource(AmbientLight::NONE)
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|         .add_systems(Startup, setup)
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|         .add_systems(Update, add_lightmaps_to_meshes)
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|         .run();
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| }
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| 
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| fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
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|     commands.spawn(SceneBundle {
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|         scene: asset_server.load("models/CornellBox/CornellBox.glb#Scene0"),
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|         ..default()
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|     });
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| 
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|     commands.spawn(Camera3dBundle {
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|         transform: Transform::from_xyz(-278.0, 273.0, 800.0),
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|         ..default()
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|     });
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| }
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| 
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| fn add_lightmaps_to_meshes(
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|     mut commands: Commands,
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|     asset_server: Res<AssetServer>,
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|     mut materials: ResMut<Assets<StandardMaterial>>,
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|     meshes: Query<
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|         (Entity, &Name, &Handle<StandardMaterial>),
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|         (With<Handle<Mesh>>, Without<Lightmap>),
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|     >,
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| ) {
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|     let exposure = 250.0;
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|     for (entity, name, material) in meshes.iter() {
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|         if &**name == "large_box" {
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|             materials.get_mut(material).unwrap().lightmap_exposure = exposure;
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|             commands.entity(entity).insert(Lightmap {
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|                 image: asset_server.load("lightmaps/CornellBox-Large.zstd.ktx2"),
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|                 ..default()
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|             });
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|             continue;
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|         }
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| 
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|         if &**name == "small_box" {
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|             materials.get_mut(material).unwrap().lightmap_exposure = exposure;
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|             commands.entity(entity).insert(Lightmap {
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|                 image: asset_server.load("lightmaps/CornellBox-Small.zstd.ktx2"),
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|                 ..default()
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|             });
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|             continue;
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|         }
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| 
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|         if name.starts_with("cornell_box") {
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|             materials.get_mut(material).unwrap().lightmap_exposure = exposure;
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|             commands.entity(entity).insert(Lightmap {
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|                 image: asset_server.load("lightmaps/CornellBox-Box.zstd.ktx2"),
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|                 ..default()
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|             });
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|             continue;
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|         }
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|     }
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| }
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