Improve bloom add option to use faster but lower quality bloom

Author: beicause

crates/bevy_post_process/src/bloom/bloom.wgsl

@@ -49,6 +49,43 @@ fn karis_average(color: vec3<f32>) -> f32 {
     return 1.0 / (1.0 + luma);
 }
 
+// https://www.shadertoy.com/view/mdsyDf
+#ifdef FAST_BLUR
+fn bloom_down_kernel4(uv: vec2<f32>) -> vec3<f32> {
+	let ps = uniforms.scale / vec2<f32>(textureDimensions(input_texture));
+	let o = 0.5 + 1.0 / 4.0;
+
+	let a = textureSample(input_texture, s, uv + vec2<f32>(-1.0, -1.0) * o * ps).rgb * 0.25;
+	let b = textureSample(input_texture, s, uv + vec2<f32>(1.0, -1.0) * o * ps).rgb * 0.25;
+	let c = textureSample(input_texture, s, uv + vec2<f32>(-1.0, 1.0) * o * ps).rgb * 0.25;
+	let d = textureSample(input_texture, s, uv + vec2<f32>(1.0, 1.0) * o * ps).rgb * 0.25;
+
+#ifdef FIRST_DOWNSAMPLE
+	return (a + b + c + d) * karis_average(a + b + c + d);
+#else
+	return a + b + c + d;
+#endif
+}
+
+fn bloom_up_kernel4(uv: vec2<f32>) -> vec3<f32> {
+	// Modified version of BloomUpKernel4B https://www.shadertoy.com/view/mdsyDf. I couldn't get a good result with the original version.
+	let ps = uniforms.scale / vec2<f32>(textureDimensions(input_texture));
+    let w = vec4<f32>(0.211029, 0.288971, 0.288971, 0.211029);
+    // Add a small offset for better radial symmetry.
+    let l00 = vec2<f32>(0.347209, 0.526425) + 0.1;
+    let l10 = vec2<f32>(0.109840, 0.334045) + 0.1;
+    let l01 = vec2<f32>(0.334045, 0.109840) + 0.1;
+    let l11 = vec2<f32>(0.526425, 0.347209) + 0.1;
+
+	let a = textureSample(input_texture, s, uv + (vec2<f32>( -0.5, -1.5) + l00) * ps).rgb * w.x;
+	let b = textureSample(input_texture, s, uv + (vec2<f32>(0.5, -0.5) + l10) * ps).rgb * w.y;
+	let c = textureSample(input_texture, s, uv + (vec2<f32>( -0.5, 0.5) + l01) * ps).rgb * w.z;
+	let d = textureSample(input_texture, s, uv + (vec2<f32>( -1.5,-0.5) + l11) * ps).rgb * w.w;
+
+    return a + b + c + d;
+}
+#endif
+
 // [COD] slide 153
 fn sample_input_13_tap(uv: vec2<f32>) -> vec3<f32> {
 #ifdef UNIFORM_SCALE
@@ -161,7 +198,11 @@ fn sample_input_3x3_tent(uv: vec2<f32>) -> vec3<f32> {
 @fragment
 fn downsample_first(@location(0) output_uv: vec2<f32>) -> @location(0) vec4<f32> {
     let sample_uv = uniforms.viewport.xy + output_uv * uniforms.viewport.zw;
+#ifdef FAST_BLUR
+	var sample = bloom_down_kernel4(sample_uv);
+#else
     var sample = sample_input_13_tap(sample_uv);
+#endif
     // Lower bound of 0.0001 is to avoid propagating multiplying by 0.0 through the
     // downscaling and upscaling which would result in black boxes.
     // The upper bound is to prevent NaNs.
@@ -178,10 +219,18 @@ fn downsample_first(@location(0) output_uv: vec2<f32>) -> @location(0) vec4<f32>
 
 @fragment
 fn downsample(@location(0) uv: vec2<f32>) -> @location(0) vec4<f32> {
+#ifdef FAST_BLUR
+	return vec4<f32>(bloom_down_kernel4(uv), 1.0);
+#else
     return vec4<f32>(sample_input_13_tap(uv), 1.0);
+#endif
 }
 
 @fragment
 fn upsample(@location(0) uv: vec2<f32>) -> @location(0) vec4<f32> {
+#ifdef FAST_BLUR
+	return vec4<f32>(bloom_up_kernel4(uv), 1.0);
+#else
     return vec4<f32>(sample_input_3x3_tent(uv), 1.0);
+#endif
 }

crates/bevy_post_process/src/bloom/downsampling_pipeline.rs

@@ -40,6 +40,7 @@ pub struct BloomDownsamplingPipelineKeys {
     prefilter: bool,
     first_downsample: bool,
     uniform_scale: bool,
+    high_quality: bool,
 }
 
 /// The uniform struct extracted from [`Bloom`] attached to a Camera.
@@ -79,8 +80,9 @@ pub fn init_bloom_downsampling_pipeline(
     let sampler = render_device.create_sampler(&SamplerDescriptor {
         min_filter: FilterMode::Linear,
         mag_filter: FilterMode::Linear,
-        address_mode_u: AddressMode::ClampToEdge,
-        address_mode_v: AddressMode::ClampToEdge,
+        address_mode_u: AddressMode::ClampToBorder,
+        address_mode_v: AddressMode::ClampToBorder,
+        border_color: Some(SamplerBorderColor::TransparentBlack),
         ..Default::default()
     });
 
@@ -110,6 +112,10 @@ impl SpecializedRenderPipeline for BloomDownsamplingPipeline {
             shader_defs.push("FIRST_DOWNSAMPLE".into());
         }
 
+        if !key.high_quality {
+            shader_defs.push("FAST_BLUR".into());
+        }
+
         if key.prefilter {
             shader_defs.push("USE_THRESHOLD".into());
         }
@@ -161,6 +167,7 @@ pub fn prepare_downsampling_pipeline(
                 prefilter,
                 first_downsample: false,
                 uniform_scale: bloom.scale == Vec2::ONE,
+                high_quality: bloom.high_quality,
             },
         );
 
@@ -171,6 +178,7 @@ pub fn prepare_downsampling_pipeline(
                 prefilter,
                 first_downsample: true,
                 uniform_scale: bloom.scale == Vec2::ONE,
+                high_quality: bloom.high_quality,
             },
         );
 

crates/bevy_post_process/src/bloom/mod.rs

@@ -181,7 +181,7 @@ impl ViewNode for BloomNode {
                     &BindGroupEntries::sequential((
                         // Read from main texture directly
                         view_texture,
-                        &bind_groups.sampler,
+                        &downsampling_pipeline_res.sampler,
                         uniforms.clone(),
                     )),
                 );
@@ -361,16 +361,20 @@ fn prepare_bloom_textures(
     for (entity, camera, bloom) in &views {
         if let Some(viewport) = camera.physical_viewport_size {
             // How many times we can halve the resolution minus one so we don't go unnecessarily low
-            let mip_count = bloom.max_mip_dimension.ilog2().max(2) - 1;
-            let mip_height_ratio = if viewport.y != 0 {
-                bloom.max_mip_dimension as f32 / viewport.y as f32
+            let mip_count = bloom
+                .max_mip_dimension
+                .ilog2()
+                .clamp(2, bloom.max_mip_count)
+                - 1;
+            let mip_dim_ratio = if viewport.y != 0 && viewport.x != 0 {
+                (bloom.max_mip_dimension as f32 / viewport.as_vec2()).max_element()
             } else {
                 0.
             };
 
             let texture_descriptor = TextureDescriptor {
                 label: Some("bloom_texture"),
-                size: (viewport.as_vec2() * mip_height_ratio)
+                size: (viewport.as_vec2() * mip_dim_ratio)
                     .round()
                     .as_uvec2()
                     .max(UVec2::ONE)
@@ -419,7 +423,6 @@ struct BloomBindGroups {
     cache_key: (TextureId, BufferId),
     downsampling_bind_groups: Box<[BindGroup]>,
     upsampling_bind_groups: Box<[BindGroup]>,
-    sampler: Sampler,
 }
 
 fn prepare_bloom_bind_groups(
@@ -430,8 +433,6 @@ fn prepare_bloom_bind_groups(
     views: Query<(Entity, &BloomTexture, Option<&BloomBindGroups>)>,
     uniforms: Res<ComponentUniforms<BloomUniforms>>,
 ) {
-    let sampler = &downsampling_pipeline.sampler;
-
     for (entity, bloom_texture, bloom_bind_groups) in &views {
         if let Some(b) = bloom_bind_groups
             && b.cache_key
@@ -452,7 +453,7 @@ fn prepare_bloom_bind_groups(
                 &downsampling_pipeline.bind_group_layout,
                 &BindGroupEntries::sequential((
                     &bloom_texture.view(mip - 1),
-                    sampler,
+                    &downsampling_pipeline.sampler,
                     uniforms.binding().unwrap(),
                 )),
             ));
@@ -465,7 +466,7 @@ fn prepare_bloom_bind_groups(
                 &upsampling_pipeline.bind_group_layout,
                 &BindGroupEntries::sequential((
                     &bloom_texture.view(mip),
-                    sampler,
+                    &upsampling_pipeline.sampler,
                     uniforms.binding().unwrap(),
                 )),
             ));
@@ -478,7 +479,6 @@ fn prepare_bloom_bind_groups(
             ),
             downsampling_bind_groups: downsampling_bind_groups.into_boxed_slice(),
             upsampling_bind_groups: upsampling_bind_groups.into_boxed_slice(),
-            sampler: sampler.clone(),
         });
     }
 }

crates/bevy_post_process/src/bloom/settings.rs

@@ -116,13 +116,21 @@ pub struct Bloom {
     pub composite_mode: BloomCompositeMode,
 
     /// Maximum size of each dimension for the largest mipchain texture used in downscaling/upscaling.
-    /// Only tweak if you are seeing visual artifacts.
+    /// Lower values can improve performance but result in more aliasing.
     pub max_mip_dimension: u32,
 
+    /// Maximum number of mipmaps to use in downscaling/upscaling (default: [`u32::MAX`]).
+    /// Lower values can improve performance but lose some low frequency contributions.
+    pub max_mip_count: u32,
+
     /// Amount to stretch the bloom on each axis. Artistic control, can be used to emulate
     /// anamorphic blur by using a large x-value. For large values, you may need to increase
     /// [`Bloom::max_mip_dimension`] to reduce sampling artifacts.
     pub scale: Vec2,
+
+    // Whether to use a high quality bloom implementation (default: true).
+    // If false, bloom will use an implementation that significantly reduces the number of texture samples and improves performance, but at the cost of lower quality.
+    pub high_quality: bool,
 }
 
 impl Bloom {
@@ -143,6 +151,8 @@ impl Bloom {
         composite_mode: BloomCompositeMode::EnergyConserving,
         max_mip_dimension: Self::DEFAULT_MAX_MIP_DIMENSION,
         scale: Vec2::ONE,
+        high_quality: true,
+        max_mip_count: u32::MAX,
     };
 
     /// Emulates the look of stylized anamorphic bloom, stretched horizontally.
@@ -166,6 +176,8 @@ impl Bloom {
         composite_mode: BloomCompositeMode::Additive,
         max_mip_dimension: Self::DEFAULT_MAX_MIP_DIMENSION,
         scale: Vec2::ONE,
+        high_quality: true,
+        max_mip_count: u32::MAX,
     };
 
     /// A preset that applies a very strong bloom, and blurs the whole screen.
@@ -181,6 +193,8 @@ impl Bloom {
         composite_mode: BloomCompositeMode::EnergyConserving,
         max_mip_dimension: Self::DEFAULT_MAX_MIP_DIMENSION,
         scale: Vec2::ONE,
+        high_quality: true,
+        max_mip_count: u32::MAX,
     };
 }
 

crates/bevy_post_process/src/bloom/upsampling_pipeline.rs

@@ -29,6 +29,7 @@ pub struct UpsamplingPipelineIds {
 #[derive(Resource)]
 pub struct BloomUpsamplingPipeline {
     pub bind_group_layout: BindGroupLayout,
+    pub sampler: Sampler,
     /// The asset handle for the fullscreen vertex shader.
     pub fullscreen_shader: FullscreenShader,
     /// The fragment shader asset handle.
@@ -39,6 +40,7 @@ pub struct BloomUpsamplingPipeline {
 pub struct BloomUpsamplingPipelineKeys {
     composite_mode: BloomCompositeMode,
     final_pipeline: bool,
+    high_quality: bool,
 }
 
 pub fn init_bloom_upscaling_pipeline(
@@ -62,8 +64,18 @@ pub fn init_bloom_upscaling_pipeline(
         ),
     );
 
+    // Sampler
+    let sampler = render_device.create_sampler(&SamplerDescriptor {
+        min_filter: FilterMode::Linear,
+        mag_filter: FilterMode::Linear,
+        address_mode_u: AddressMode::ClampToEdge,
+        address_mode_v: AddressMode::ClampToEdge,
+        ..Default::default()
+    });
+
     commands.insert_resource(BloomUpsamplingPipeline {
         bind_group_layout,
+        sampler,
         fullscreen_shader: fullscreen_shader.clone(),
         fragment_shader: load_embedded_asset!(asset_server.as_ref(), "bloom.wgsl"),
     });
@@ -79,6 +91,11 @@ impl SpecializedRenderPipeline for BloomUpsamplingPipeline {
             BLOOM_TEXTURE_FORMAT
         };
 
+        let mut shader_defs = vec![];
+        if !key.high_quality {
+            shader_defs.push("FAST_BLUR".into());
+        }
+
         let color_blend = match key.composite_mode {
             BloomCompositeMode::EnergyConserving => {
                 // At the time of developing this we decided to blend our
@@ -117,6 +134,7 @@ impl SpecializedRenderPipeline for BloomUpsamplingPipeline {
             vertex: self.fullscreen_shader.to_vertex_state(),
             fragment: Some(FragmentState {
                 shader: self.fragment_shader.clone(),
+                shader_defs,
                 entry_point: Some("upsample".into()),
                 targets: vec![Some(ColorTargetState {
                     format: texture_format,
@@ -130,7 +148,6 @@ impl SpecializedRenderPipeline for BloomUpsamplingPipeline {
                     }),
                     write_mask: ColorWrites::ALL,
                 })],
-                ..default()
             }),
             ..default()
         }
@@ -151,6 +168,7 @@ pub fn prepare_upsampling_pipeline(
             BloomUpsamplingPipelineKeys {
                 composite_mode: bloom.composite_mode,
                 final_pipeline: false,
+                high_quality: bloom.high_quality,
             },
         );
 
@@ -160,6 +178,7 @@ pub fn prepare_upsampling_pipeline(
             BloomUpsamplingPipelineKeys {
                 composite_mode: bloom.composite_mode,
                 final_pipeline: true,
+                high_quality: bloom.high_quality,
             },
         );
 

crates/bevy_render/src/render_resource/mod.rs

@@ -55,8 +55,8 @@ pub use wgpu::{
     PushConstantRange, RenderPassColorAttachment, RenderPassDepthStencilAttachment,
     RenderPassDescriptor, RenderPipelineDescriptor as RawRenderPipelineDescriptor,
     Sampler as WgpuSampler, SamplerBindingType, SamplerBindingType as WgpuSamplerBindingType,
-    SamplerDescriptor, ShaderModule, ShaderModuleDescriptor, ShaderSource, ShaderStages,
-    StencilFaceState, StencilOperation, StencilState, StorageTextureAccess, StoreOp,
+    SamplerBorderColor, SamplerDescriptor, ShaderModule, ShaderModuleDescriptor, ShaderSource,
+    ShaderStages, StencilFaceState, StencilOperation, StencilState, StorageTextureAccess, StoreOp,
     TexelCopyBufferInfo, TexelCopyBufferLayout, TexelCopyTextureInfo, TextureAspect,
     TextureDescriptor, TextureDimension, TextureFormat, TextureFormatFeatureFlags,
     TextureFormatFeatures, TextureSampleType, TextureUsages, TextureView as WgpuTextureView,

examples/2d/bloom_2d.rs

@@ -110,6 +110,7 @@ fn update_bloom_settings(
                 bloom.prefilter.threshold_softness
             ));
             text.push_str(&format!("(I/K) Horizontal Scale: {:.2}\n", bloom.scale.x));
+            text.push_str(&format!("(P) High quality: {}\n", bloom.high_quality));
 
             if keycode.just_pressed(KeyCode::Space) {
                 commands.entity(camera_entity).remove::<Bloom>();
@@ -180,6 +181,10 @@ fn update_bloom_settings(
                 bloom.scale.x += dt * 2.0;
             }
             bloom.scale.x = bloom.scale.x.clamp(0.0, 16.0);
+
+            if keycode.just_pressed(KeyCode::KeyP) {
+                bloom.high_quality = !bloom.high_quality;
+            }
         }
 
         None => {

examples/3d/bloom_3d.rs

@@ -134,7 +134,8 @@ fn update_bloom_settings(
                 "(U/J) Threshold softness: {:.2}\n",
                 bloom.prefilter.threshold_softness
             ));
-            text.push_str(&format!("(I/K) Horizontal Scale: {:.2}\n", bloom.scale.x));
+            text.push_str(&format!("(I/K) Horizontal scale: {:.2}\n", bloom.scale.x));
+            text.push_str(&format!("(P) High quality: {}\n", bloom.high_quality));
 
             if keycode.just_pressed(KeyCode::Space) {
                 commands.entity(entity).remove::<Bloom>();
@@ -205,6 +206,10 @@ fn update_bloom_settings(
                 bloom.scale.x += dt * 2.0;
             }
             bloom.scale.x = bloom.scale.x.clamp(0.0, 8.0);
+
+            if keycode.just_pressed(KeyCode::KeyP) {
+                bloom.high_quality = !bloom.high_quality;
+            }
         }
 
         (entity, None) => {

release-content/release-notes/faster_bloom.md

@@ -0,0 +1,7 @@
+---
+title: Add a faster bloom implementation.
+authors: ["@beicause"]
+pull_requests: [21340]
+---
+
+Bloom now has a `high_quality` (default: true) option to control whether to use a high quality implementation, or a faster but lower quality implementation. The lower quality bloom still maintains reasonable visual quality while significantly reducing texture sampling. For low-end devices, this could potentially reduce frame time by a few milliseconds.