Apply codebase changes in preparation for StandardMaterial transmis…

…sion (#8704)

# Objective

- Make #8015 easier to review;

## Solution

- This commit contains changes not directly related to transmission
required by #8015, in easier-to-review, one-change-per-commit form.

---

## Changelog

### Fixed

- Clear motion vector prepass using `0.0` instead of `1.0`, to avoid TAA
artifacts on transparent objects against the background;

### Added

- The `E` mathematical constant is now available for use in shaders,
exposed under `bevy_pbr::utils`;
- A new `TAA` shader def is now available, for conditionally enabling
shader logic via `#ifdef` when TAA is enabled; (e.g. for jittering
texture samples)
- A new `FallbackImageZero` resource is introduced, for when a fallback
image filled with zeroes is required;
- A new `RenderPhase<I>::render_range()` method is introduced, for
render phases that need to render their items in multiple parceled out
“steps”;

### Changed

- The `MainTargetTextures` struct now holds both `Texture` and
`TextureViews` for the main textures;
- The fog shader functions under `bevy_pbr::fog` now take the a `Fog`
structure as their first argument, instead of relying on the global
`fog` uniform;
- The main textures can now be used as copy sources;

## Migration Guide

- `ViewTarget::main_texture()` and `ViewTarget::main_texture_other()`
now return `&Texture` instead of `&TextureView`. If you were relying on
these methods, replace your usage with
`ViewTarget::main_texture_view()`and
`ViewTarget::main_texture_other_view()`, respectively;
- `ViewTarget::sampled_main_texture()` now returns `Option<&Texture>`
instead of a `Option<&TextureView>`. If you were relying on this method,
replace your usage with `ViewTarget::sampled_main_texture_view()`;
- The `apply_fog()`, `linear_fog()`, `exponential_fog()`,
`exponential_squared_fog()` and `atmospheric_fog()` functions now take a
configurable `Fog` struct. If you were relying on them, update your
usage by adding the global `fog` uniform as their first argument;

crates/bevy_core_pipeline/src/bloom/mod.rs

@@ -177,7 +177,9 @@ impl ViewNode for BloomNode {
                             BindGroupEntry {
                                 binding: 0,
                                 // Read from main texture directly
-                                resource: BindingResource::TextureView(view_target.main_texture()),
+                                resource: BindingResource::TextureView(
+                                    view_target.main_texture_view(),
+                                ),
                             },
                             BindGroupEntry {
                                 binding: 1,

crates/bevy_core_pipeline/src/prepass/node.rs

@@ -67,9 +67,10 @@ impl ViewNode for PrepassNode {
                 view: &view_motion_vectors_texture.default_view,
                 resolve_target: None,
                 ops: Operations {
-                    // Blue channel doesn't matter, but set to 1.0 for possible faster clear
+                    // Red and Green channels are X and Y components of the motion vectors
+                    // Blue channel doesn't matter, but set to 0.0 for possible faster clear
                     // https://gpuopen.com/performance/#clears
-                    load: LoadOp::Clear(Color::rgb_linear(1.0, 1.0, 1.0).into()),
+                    load: LoadOp::Clear(Color::rgb_linear(0.0, 0.0, 0.0).into()),
                     store: true,
                 },
             },

crates/bevy_core_pipeline/src/upscaling/node.rs

@@ -47,7 +47,7 @@ impl ViewNode for UpscalingNode {
             LoadOp::Clear(Default::default())
         };
 
-        let upscaled_texture = target.main_texture();
+        let upscaled_texture = target.main_texture_view();
 
         let mut cached_bind_group = self.cached_texture_bind_group.lock().unwrap();
         let bind_group = match &mut *cached_bind_group {

crates/bevy_pbr/src/material.rs

@@ -7,6 +7,7 @@ use bevy_app::{App, Plugin};
 use bevy_asset::{AddAsset, AssetEvent, AssetServer, Assets, Handle};
 use bevy_core_pipeline::{
     core_3d::{AlphaMask3d, Opaque3d, Transparent3d},
+    experimental::taa::TemporalAntiAliasSettings,
     prepass::NormalPrepass,
     tonemapping::{DebandDither, Tonemapping},
 };
@@ -387,6 +388,7 @@ pub fn queue_material_meshes<M: Material>(
         Option<&DebandDither>,
         Option<&EnvironmentMapLight>,
         Option<&NormalPrepass>,
+        Option<&TemporalAntiAliasSettings>,
         &mut RenderPhase<Opaque3d>,
         &mut RenderPhase<AlphaMask3d>,
         &mut RenderPhase<Transparent3d>,
@@ -401,6 +403,7 @@ pub fn queue_material_meshes<M: Material>(
         dither,
         environment_map,
         normal_prepass,
+        taa_settings,
         mut opaque_phase,
         mut alpha_mask_phase,
         mut transparent_phase,
@@ -417,6 +420,10 @@ pub fn queue_material_meshes<M: Material>(
             view_key |= MeshPipelineKey::NORMAL_PREPASS;
         }
 
+        if taa_settings.is_some() {
+            view_key |= MeshPipelineKey::TAA;
+        }
+
         let environment_map_loaded = match environment_map {
             Some(environment_map) => environment_map.is_loaded(&images),
             None => false,

crates/bevy_pbr/src/render/fog.wgsl

@@ -6,61 +6,66 @@
 // https://iquilezles.org/articles/fog/ (Atmospheric Fog and Scattering)
 
 fn scattering_adjusted_fog_color(
+    fog_params: Fog,
     scattering: vec3<f32>,
 ) -> vec4<f32> {
-    if (fog.directional_light_color.a > 0.0) {
+    if (fog_params.directional_light_color.a > 0.0) {
         return vec4<f32>(
-            fog.base_color.rgb
-                + scattering * fog.directional_light_color.rgb * fog.directional_light_color.a,
-            fog.base_color.a,
+            fog_params.base_color.rgb
+                + scattering * fog_params.directional_light_color.rgb * fog_params.directional_light_color.a,
+            fog_params.base_color.a,
         );
     } else {
-        return fog.base_color;
+        return fog_params.base_color;
     }
 }
 
 fn linear_fog(
+    fog_params: Fog,
     input_color: vec4<f32>,
     distance: f32,
     scattering: vec3<f32>,
 ) -> vec4<f32> {
-    var fog_color = scattering_adjusted_fog_color(scattering);
-    let start = fog.be.x;
-    let end = fog.be.y;
+    var fog_color = scattering_adjusted_fog_color(fog_params, scattering);
+    let start = fog_params.be.x;
+    let end = fog_params.be.y;
     fog_color.a *= 1.0 - clamp((end - distance) / (end - start), 0.0, 1.0);
     return vec4<f32>(mix(input_color.rgb, fog_color.rgb, fog_color.a), input_color.a);
 }
 
 fn exponential_fog(
+    fog_params: Fog,
     input_color: vec4<f32>,
     distance: f32,
     scattering: vec3<f32>,
 ) -> vec4<f32> {
-    var fog_color = scattering_adjusted_fog_color(scattering);
-    let density = fog.be.x;
+    var fog_color = scattering_adjusted_fog_color(fog_params, scattering);
+    let density = fog_params.be.x;
     fog_color.a *= 1.0 - 1.0 / exp(distance * density);
     return vec4<f32>(mix(input_color.rgb, fog_color.rgb, fog_color.a), input_color.a);
 }
 
 fn exponential_squared_fog(
+    fog_params: Fog,
     input_color: vec4<f32>,
     distance: f32,
     scattering: vec3<f32>,
 ) -> vec4<f32> {
-    var fog_color = scattering_adjusted_fog_color(scattering);
-    let distance_times_density = distance * fog.be.x;
+    var fog_color = scattering_adjusted_fog_color(fog_params, scattering);
+    let distance_times_density = distance * fog_params.be.x;
     fog_color.a *= 1.0 - 1.0 / exp(distance_times_density * distance_times_density);
     return vec4<f32>(mix(input_color.rgb, fog_color.rgb, fog_color.a), input_color.a);
 }
 
 fn atmospheric_fog(
+    fog_params: Fog,
     input_color: vec4<f32>,
     distance: f32,
     scattering: vec3<f32>,
 ) -> vec4<f32> {
-    var fog_color = scattering_adjusted_fog_color(scattering);
-    let extinction_factor = 1.0 - 1.0 / exp(distance * fog.be);
-    let inscattering_factor = 1.0 - 1.0 / exp(distance * fog.bi);
+    var fog_color = scattering_adjusted_fog_color(fog_params, scattering);
+    let extinction_factor = 1.0 - 1.0 / exp(distance * fog_params.be);
+    let inscattering_factor = 1.0 - 1.0 / exp(distance * fog_params.bi);
     return vec4<f32>(
         input_color.rgb * (1.0 - extinction_factor * fog_color.a)
             + fog_color.rgb * inscattering_factor * fog_color.a,

crates/bevy_pbr/src/render/mesh.rs

@@ -586,6 +586,7 @@ bitflags::bitflags! {
                                                             // See: https://www.khronos.org/opengl/wiki/Early_Fragment_Test
         const ENVIRONMENT_MAP                   = (1 << 7);
         const DEPTH_CLAMP_ORTHO                 = (1 << 8);
+        const TAA                               = (1 << 9);
         const BLEND_RESERVED_BITS               = Self::BLEND_MASK_BITS << Self::BLEND_SHIFT_BITS; // ← Bitmask reserving bits for the blend state
         const BLEND_OPAQUE                      = (0 << Self::BLEND_SHIFT_BITS);                   // ← Values are just sequential within the mask, and can range from 0 to 3
         const BLEND_PREMULTIPLIED_ALPHA         = (1 << Self::BLEND_SHIFT_BITS);                   //
@@ -804,6 +805,10 @@ impl SpecializedMeshPipeline for MeshPipeline {
             shader_defs.push("ENVIRONMENT_MAP".into());
         }
 
+        if key.contains(MeshPipelineKey::TAA) {
+            shader_defs.push("TAA".into());
+        }
+
         let format = if key.contains(MeshPipelineKey::HDR) {
             ViewTarget::TEXTURE_FORMAT_HDR
         } else {

crates/bevy_pbr/src/render/pbr.wgsl

@@ -133,7 +133,7 @@ fn fragment(in: FragmentInput) -> @location(0) vec4<f32> {
 
     // fog
     if (fog.mode != FOG_MODE_OFF && (material.flags & STANDARD_MATERIAL_FLAGS_FOG_ENABLED_BIT) != 0u) {
-        output_color = apply_fog(output_color, in.world_position.xyz, view.world_position.xyz);
+        output_color = apply_fog(fog, output_color, in.world_position.xyz, view.world_position.xyz);
     }
 
 #ifdef TONEMAP_IN_SHADER

crates/bevy_pbr/src/render/pbr_functions.wgsl

@@ -275,7 +275,7 @@ fn pbr(
 #endif // PREPASS_FRAGMENT
 
 #ifndef PREPASS_FRAGMENT
-fn apply_fog(input_color: vec4<f32>, fragment_world_position: vec3<f32>, view_world_position: vec3<f32>) -> vec4<f32> {
+fn apply_fog(fog_params: Fog, input_color: vec4<f32>, fragment_world_position: vec3<f32>, view_world_position: vec3<f32>) -> vec4<f32> {
     let view_to_world = fragment_world_position.xyz - view_world_position.xyz;
 
     // `length()` is used here instead of just `view_to_world.z` since that produces more
@@ -285,7 +285,7 @@ fn apply_fog(input_color: vec4<f32>, fragment_world_position: vec3<f32>, view_wo
     let distance = length(view_to_world);
 
     var scattering = vec3<f32>(0.0);
-    if fog.directional_light_color.a > 0.0 {
+    if fog_params.directional_light_color.a > 0.0 {
         let view_to_world_normalized = view_to_world / distance;
         let n_directional_lights = lights.n_directional_lights;
         for (var i: u32 = 0u; i < n_directional_lights; i = i + 1u) {
@@ -295,19 +295,19 @@ fn apply_fog(input_color: vec4<f32>, fragment_world_position: vec3<f32>, view_wo
                     dot(view_to_world_normalized, light.direction_to_light),
                     0.0
                 ),
-                fog.directional_light_exponent
+                fog_params.directional_light_exponent
             ) * light.color.rgb;
         }
     }
 
-    if fog.mode == FOG_MODE_LINEAR {
-        return linear_fog(input_color, distance, scattering);
-    } else if fog.mode == FOG_MODE_EXPONENTIAL {
-        return exponential_fog(input_color, distance, scattering);
-    } else if fog.mode == FOG_MODE_EXPONENTIAL_SQUARED {
-        return exponential_squared_fog(input_color, distance, scattering);
-    } else if fog.mode == FOG_MODE_ATMOSPHERIC {
-        return atmospheric_fog(input_color, distance, scattering);
+    if fog_params.mode == FOG_MODE_LINEAR {
+        return linear_fog(fog_params, input_color, distance, scattering);
+    } else if fog_params.mode == FOG_MODE_EXPONENTIAL {
+        return exponential_fog(fog_params, input_color, distance, scattering);
+    } else if fog_params.mode == FOG_MODE_EXPONENTIAL_SQUARED {
+        return exponential_squared_fog(fog_params, input_color, distance, scattering);
+    } else if fog_params.mode == FOG_MODE_ATMOSPHERIC {
+        return atmospheric_fog(fog_params, input_color, distance, scattering);
     } else {
         return input_color;
     }

crates/bevy_pbr/src/render/utils.wgsl

@@ -1,6 +1,7 @@
 #define_import_path bevy_pbr::utils
 
 const PI: f32 = 3.141592653589793;
+const E: f32 = 2.718281828459045;
 
 fn hsv2rgb(hue: f32, saturation: f32, value: f32) -> vec3<f32> {
     let rgb = clamp(

crates/bevy_render/src/render_phase/mod.rs

@@ -89,6 +89,29 @@ impl<I: PhaseItem> RenderPhase<I> {
             draw_function.draw(world, render_pass, view, item);
         }
     }
+
+    /// Renders all [`PhaseItem`]s in the provided `range` (based on their index in `self.items`) using their corresponding draw functions.
+    pub fn render_range<'w>(
+        &self,
+        render_pass: &mut TrackedRenderPass<'w>,
+        world: &'w World,
+        view: Entity,
+        range: Range<usize>,
+    ) {
+        let draw_functions = world.resource::<DrawFunctions<I>>();
+        let mut draw_functions = draw_functions.write();
+        draw_functions.prepare(world);
+
+        for item in self
+            .items
+            .get(range)
+            .expect("`Range` provided to `render_range()` is out of bounds")
+            .iter()
+        {
+            let draw_function = draw_functions.get_mut(item.draw_function()).unwrap();
+            draw_function.draw(world, render_pass, view, item);
+        }
+    }
 }
 
 impl<I: BatchedPhaseItem> RenderPhase<I> {

crates/bevy_render/src/texture/fallback_image.rs

@@ -17,10 +17,21 @@ use crate::{
 /// A [`RenderApp`](crate::RenderApp) resource that contains the default "fallback image",
 /// which can be used in situations where an image was not explicitly defined. The most common
 /// use case is [`AsBindGroup`] implementations (such as materials) that support optional textures.
-/// [`FallbackImage`] defaults to a 1x1 fully white texture, making blending colors with it a no-op.
+///
+/// Defaults to a 1x1 fully opaque white texture, (1.0, 1.0, 1.0, 1.0) which makes multiplying
+/// it with other colors a no-op.
 #[derive(Resource, Deref)]
 pub struct FallbackImage(GpuImage);
 
+/// A [`RenderApp`](crate::RenderApp) resource that contains a _zero-filled_ "fallback image",
+/// which can be used in place of [`FallbackImage`], when a fully transparent or black fallback
+/// is required instead of fully opaque white.
+///
+/// Defaults to a 1x1 fully transparent black texture, (0.0, 0.0, 0.0, 0.0) which makes adding
+/// or alpha-blending it to other colors a no-op.
+#[derive(Resource, Deref)]
+pub struct FallbackImageZero(GpuImage);
+
 /// A [`RenderApp`](crate::RenderApp) resource that contains a "cubemap fallback image",
 /// which can be used in situations where an image was not explicitly defined. The most common
 /// use case is [`AsBindGroup`] implementations (such as materials) that support optional textures.
@@ -34,9 +45,10 @@ fn fallback_image_new(
     format: TextureFormat,
     dimension: TextureViewDimension,
     samples: u32,
+    value: u8,
 ) -> GpuImage {
-    // TODO make this configurable
-    let data = vec![255; format.pixel_size()];
+    // TODO make this configurable per channel
+    let data = vec![value; format.pixel_size()];
 
     let extents = Extent3d {
         width: 1,
@@ -92,6 +104,24 @@ impl FromWorld for FallbackImage {
             TextureFormat::bevy_default(),
             TextureViewDimension::D2,
             1,
+            255,
+        ))
+    }
+}
+
+impl FromWorld for FallbackImageZero {
+    fn from_world(world: &mut bevy_ecs::prelude::World) -> Self {
+        let render_device = world.resource::<RenderDevice>();
+        let render_queue = world.resource::<RenderQueue>();
+        let default_sampler = world.resource::<DefaultImageSampler>();
+        Self(fallback_image_new(
+            render_device,
+            render_queue,
+            default_sampler,
+            TextureFormat::bevy_default(),
+            TextureViewDimension::D2,
+            1,
+            0,
         ))
     }
 }
@@ -108,6 +138,7 @@ impl FromWorld for FallbackImageCubemap {
             TextureFormat::bevy_default(),
             TextureViewDimension::Cube,
             1,
+            255,
         ))
     }
 }
@@ -148,6 +179,7 @@ impl<'w> FallbackImagesMsaa<'w> {
                 TextureFormat::bevy_default(),
                 TextureViewDimension::D2,
                 sample_count,
+                255,
             )
         })
     }
@@ -171,6 +203,7 @@ impl<'w> FallbackImagesDepth<'w> {
                 TextureFormat::Depth32Float,
                 TextureViewDimension::D2,
                 sample_count,
+                255,
             )
         })
     }

crates/bevy_render/src/texture/mod.rs

@@ -120,6 +120,7 @@ impl Plugin for ImagePlugin {
             render_app
                 .insert_resource(DefaultImageSampler(default_sampler))
                 .init_resource::<FallbackImage>()
+                .init_resource::<FallbackImageZero>()
                 .init_resource::<FallbackImageCubemap>()
                 .init_resource::<FallbackImageMsaaCache>()
                 .init_resource::<FallbackImageDepthCache>();