Revert Screen Space Transmission Gate for Mesh Bind Groups (#24089)

# Objective

- Alongside #24086, helps with #24084, although I think we should double
check any other added conditionals for bind group entries to make sure
they are accurate.

## Solution
So, originally the `SCREEN_SPACE_TRANSMISSION` was enabled with
`key.intersects(MeshPipelineKey::SCREEN_SPACE_SPECULAR_TRANSMISSION_RESERVED_BITS)`.
However, a low quality transmission would make this false, since low’s
MeshPipelineKey is configured like this: `const
SCREEN_SPACE_SPECULAR_TRANSMISSION_LOW = 0 <<
Self::SCREEN_SPACE_SPECULAR_TRANSMISSION_SHIFT_BITS;`. So, a
ScreenSpaceTransmission with Low Quality would break rendering (since
another if-block merely checks that the `ScreenSpaceTransmission`
component exists)

Making it so that the low transmission truly does *not* include the
view_transmission_textures makes the transmission render not properly -
the spheres disappear!

So, I think the proper fix here is to remove the gating around
transmission textures.
Edit: Another potential fix is to change the condition of the
`intersects` but I’m not sure how to encode what we want unless we want
to add another bit for `ScreenSpaceTransmission` component exists
essentially? Happy to close this PR if that is an acceptable direction.

## Testing

`cargo run --example transmission` works for all quality levels.

crates/bevy_pbr/src/deferred/mod.rs

@@ -290,9 +290,6 @@ impl SpecializedRenderPipeline for DeferredLightingLayout {
         if key.contains(MeshPipelineKey::ATMOSPHERE) {
             shader_defs.push("ATMOSPHERE".into());
         }
-        if key.intersects(MeshPipelineKey::SCREEN_SPACE_SPECULAR_TRANSMISSION_RESERVED_BITS) {
-            shader_defs.push("SCREEN_SPACE_TRANSMISSION".into());
-        }
         shader_defs.push("STANDARD_MATERIAL_CLEARCOAT".into());
 
         // Always true, since we're in the deferred lighting pipeline

crates/bevy_pbr/src/render/mesh.rs

@@ -3555,10 +3555,6 @@ impl SpecializedMeshPipeline for MeshPipeline {
             shader_defs.push("SHADOW_FILTER_METHOD_TEMPORAL".into());
         }
 
-        if key.intersects(MeshPipelineKey::SCREEN_SPACE_SPECULAR_TRANSMISSION_RESERVED_BITS) {
-            shader_defs.push("SCREEN_SPACE_TRANSMISSION".into());
-        }
-
         let blur_quality =
             key.intersection(MeshPipelineKey::SCREEN_SPACE_SPECULAR_TRANSMISSION_RESERVED_BITS);
 

crates/bevy_pbr/src/render/mesh_view_bindings.rs

@@ -1,7 +1,6 @@
 use crate::{
-    AreaLightLuts, DfgLut, ScreenSpaceTransmission, ViewEnvironmentMapUniformOffset,
-    ViewFogUniformOffset, ViewLightProbesUniformOffset, ViewLightsUniformOffset,
-    ViewScreenSpaceReflectionsUniformOffset,
+    AreaLightLuts, DfgLut, ViewEnvironmentMapUniformOffset, ViewFogUniformOffset,
+    ViewLightProbesUniformOffset, ViewLightsUniformOffset, ViewScreenSpaceReflectionsUniformOffset,
 };
 use bevy_core_pipeline::{
     oit::{
@@ -94,10 +93,9 @@ bitflags::bitflags! {
         const SCREEN_SPACE_AMBIENT_OCCLUSION   = 1 << 10;
         const IRRADIANCE_VOLUME                = 1 << 11;
         const SCREEN_SPACE_REFLECTIONS         = 1 << 12;
-        const SCREEN_SPACE_TRANSMISSION        = 1 << 13;
-        const CONTACT_SHADOWS                  = 1 << 14;
-        const DISTANCE_FOG                     = 1 << 15;
-        const AREA_LIGHT_LUTS                         = 1 << 16;
+        const CONTACT_SHADOWS                  = 1 << 13;
+        const DISTANCE_FOG                     = 1 << 14;
+        const AREA_LIGHT_LUTS                  = 1 << 15;
     }
 }
 
@@ -170,9 +168,6 @@ impl From<MeshPipelineKey> for MeshPipelineViewLayoutKey {
         if value.contains(MeshPipelineKey::SCREEN_SPACE_REFLECTIONS) {
             result |= MeshPipelineViewLayoutKey::SCREEN_SPACE_REFLECTIONS;
         }
-        if value.intersects(MeshPipelineKey::SCREEN_SPACE_SPECULAR_TRANSMISSION_RESERVED_BITS) {
-            result |= MeshPipelineViewLayoutKey::SCREEN_SPACE_TRANSMISSION;
-        }
         if value.contains(MeshPipelineKey::CONTACT_SHADOWS) {
             result |= MeshPipelineViewLayoutKey::CONTACT_SHADOWS;
         }
@@ -408,16 +403,14 @@ fn layout_entries(
         }
     }
 
-    if layout_key.contains(MeshPipelineViewLayoutKey::SCREEN_SPACE_TRANSMISSION) {
-        // View Transmission Texture
-        entries = entries.extend_with_indices((
-            (
-                25,
-                texture_2d(TextureSampleType::Float { filterable: true }),
-            ),
-            (26, sampler(SamplerBindingType::Filtering)),
-        ));
-    }
+    // View Transmission Texture
+    entries = entries.extend_with_indices((
+        (
+            25,
+            texture_2d(TextureSampleType::Float { filterable: true }),
+        ),
+        (26, sampler(SamplerBindingType::Filtering)),
+    ));
 
     // OIT
     if layout_key.contains(MeshPipelineViewLayoutKey::OIT_ENABLED) {
@@ -649,7 +642,7 @@ pub fn prepare_mesh_view_bind_groups(
             Option<&RenderViewLightProbes<EnvironmentMapLight>>,
             Option<&RenderViewLightProbes<IrradianceVolume>>,
         ),
-        (Has<ExtractedAtmosphere>, Has<ScreenSpaceTransmission>),
+        Has<ExtractedAtmosphere>,
         (
             &ViewUniformOffset,
             &ViewLightsUniformOffset,
@@ -728,7 +721,7 @@ pub fn prepare_mesh_view_bind_groups(
             atmosphere_textures,
             tonemapping,
             (render_view_environment_maps, render_view_irradiance_volumes),
-            (has_atmosphere, has_transmission),
+            has_atmosphere,
             (
                 view_uniform_offset,
                 view_lights_offset,
@@ -869,19 +862,16 @@ pub fn prepare_mesh_view_bind_groups(
                 entries = entries.extend_with_indices(((17, ssao_view),));
             }
 
-            if has_transmission {
-                layout_key |= MeshPipelineViewLayoutKey::SCREEN_SPACE_TRANSMISSION;
-                let transmission_view = transmission_texture
-                    .map(|transmission| &transmission.view)
-                    .unwrap_or(&fallback_image_zero.texture_view);
+            let transmission_view = transmission_texture
+                .map(|transmission| &transmission.view)
+                .unwrap_or(&fallback_image_zero.texture_view);
 
-                let transmission_sampler = transmission_texture
-                    .map(|transmission| &transmission.sampler)
-                    .unwrap_or(&fallback_image_zero.sampler);
+            let transmission_sampler = transmission_texture
+                .map(|transmission| &transmission.sampler)
+                .unwrap_or(&fallback_image_zero.sampler);
 
-                entries = entries
-                    .extend_with_indices(((25, transmission_view), (26, transmission_sampler)));
-            }
+            entries =
+                entries.extend_with_indices(((25, transmission_view), (26, transmission_sampler)));
 
             // When using WebGL, we can't have a multisampled texture with `TEXTURE_BINDING`
             // See https://github.com/gfx-rs/wgpu/issues/5263

crates/bevy_pbr/src/render/mesh_view_bindings.wgsl

@@ -103,10 +103,8 @@ const VISIBILITY_RANGE_UNIFORM_BUFFER_SIZE: u32 = 64u;
 @group(0) @binding(24) var deferred_prepass_texture: texture_2d<u32>;
 #endif // DEFERRED_PREPASS
 
-#ifdef SCREEN_SPACE_TRANSMISSION
 @group(0) @binding(25) var view_transmission_texture: texture_2d<f32>;
 @group(0) @binding(26) var view_transmission_sampler: sampler;
-#endif
 
 #ifdef OIT_ENABLED
 @group(0) @binding(27) var<uniform> oit_settings: types::OrderIndependentTransparencySettings;