Contact Shadows

crates/bevy_pbr/src/contact_shadows.rs

@@ -0,0 +1,140 @@
+//! Contact shadows implemented via screenspace raymarching.
+
+use bevy_app::{App, Plugin};
+use bevy_derive::{Deref, DerefMut};
+use bevy_ecs::{
+    component::Component,
+    entity::Entity,
+    query::{QueryItem, With},
+    reflect::ReflectComponent,
+    resource::Resource,
+    schedule::IntoScheduleConfigs,
+    system::{Commands, Query, Res, ResMut},
+};
+use bevy_reflect::{std_traits::ReflectDefault, Reflect};
+use bevy_render::{
+    extract_component::{ExtractComponent, ExtractComponentPlugin},
+    render_resource::{DynamicUniformBuffer, ShaderType},
+    renderer::{RenderDevice, RenderQueue},
+    view::ExtractedView,
+    Render, RenderApp, RenderSystems,
+};
+use bevy_utils::default;
+
+/// Enables contact shadows for a camera.
+pub struct ContactShadowsPlugin;
+
+/// Add this component to a camera to enable contact shadows.
+///
+/// Contact shadows are a screen-space technique that adds small-scale shadows
+/// in areas where traditional shadow maps may lack detail, such as where
+/// objects touch the ground.
+///
+/// This can be used in forward or deferred rendering, but the depth prepass is required.
+#[derive(Clone, Copy, Component, Reflect)]
+#[reflect(Component, Default, Clone)]
+#[require(bevy_core_pipeline::prepass::DepthPrepass)]
+pub struct ContactShadows {
+    /// The number of steps to be taken at regular intervals to find an initial
+    /// intersection.
+    pub linear_steps: u32,
+    /// When marching the depth buffer, we only have 2.5D information and don't
+    /// know how thick surfaces are. We shall assume that the depth buffer
+    /// fragments are cuboids with a constant thickness defined by this
+    /// parameter.
+    pub thickness: f32,
+    /// The length of the contact shadow ray in world space.
+    pub length: f32,
+}
+
+impl Default for ContactShadows {
+    fn default() -> Self {
+        Self {
+            linear_steps: 16,
+            thickness: 0.1,
+            length: 0.3,
+        }
+    }
+}
+
+/// A version of [`ContactShadows`] for upload to the GPU.
+#[derive(Clone, Copy, Component, ShaderType, Default)]
+pub struct ContactShadowsUniform {
+    pub linear_steps: u32,
+    pub thickness: f32,
+    pub length: f32,
+}
+
+impl From<ContactShadows> for ContactShadowsUniform {
+    fn from(settings: ContactShadows) -> Self {
+        Self {
+            linear_steps: settings.linear_steps,
+            thickness: settings.thickness,
+            length: settings.length,
+        }
+    }
+}
+
+impl ExtractComponent for ContactShadows {
+    type QueryData = &'static ContactShadows;
+    type QueryFilter = ();
+    type Out = ContactShadows;
+
+    fn extract_component(settings: QueryItem<'_, '_, Self::QueryData>) -> Option<Self::Out> {
+        Some(*settings)
+    }
+}
+
+/// A GPU buffer that stores the contact shadow settings for each view.
+#[derive(Resource, Default)]
+pub struct ContactShadowsBuffer(pub DynamicUniformBuffer<ContactShadowsUniform>);
+
+impl Plugin for ContactShadowsPlugin {
+    fn build(&self, app: &mut App) {
+        app.register_type::<ContactShadows>()
+            .add_plugins(ExtractComponentPlugin::<ContactShadows>::default());
+
+        let Some(render_app) = app.get_sub_app_mut(RenderApp) else {
+            return;
+        };
+
+        render_app
+            .init_resource::<ContactShadowsBuffer>()
+            .add_systems(
+                Render,
+                prepare_contact_shadows_settings.in_set(RenderSystems::PrepareResources),
+            );
+    }
+}
+
+fn prepare_contact_shadows_settings(
+    mut commands: Commands,
+    views: Query<(Entity, Option<&ContactShadows>), With<ExtractedView>>,
+    mut contact_shadows_buffer: ResMut<ContactShadowsBuffer>,
+    render_device: Res<RenderDevice>,
+    render_queue: Res<RenderQueue>,
+) {
+    contact_shadows_buffer.0.clear();
+    for (entity, settings) in &views {
+        let uniform = if let Some(settings) = settings {
+            ContactShadowsUniform::from(*settings)
+        } else {
+            ContactShadowsUniform {
+                linear_steps: 0,
+                ..default()
+            }
+        };
+        let offset = contact_shadows_buffer.0.push(&uniform);
+        commands
+            .entity(entity)
+            .insert(ViewContactShadowsUniformOffset(offset));
+    }
+    contact_shadows_buffer
+        .0
+        .write_buffer(&render_device, &render_queue);
+}
+
+/// A component that stores the offset within the [`ContactShadowsBuffer`] for
+/// each view.
+#[derive(Component, Default, Deref, DerefMut)]
+pub struct ViewContactShadowsUniformOffset(pub u32);

crates/bevy_pbr/src/deferred/mod.rs

@@ -1,8 +1,9 @@
 use crate::{
     graph::NodePbr, MeshPipeline, MeshViewBindGroup, RenderViewLightProbes,
-    ScreenSpaceAmbientOcclusion, ScreenSpaceReflectionsUniform, ViewEnvironmentMapUniformOffset,
-    ViewLightProbesUniformOffset, ViewScreenSpaceReflectionsUniformOffset,
-    TONEMAPPING_LUT_SAMPLER_BINDING_INDEX, TONEMAPPING_LUT_TEXTURE_BINDING_INDEX,
+    ScreenSpaceAmbientOcclusion, ScreenSpaceReflectionsUniform, ViewContactShadowsUniformOffset,
+    ViewEnvironmentMapUniformOffset, ViewLightProbesUniformOffset,
+    ViewScreenSpaceReflectionsUniformOffset, TONEMAPPING_LUT_SAMPLER_BINDING_INDEX,
+    TONEMAPPING_LUT_TEXTURE_BINDING_INDEX,
 };
 use crate::{
     DistanceFog, ExtractedAtmosphere, MeshPipelineKey, ViewFogUniformOffset,
@@ -139,6 +140,7 @@ impl ViewNode for DeferredOpaquePass3dPbrLightingNode {
         &'static ViewFogUniformOffset,
         &'static ViewLightProbesUniformOffset,
         &'static ViewScreenSpaceReflectionsUniformOffset,
+        &'static ViewContactShadowsUniformOffset,
         &'static ViewEnvironmentMapUniformOffset,
         &'static MeshViewBindGroup,
         &'static ViewTarget,
@@ -156,6 +158,7 @@ impl ViewNode for DeferredOpaquePass3dPbrLightingNode {
             view_fog_offset,
             view_light_probes_offset,
             view_ssr_offset,
+            view_contact_shadows_offset,
             view_environment_map_offset,
             mesh_view_bind_group,
             target,
@@ -215,6 +218,7 @@ impl ViewNode for DeferredOpaquePass3dPbrLightingNode {
                 view_fog_offset.offset,
                 **view_light_probes_offset,
                 **view_ssr_offset,
+                **view_contact_shadows_offset,
                 **view_environment_map_offset,
             ],
         );

crates/bevy_pbr/src/lib.rs

@@ -27,6 +27,11 @@ pub mod experimental {
 mod atmosphere;
 mod cluster;
 mod components;
+pub mod contact_shadows;
+pub use contact_shadows::{
+    ContactShadows, ContactShadowsBuffer, ContactShadowsPlugin, ContactShadowsUniform,
+    ViewContactShadowsUniformOffset,
+};
 pub mod decal;
 pub mod deferred;
 pub mod diagnostic;
@@ -79,6 +84,7 @@ pub use volumetric_fog::VolumetricFogPlugin;
 pub mod prelude {
     #[doc(hidden)]
     pub use crate::{
+        contact_shadows::ContactShadowsPlugin,
         fog::{DistanceFog, FogFalloff},
         material::{Material, MaterialPlugin},
         mesh_material::MeshMaterial3d,
@@ -153,8 +159,8 @@ fn shader_ref(path: PathBuf) -> ShaderRef {
     ShaderRef::Path(AssetPath::from_path_buf(path).with_source("embedded"))
 }
 
-pub const TONEMAPPING_LUT_TEXTURE_BINDING_INDEX: u32 = 18;
-pub const TONEMAPPING_LUT_SAMPLER_BINDING_INDEX: u32 = 19;
+pub const TONEMAPPING_LUT_TEXTURE_BINDING_INDEX: u32 = 19;
+pub const TONEMAPPING_LUT_SAMPLER_BINDING_INDEX: u32 = 20;
 
 /// Sets up the entire PBR infrastructure of bevy.
 pub struct PbrPlugin {
@@ -241,6 +247,7 @@ impl Plugin for PbrPlugin {
                 VolumetricFogPlugin,
                 ScreenSpaceReflectionsPlugin,
                 ClusteredDecalPlugin,
+                ContactShadowsPlugin,
             ))
             .add_plugins((
                 decal::ForwardDecalPlugin,

crates/bevy_pbr/src/render/mesh.rs

@@ -1,3 +1,4 @@
+use crate::contact_shadows::ViewContactShadowsUniformOffset;
 use crate::{
     material_bind_groups::{MaterialBindGroupIndex, MaterialBindGroupSlot},
     resources::write_atmosphere_buffer,
@@ -2997,6 +2998,7 @@ impl<P: PhaseItem, const I: usize> RenderCommand<P> for SetMeshViewBindGroup<I>
         Read<ViewFogUniformOffset>,
         Read<ViewLightProbesUniformOffset>,
         Read<ViewScreenSpaceReflectionsUniformOffset>,
+        Read<ViewContactShadowsUniformOffset>,
         Read<ViewEnvironmentMapUniformOffset>,
         Read<MeshViewBindGroup>,
         Option<Read<OrderIndependentTransparencySettingsOffset>>,
@@ -3012,6 +3014,7 @@ impl<P: PhaseItem, const I: usize> RenderCommand<P> for SetMeshViewBindGroup<I>
             view_fog,
             view_light_probes,
             view_ssr,
+            view_contact_shadows,
             view_environment_map,
             mesh_view_bind_group,
             maybe_oit_layers_count_offset,
@@ -3026,6 +3029,7 @@ impl<P: PhaseItem, const I: usize> RenderCommand<P> for SetMeshViewBindGroup<I>
             view_fog.offset,
             **view_light_probes,
             **view_ssr,
+            **view_contact_shadows,
             **view_environment_map,
         ];
         if let Some(layers_count_offset) = maybe_oit_layers_count_offset {