render: make shadow depth bias configurable per light source

examples/shadows/src/main.rs

@@ -124,13 +124,6 @@ fn setup_scene_plugin(game: &mut Game) {
     cube_gltf.wait_recurse_dependencies_load();
     let cube_mesh = &cube_gltf.data_ref().unwrap().scenes[0];
 
-    let platform_gltf = resman
-        .request::<Gltf>("../assets/wood-platform.glb")
-        .unwrap();
-
-    platform_gltf.wait_recurse_dependencies_load();
-    let platform_mesh = &platform_gltf.data_ref().unwrap().scenes[0];
-
     let palm_tree_platform_gltf = resman
         .request::<Gltf>("../assets/shadows-platform-palmtree.glb")
         .unwrap();
@@ -189,6 +182,10 @@ fn setup_scene_plugin(game: &mut Game) {
                 color: Vec3::new(1.0, 0.95, 0.9),
                 intensity: 0.9,
             },
+            ShadowCasterSettings {
+                filtering_mode: ShadowFilteringMode::Pcss,
+                ..Default::default()
+            },
             light_tran,
         ));
 

lyra-game/src/render/graph/passes/shadows.rs

@@ -256,7 +256,8 @@ impl ShadowMapsPass {
                     has_shadow_settings,
                     pcf_samples_num: u.pcf_samples_num,
                     pcss_blocker_search_samples: u.pcss_blocker_search_samples,
-                    _padding2: [0; 2],
+                    constant_depth_bias: DEFAULT_CONSTANT_DEPTH_BIAS * shadow_settings.constant_depth_bias_scale,
+                    _padding2: 0,
                 };
 
                 let uniform_index = self.light_uniforms_buffer.insert(queue, &u);
@@ -348,7 +349,8 @@ impl ShadowMapsPass {
                             has_shadow_settings,
                             pcf_samples_num: u.pcf_samples_num,
                             pcss_blocker_search_samples: u.pcss_blocker_search_samples,
-                            _padding2: [0; 2],
+                            constant_depth_bias: DEFAULT_CONSTANT_DEPTH_BIAS * shadow_settings.constant_depth_bias_scale,
+                            _padding2: 0,
                         },
                     );
                     indices[i] = uniform_i;
@@ -594,6 +596,11 @@ impl Node for ShadowMapsPass {
         }
         let settings = *world.get_resource::<ShadowCasterSettings>();
 
+        if settings.use_back_faces {
+            // TODO: shadow maps rendering with back faces
+            todo!("render with back faces");
+        }
+
         self.render_meshes = world.try_get_resource_data::<RenderMeshes>();
         self.transform_buffers = world.try_get_resource_data::<TransformBuffers>();
         self.mesh_buffers = world.try_get_resource_data::<RenderAssets<MeshBufferStorage>>();
@@ -888,8 +895,15 @@ pub struct ShadowCasterSettings {
     pub pcss_blocker_search_samples: u32,
     pub near_plane: f32,
     pub far_plane: f32,
+    /// The scale of the constant shadow depth bias.
+    /// 
+    /// This scale will be multiplied by the default constant depth bias value of 0.001.
+    pub constant_depth_bias_scale: f32,
+    pub use_back_faces: bool,
 }
 
+const DEFAULT_CONSTANT_DEPTH_BIAS: f32 = 0.001;
+
 impl Default for ShadowCasterSettings {
     fn default() -> Self {
         Self {
@@ -898,6 +912,8 @@ impl Default for ShadowCasterSettings {
             pcss_blocker_search_samples: 25,
             near_plane: 0.1,
             far_plane: 45.0,
+            constant_depth_bias_scale: 1.0,
+            use_back_faces: false,
         }
     }
 }
@@ -917,7 +933,8 @@ pub struct LightShadowUniform {
     has_shadow_settings: u32,
     pcf_samples_num: u32,
     pcss_blocker_search_samples: u32,
-    _padding2: [u32; 2],
+    constant_depth_bias: f32,
+    _padding2: u32,
 }
 
 /// A component that stores the ID of a shadow map in the shadow map atlas for the entities.

lyra-game/src/render/shaders/base.wgsl

@@ -123,6 +123,7 @@ struct LightShadowMapUniform {
     has_shadow_settings: u32,
     pcf_samples_num: u32,
     pcss_blocker_search_samples: u32,
+    constant_depth_bias: f32,
 }
 
 struct ShadowSettingsUniform {
@@ -277,8 +278,7 @@ fn calc_shadow_dir_light(world_pos: vec3<f32>, world_normal: vec3<f32>, light_di
     let xy_remapped = proj_coords.xy * 0.5 + 0.5;
     
     // use a bias to avoid shadow acne
-    let bias = 0.005;//max(0.05 * (1.0 - dot(normal, light_dir)), 0.005);  
+    let current_depth = proj_coords.z - map_data.constant_depth_bias;
-    let current_depth = proj_coords.z - bias;
 
     // get settings
     let settings = get_shadow_settings(map_data);
@@ -427,7 +427,7 @@ fn calc_shadow_point_light(world_pos: vec3<f32>, world_normal: vec3<f32>, light_
     
     var current_depth = length(frag_to_light);
     current_depth /= u.far_plane;
-    current_depth -= 0.005; // TODO: find a better way to calculate bias
+    current_depth -= u.constant_depth_bias;
 
     // get settings
     let settings = get_shadow_settings(u);

lyra-game/src/render/shaders/shadows.wgsl

@@ -19,6 +19,7 @@ struct LightShadowMapUniform {
     has_shadow_settings: u32,
     pcf_samples_num: u32,
     pcss_blocker_search_samples: u32,
+    constant_depth_bias: f32,
 }
 
 @group(0) @binding(0)