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 {
@@ -183,7 +184,7 @@ fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
             let shadow_u: LightShadowMapUniform = u_light_shadow[light.light_shadow_uniform_index[0]];
             let frag_pos_light_space = shadow_u.light_space_matrix * vec4<f32>(in.world_position, 1.0);
 
-            let shadow = calc_shadow_dir_light(in.world_normal, light_dir, frag_pos_light_space, atlas_dimensions, shadow_u);
+            let shadow = calc_shadow_dir_light(in.world_position, in.world_normal, light_dir, light);
             light_res += blinn_phong_dir_light(in.world_position, in.world_normal, light, u_material, specular_color, shadow);
         } else if (light.light_ty == LIGHT_TY_POINT) {
             let shadow = calc_shadow_point_light(in.world_position, in.world_normal, light_dir, light, atlas_dimensions);
@@ -265,7 +266,10 @@ fn get_shadow_settings(shadow_u: LightShadowMapUniform) -> vec2<u32> {
     }
 }
 
-fn calc_shadow_dir_light(normal: vec3<f32>, light_dir: vec3<f32>, frag_pos_light_space: vec4<f32>, atlas_dimensions: vec2<i32>, shadow_u: LightShadowMapUniform) -> f32 {
+fn calc_shadow_dir_light(world_pos: vec3<f32>, world_normal: vec3<f32>, light_dir: vec3<f32>, light: Light) -> f32 {
+    let map_data: LightShadowMapUniform = u_light_shadow[light.light_shadow_uniform_index[0]];
+    let frag_pos_light_space = map_data.light_space_matrix * vec4<f32>(world_pos, 1.0);
+
     var proj_coords = frag_pos_light_space.xyz / frag_pos_light_space.w;
     // for some reason the y component is flipped after transforming
     proj_coords.y = -proj_coords.y;
@@ -274,32 +278,31 @@ fn calc_shadow_dir_light(normal: vec3<f32>, light_dir: vec3<f32>, frag_pos_light
     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 - bias;
+    let current_depth = proj_coords.z - map_data.constant_depth_bias;
 
     // get settings
-    let settings = get_shadow_settings(shadow_u);
+    let settings = get_shadow_settings(map_data);
     let pcf_samples_num = settings.x;
     let pcss_blocker_search_samples = settings.y;
 
     var shadow = 0.0;
     // hardware 2x2 PCF via camparison sampler
     if pcf_samples_num == 2u {
-        let region_coords = to_atlas_frame_coords(shadow_u, xy_remapped);
+        let region_coords = to_atlas_frame_coords(map_data, xy_remapped, false);
         shadow = textureSampleCompareLevel(t_shadow_maps_atlas, s_shadow_maps_atlas_compare, region_coords, current_depth);
     }
     // PCSS
     else if pcf_samples_num > 0u && pcss_blocker_search_samples > 0u {
-        shadow = pcss_dir_light(xy_remapped, current_depth, shadow_u);
+        shadow = pcss_dir_light(xy_remapped, current_depth, map_data);
     }
     // only PCF
     else if pcf_samples_num > 0u {
-        let texel_size = 1.0 / f32(shadow_u.atlas_frame.width);
-        shadow = pcf_dir_light(xy_remapped, current_depth, shadow_u, texel_size);
+        let texel_size = 1.0 / f32(map_data.atlas_frame.width);
+        shadow = pcf_dir_light(xy_remapped, current_depth, map_data, texel_size);
     }
     // no filtering
     else {
-        let region_coords = to_atlas_frame_coords(shadow_u, xy_remapped);
+        let region_coords = to_atlas_frame_coords(map_data, xy_remapped, false);
         let closest_depth = textureSampleLevel(t_shadow_maps_atlas, s_shadow_maps_atlas, region_coords, 0.0);
         shadow = select(1.0, 0.0, current_depth > closest_depth);
     }
@@ -323,7 +326,10 @@ fn search_width(light_near: f32, uv_light_size: f32, receiver_depth: f32) -> f32
 }
 
 /// Convert texture coords to be texture coords of an atlas frame.
-fn to_atlas_frame_coords(shadow_u: LightShadowMapUniform, coords: vec2<f32>) -> vec2<f32> {
+///
+/// If `safety_offset` is true, the frame will be shrank by a tiny amount to avoid bleeding
+/// into adjacent frames from fiiltering.
+fn to_atlas_frame_coords(shadow_u: LightShadowMapUniform, coords: vec2<f32>, safety_offset: bool) -> vec2<f32> {
     let atlas_dimensions = textureDimensions(t_shadow_maps_atlas);
     
     // get the rect of the frame as a vec4
@@ -332,9 +338,9 @@ fn to_atlas_frame_coords(shadow_u: LightShadowMapUniform, coords: vec2<f32>) ->
     // put the frame rect in atlas UV space
     region_rect /= f32(atlas_dimensions.x);
 
-    // calculate a relatively tiny offset to avoid getting the end of the frame and causing
-    // linear or nearest filtering to bleed to the adjacent frame.
-    let texel_size = (1.0 / f32(shadow_u.atlas_frame.x)) * 4.0;
+    // if safety_offset is true, calculate a relatively tiny offset to avoid getting the end of
+    // the frame and causing linear or nearest filtering to bleed to the adjacent frame.
+    let texel_size = select(0.0, (1.0 / f32(shadow_u.atlas_frame.x)) * 4.0, safety_offset);
     
     // lerp input coords 
     let region_coords = vec2<f32>(
@@ -354,7 +360,7 @@ fn find_blocker_distance_dir_light(tex_coords: vec2<f32>, receiver_depth: f32, b
     let samples = i32(u_shadow_settings.pcss_blocker_search_samples);
     for (var i = 0; i < samples; i++) {
         let offset_coords = tex_coords + u_pcss_poisson_disc[i] * search_width;
-        let new_coords = to_atlas_frame_coords(shadow_u, offset_coords);
+        let new_coords = to_atlas_frame_coords(shadow_u, offset_coords, false);
         let z = textureSampleLevel(t_shadow_maps_atlas, s_shadow_maps_atlas, new_coords, 0.0);
 
         if z < (receiver_depth - bias) {
@@ -390,7 +396,7 @@ fn pcf_dir_light(tex_coords: vec2<f32>, test_depth: f32, shadow_u: LightShadowMa
     let samples_num = i32(u_shadow_settings.pcf_samples_num);
     for (var i = 0; i < samples_num; i++) {
         let offset = tex_coords + u_pcf_poisson_disc[i] * uv_radius;
-        let new_coords = to_atlas_frame_coords(shadow_u, offset);
+        let new_coords = to_atlas_frame_coords(shadow_u, offset, false);
         
         shadow += textureSampleCompare(t_shadow_maps_atlas, s_shadow_maps_atlas_compare, new_coords, test_depth);
     }
@@ -421,7 +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);
@@ -431,7 +437,7 @@ fn calc_shadow_point_light(world_pos: vec3<f32>, world_normal: vec3<f32>, light_
     var shadow = 0.0;
     // hardware 2x2 PCF via camparison sampler
     if pcf_samples_num == 2u {
-        let region_coords = to_atlas_frame_coords(u, coords_2d);
+        let region_coords = to_atlas_frame_coords(u, coords_2d, true);
         shadow = textureSampleCompareLevel(t_shadow_maps_atlas, s_shadow_maps_atlas_compare, region_coords, current_depth);
     }
     // PCSS
@@ -446,7 +452,7 @@ fn calc_shadow_point_light(world_pos: vec3<f32>, world_normal: vec3<f32>, light_
     }
     // no filtering
     else {
-        let region_coords = to_atlas_frame_coords(u, coords_2d);
+        let region_coords = to_atlas_frame_coords(u, coords_2d, true);
         let closest_depth = textureSampleLevel(t_shadow_maps_atlas, s_shadow_maps_atlas, region_coords, 0.0);
         shadow = select(1.0, 0.0, current_depth > closest_depth);
     }
@@ -467,7 +473,7 @@ fn pcf_point_light(tex_coords: vec3<f32>, test_depth: f32, shadow_us: array<Ligh
 
         coords_2d += u_pcf_poisson_disc[i] * uv_radius;
 
-        let new_coords = to_atlas_frame_coords(shadow_u, coords_2d);
+        let new_coords = to_atlas_frame_coords(shadow_u, coords_2d, true);
         shadow += textureSampleCompare(t_shadow_maps_atlas, s_shadow_maps_atlas_compare, new_coords, test_depth);
     }
     shadow /= f32(samples_num);

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)