dof

lib/src/shaders/standard_shader.wgsl

@@ -8,7 +8,7 @@
 //!
 //! ## Uniform Contract
 //! Four bind groups, shared by every material (one single pipeline layout — voir Étape 3) :
-//! - `@group(0) @binding(0)` : `FrameUniforms` (per-frame, camera + lights + shadow)   [784 bytes]
+//! - `@group(0) @binding(0)` : `FrameUniforms` (per-frame, camera + lights + shadow + fog)   [816 bytes]
 //! - `@group(1) @binding(0)` : `ObjectUniform` (per-entity model matrix)      [64 bytes]
 //! - `@group(2) @binding(0)` : `texture_sampler` (sampler) — diffuse        (Étape 10)
 //! - `@group(2) @binding(1)` : `diffuse_texture` (texture_2d<f32>)          (Étape 10)
@@ -93,6 +93,8 @@ struct FrameUniforms {
     light_view_proj: mat4x4<f32>,                // world → shadow light clip space (Étape 14, D3)
     shadow_params: vec4<f32>,                    // .x = map size, .y = constant bias, .z = slope bias
     options: vec4<u32>,                          // .x = unlit flag ; .y = shadows on
+    fog_a: vec4<f32>,                            // .x=enabled .y=mode .z=near .w=far (Étape 25)
+    fog_b: vec4<f32>,                            // .x=density .y/.z/.w=fog color RGB (Étape 25)
 };
 
 struct ObjectUniform {
@@ -151,7 +153,8 @@ fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
     // Flat (unlit) mode : pas d'éclairage, texel * couleur du vertex + emissive.
     if (frame.options.x != 0u) {
         let emissive_contrib = base * object.emissive.rgb * object.emissive.a;
-        return vec4<f32>(base + emissive_contrib, in.color.a);
+        let final_rgb = base + emissive_contrib;
+        return vec4<f32>(apply_fog(final_rgb, in.world_pos), in.color.a);
     }
 
     let n = normalize(in.normal);
@@ -208,7 +211,32 @@ fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
     // Étape 22 (6.2): emissive — added to the lit result (independent of lights/shadows).
     // Zero emissive (default) → no change (non-regression). In HDR, intensity > 1.0 glows.
     let emissive_contrib = base * object.emissive.rgb * object.emissive.a;
-    return vec4<f32>(lit + emissive_contrib, in.color.a);
+    let final_rgb = lit + emissive_contrib;
+    return vec4<f32>(apply_fog(final_rgb, in.world_pos), in.color.a);
+}
+
+// Étape 25 : distance fog. Blends the final color toward the fog color based on the
+// fragment's distance from the camera. Three modes: linear, exponential, exponential².
+// When `fog_a.x == 0` (disabled), returns the input color unchanged — zero cost.
+fn apply_fog(color: vec3<f32>, world_pos: vec3<f32>) -> vec3<f32> {
+    if (frame.fog_a.x < 0.5) {
+        return color;
+    }
+    let dist = length(world_pos - frame.cam_pos.xyz);
+    var fog_factor: f32;
+    if (frame.fog_a.y < 0.5) {
+        // Linear: 1.0 at near, 0.0 at far.
+        fog_factor = saturate((frame.fog_a.w - dist) / max(frame.fog_a.w - frame.fog_a.z, 1e-4));
+    } else if (frame.fog_a.y < 1.5) {
+        // Exponential: exp(-density * distance).
+        fog_factor = exp(-frame.fog_b.x * dist);
+    } else {
+        // Exponential²: exp(-density² * distance²) — sharper cutoff.
+        let d2 = frame.fog_b.x * frame.fog_b.x;
+        fog_factor = exp(-d2 * dist * dist);
+    }
+    let fog_color = frame.fog_b.yzw;
+    return mix(color, fog_color, 1.0 - fog_factor);
 }
 
 // Étape 14 (DRAFT 3.2, D5) : PCF shadow factor for this fragment. Reprojects the world position