add metal fuzziness

in_one_weekend/src/main.zig

@@ -93,22 +93,24 @@ pub fn main() anyerror!void {
     // World
     const materialGround = Material{
         .lambertian = material.Lambertian{
-            .color = Color{ .x = 0.8, .y = 0.8, .z = 0.0 }
+            .color = Color{ .x = 0.8, .y = 0.8, .z = 0.0 },
         }
     };
     const materialCenter = Material{
         .lambertian = material.Lambertian{
-            .color = Color{ .x = 0.7, .y = 0.3, .z = 0.3 }
+            .color = Color{ .x = 0.7, .y = 0.3, .z = 0.3 },
         }
     };
     const materialLeft = Material{
         .metal = material.Metal{
-            .color = Color{ .x = 0.8, .y = 0.8, .z = 0.8 }
+            .color = Color{ .x = 0.8, .y = 0.8, .z = 0.8 },
+            .fuzz = 0.3,
         }
     };
     const materialRight = Material{
         .metal = material.Metal{
-            .color = Color{ .x = 0.8, .y = 0.6, .z = 0.2 }
+            .color = Color{ .x = 0.8, .y = 0.6, .z = 0.2 },
+            .fuzz = 1.0,
         }
     };
 

in_one_weekend/src/material.zig

@@ -29,11 +29,11 @@ pub const Lambertian = struct {
 
 pub const Metal = struct {
     color: Color,
-    // fuzzy: f32,
+    fuzz: f32,
 
     pub fn scatter(self: Metal, ray: Ray, hit: HitRecord, rng: *Random) ?ScatteredRay {
         const reflected = ray.direction.unit().reflect(hit.normal);
-        const scattered = Ray{ .origin = hit.p, .direction = reflected };
+        const scattered = Ray{ .origin = hit.p, .direction = reflected.add(vec3.random_in_unit_sphere(rng).mul_s(self.fuzz)) };
         if (scattered.direction.dot(hit.normal) <= 0) {
             return null;
         }