add different diffuse renderer

src/main.rs

@@ -27,7 +27,7 @@ fn ray_color(r: &Ray, world: &HittableList, depth: u32) -> Color {
     }
 
     if world.hit(r, 0.0, f64::INFINITY, &mut rec) {
-        let target = rec.p + rec.normal + Vec3::random_in_unit_sphere();
+        let target = rec.p + rec.normal + Vec3::random_unit_vector(); // rec.p + rec.normal.random_in_hemisphere();
         return 0.5 * ray_color(&Ray::new(rec.p, target - rec.p), world, depth-1);
     }
     let unit_direction = r.direction();
@@ -43,7 +43,7 @@ fn main() {
     let aspect_ratio = 16.0 / 9.0;
     let image_width = 1000;
     let image_height = (image_width as f64 / aspect_ratio) as u32;
-    let samples_per_pixel = 10_u32;
+    let samples_per_pixel = 50_u32;
     let max_depth = 50;
 
     // World

src/vec3.rs

@@ -54,6 +54,19 @@ impl Vec3 {
         }
     }
 
+    pub fn random_unit_vector() -> Self {
+        Self::unit_vector(Self::random_in_unit_sphere())
+    }
+
+    pub fn random_in_hemisphere(&self) -> Self {
+        let in_unit_sphere = Self::random_in_unit_sphere();
+        if Self::dot(in_unit_sphere, *self) > 0.0 {
+            return in_unit_sphere;
+        } else {
+            return -1.0*in_unit_sphere;
+        }
+    }
+
     pub fn x(&self) -> f64 {
         self.e[0]
     }