Hemispherical scattering

rtiww/src/main.cpp

@@ -15,7 +15,7 @@ color ray_color(const ray &r, const hittable &world, int depth) {
     return color(0, 0, 0);
 
   if (world.hit(r, 0.001, infinity, rec)) {
-    point3 target = rec.p + rec.normal + random_in_unit_sphere();
+    point3 target = rec.p + random_in_hemisphere(rec.normal);
     return 0.5 * ray_color(ray(rec.p, target - rec.p), world, depth - 1);
   }
 
@@ -58,7 +58,7 @@ int main() {
         pixel_color += ray_color(r, world, max_depth);
       }
 
-      p.set_pixel(j,i,pixel_color);
+      p.set_pixel(j, i, pixel_color);
     }
   }
 

rtiww/src/vec3.h

@@ -104,4 +104,15 @@ vec3 random_in_unit_sphere() {
   }
 }
 
+vec3 random_unit_vector() { return unit_vector(random_in_unit_sphere()); }
+
+vec3 random_in_hemisphere(const vec3 &normal) {
+  vec3 in_unit_sphere = random_in_unit_sphere();
+
+  if (dot(in_unit_sphere, normal) > 0.0) // In the same hemisphere as the normal
+    return in_unit_sphere;
+  else
+    return -in_unit_sphere;
+}
+
 #endif // RTIWW_VEC3_H