Simplify lambertian scatter direction calculation

Resolves #340

Author: hollasch

books/RayTracingInOneWeekend.html

@@ -1813,8 +1813,8 @@
             virtual bool scatter(
                 const ray& r_in, const hit_record& rec, vec3& attenuation, ray& scattered
             ) const {
-                vec3 target = rec.p + rec.normal + random_unit_vector();
-                scattered = ray(rec.p, target-rec.p);
+                vec3 scatter_direction = rec.normal + random_unit_vector();
+                scattered = ray(rec.p, scatter_direction);
                 attenuation = albedo;
                 return true;
             }

books/RayTracingTheNextWeek.html

@@ -251,9 +251,9 @@
             virtual bool scatter(
                 const ray& r_in, const hit_record& rec, vec3& attenuation, ray& scattered
             ) const {
-                vec3 target = rec.p + rec.normal + random_unit_vector();
+                vec3 scatter_direction = rec.normal + random_unit_vector();
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
-                scattered = ray(rec.p, target-rec.p, r_in.time());
+                scattered = ray(rec.p, scatter_direction, r_in.time());
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
                 attenuation = albedo;
                 return true;
@@ -911,8 +911,8 @@
             virtual bool scatter(
                 const ray& r_in, const hit_record& rec, vec3& attenuation, ray& scattered
             ) const {
-                vec3 target = rec.p + rec.normal + random_unit_vector();
-                scattered = ray(rec.p, target - rec.p);
+                vec3 scatter_direction = rec.normal + random_unit_vector();
+                scattered = ray(rec.p, scatter_direction, r_in.time());
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
                 attenuation = albedo->value(rec.u, rec.v, rec.p);
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
@@ -2459,7 +2459,7 @@
             virtual bool scatter(
                 const ray& r_in, const hit_record& rec, vec3& attenuation, ray& scattered
             ) const  {
-                scattered = ray(rec.p, random_in_unit_sphere());
+                scattered = ray(rec.p, random_in_unit_sphere(), r_in.time());
                 attenuation = albedo->value(rec.u, rec.v, rec.p);
                 return true;
             }

src/InOneWeekend/material.h

@@ -76,10 +76,10 @@ class lambertian : public material {
         virtual bool scatter(
             const ray& r_in, const hit_record& rec, vec3& attenuation, ray& scattered
         ) const  {
-             vec3 target = rec.p + rec.normal + random_unit_vector();
-             scattered = ray(rec.p, target-rec.p);
-             attenuation = albedo;
-             return true;
+            vec3 scatter_direction = rec.normal + random_unit_vector();
+            scattered = ray(rec.p, scatter_direction);
+            attenuation = albedo;
+            return true;
         }
 
     public:

src/TheNextWeek/material.h

@@ -115,8 +115,8 @@ class lambertian : public material {
         virtual bool scatter(
             const ray& r_in, const hit_record& rec, vec3& attenuation, ray& scattered
         ) const {
-            vec3 target = rec.p + rec.normal + random_unit_vector();
-            scattered = ray(rec.p, target-rec.p, r_in.time());
+            vec3 scatter_direction = rec.normal + random_unit_vector();
+            scattered = ray(rec.p, scatter_direction, r_in.time());
             attenuation = albedo->value(rec.u, rec.v, rec.p);
             return true;
         }