Make world ref const in ray_color() function

Author: hollasch

books/RayTracingInOneWeekend.html

@@ -1073,7 +1073,7 @@
     #include <iostream>
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
-    vec3 ray_color(const ray& r, hittable& world) {
+    vec3 ray_color(const ray& r, const hittable& world) {
         hit_record rec;
         if (world.hit(r, 0.0, infinity, rec)) {
             return 0.5 * (rec.normal + vec3(1,1,1));
@@ -1395,7 +1395,7 @@
 Then update the `ray_color()` function to use the new random direction generator:
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
-    vec3 ray_color(const ray& r, hittable& world) {
+    vec3 ray_color(const ray& r, const hittable& world) {
         hit_record rec;
         if (world.hit(r, 0.0, infinity, rec)) {
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
@@ -1419,7 +1419,7 @@
 depth, returning no light contribution at the maximum depth:
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
-    vec3 ray_color(const ray& r, hittable& world, int depth) {
+    vec3 ray_color(const ray& r, const hittable& world, int depth) {
         hit_record rec;
         if (world.hit(r, 0.0, infinity, rec)) {
             // If we've exceeded the ray bounce limit, no more light is gathered.
@@ -1558,7 +1558,7 @@
 function.
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
-    vec3 ray_color(const ray& r, hittable& world, int depth) {
+    vec3 ray_color(const ray& r, const hittable& world, int depth) {
         hit_record rec;
         if (world.hit(r, 0.0, infinity, rec)) {
             // If we've exceeded the ray bounce limit, no more light is gathered.
@@ -1634,7 +1634,7 @@
 Plugging the new formula into the `ray_color()` function:
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
-    vec3 ray_color(const ray& r, hittable& world, int depth) {
+    vec3 ray_color(const ray& r, const hittable& world, int depth) {
         hit_record rec;
         if (world.hit(r, 0.0, infinity, rec)) {
             // If we've exceeded the ray bounce limit, no more light is gathered.
@@ -1879,7 +1879,7 @@
 We need to modify the color function to use this:
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
-    vec3 ray_color(const ray& r, hittable& world, int depth) {
+    vec3 ray_color(const ray& r, const hittable& world, int depth) {
         hit_record rec;
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
         if (world.hit(r, 0.001, infinity, rec)) {

books/RayTracingTheNextWeek.html

@@ -1741,7 +1741,7 @@
 the new `emitted` value.
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
-    vec3 ray_color(const ray& r, const vec3& background, hittable& world, int depth) {
+    vec3 ray_color(const ray& r, const vec3& background, const hittable& world, int depth) {
         hit_record rec;
 
         // If we've exceeded the ray bounce limit, no more light is gathered.

books/RayTracingTheRestOfYourLife.html

@@ -842,7 +842,7 @@
 And the color function gets a minor modification:
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
-    vec3 ray_color(const ray& r, const vec3& background, hittable& world, int depth) {
+    vec3 ray_color(const ray& r, const vec3& background, const hittable& world, int depth) {
         hit_record rec;
 
         // If we've exceeded the ray bounce limit, no more light is gathered.
@@ -1304,7 +1304,7 @@
 that math and get the concept, we can add it (see the highlighted region):
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
-    vec3 ray_color(const ray& r, const vec3& background, hittable& world, int depth) {
+    vec3 ray_color(const ray& r, const vec3& background, const hittable& world, int depth) {
         hit_record rec;
 
         // If we've exceeded the ray bounce limit, no more light is gathered.
@@ -1486,7 +1486,7 @@
 change variable `pdf` to some other variable name to avoid a name conflict with the new `pdf` class.
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
-    vec3 ray_color(const ray& r, const vec3& background, hittable& world, int depth) {
+    vec3 ray_color(const ray& r, const vec3& background, const hittable& world, int depth) {
         hit_record rec;
 
         // If we've exceeded the ray bounce limit, no more light is gathered.
@@ -1627,7 +1627,7 @@
 And then change `ray_color()`:
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
-    vec3 ray_color(const ray& r, const vec3& background, hittable& world, int depth) {
+    vec3 ray_color(const ray& r, const vec3& background, const hittable& world, int depth) {
         hit_record rec;
 
         // If we've exceeded the ray bounce limit, no more light is gathered.
@@ -1708,7 +1708,7 @@
     vec3 ray_color(
         const ray& r,
         const vec3& background,
-        hittable& world,
+        const hittable& world,
         shared_ptr<hittable> lights,
         int depth
     ) {
@@ -1908,7 +1908,7 @@
     vec3 ray_color(
         const ray& r,
         const vec3& background,
-        hittable& world,
+        const hittable& world,
         shared_ptr<hittable> lights,
         int depth
     ) {
@@ -1984,7 +1984,7 @@
     vec3 ray_color(
         const ray& r,
         const vec3& background,
-        hittable& world,
+        const hittable& world,
         shared_ptr<hittable> lights,
         int depth
     ) {

src/InOneWeekend/main.cc

@@ -17,7 +17,7 @@
 #include <iostream>
 
 
-vec3 ray_color(const ray& r, hittable& world, int depth) {
+vec3 ray_color(const ray& r, const hittable& world, int depth) {
     hit_record rec;
 
     // If we've exceeded the ray bounce limit, no more light is gathered.

src/TheNextWeek/main.cc

@@ -23,7 +23,7 @@
 #include <iostream>
 
 
-vec3 ray_color(const ray& r, const vec3& background, hittable& world, int depth) {
+vec3 ray_color(const ray& r, const vec3& background, const hittable& world, int depth) {
     hit_record rec;
 
     // If we've exceeded the ray bounce limit, no more light is gathered.

src/TheRestOfYourLife/main.cc

@@ -22,7 +22,7 @@
 vec3 ray_color(
     const ray& r,
     const vec3& background,
-    hittable& world,
+    const hittable& world,
     shared_ptr<hittable> lights,
     int depth
 ) {