Refactor: rename constant_texture::color

Member variable renamed from `color` to `solid_color`.

Author: hollasch

books/RayTracingTheNextWeek.html

@@ -889,14 +889,14 @@
     class constant_texture : public texture {
         public:
             constant_texture() {}
-            constant_texture(vec3 c) : color(c) {}
+            constant_texture(vec3 c) : solid_color(c) {}
 
             virtual vec3 value(double u, double v, const vec3& p) const {
-                return color;
+                return solid_color;
             }
 
         public:
-            vec3 color;
+            vec3 solid_color;
     };
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     [Listing [texture]: <kbd>[texture.h]</kbd> A texture class]

src/common/texture.h

@@ -25,14 +25,14 @@ class texture  {
 class constant_texture : public texture {
     public:
         constant_texture() {}
-        constant_texture(vec3 c) : color(c) {}
+        constant_texture(vec3 c) : solid_color(c) {}
 
         virtual vec3 value(double u, double v, const vec3& p) const {
-            return color;
+            return solid_color;
         }
 
     public:
-        vec3 color;
+        vec3 solid_color;
 };