Improve Perlin class initialization

The prior form defined a private `init()` method to initialize the
Perlin class. This had several drawbacks. First, there really wasn't a
need for the indirection of calling a separate method from the
constructor. Second, because the `init()` method did not delete any
existing allocations, it was not safe to call more than once.

Given all this, there was really no good reason to not just perform the
initialization in the constructor.

Author: hollasch

books/RayTracingTheNextWeek.html

@@ -1060,7 +1060,14 @@
     class perlin {
         public:
             perlin() {
-                init();
+                ranfloat = new double[point_count];
+                for (int i = 0; i < point_count; ++i) {
+                    ranfloat[i] = random_double();
+                }
+
+                perm_x = perlin_generate_perm();
+                perm_y = perlin_generate_perm();
+                perm_z = perlin_generate_perm();
             }
 
             ~perlin() {
@@ -1087,17 +1094,6 @@
             int* perm_y;
             int* perm_z;
 
-            void init() {
-                ranfloat = new double[point_count];
-                for (int i = 0; i < point_count; ++i) {
-                    ranfloat[i] = random_double();
-                }
-
-                perm_x = perlin_generate_perm();
-                perm_y = perlin_generate_perm();
-                perm_z = perlin_generate_perm();
-            }
-
             static int* perlin_generate_perm() {
                 auto p = new int[point_count];
 
@@ -1300,12 +1296,24 @@
 This is still a bit grid blocky looking, probably because the min and max of the pattern always
 lands exactly on the integer x/y/z. Ken Perlin’s very clever trick was to instead put random unit
 vectors (instead of just floats) on the lattice points, and use a dot product to move the min and
-max off the lattice. So, first we need to change the random floats to random vectors:
+max off the lattice. So, first we need to change the random floats to random vectors. These vectors
+are any reasonable set of irregular directions, and I won't bother to make them exactly uniform:
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
     class perlin {
         public:
-            ...
+            perlin() {
+                ranvec = new vec3[point_count];
+
+                for (int i = 0; i < point_count; ++i) {
+                    ranvec[i] = unit_vector(vec3::random(-1,1));
+                }
+
+                perm_x = perlin_generate_perm();
+                perm_y = perlin_generate_perm();
+                perm_z = perlin_generate_perm();
+            }
+
             ~perlin() {
                 delete[] ranvec;
                 delete[] perm_x;
@@ -1325,33 +1333,7 @@
 </div>
 
 <div class='together'>
-These vectors are any reasonable set of irregular directions, and I won't bother to make them
-exactly uniform:
-
-    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
-    class perlin {
-        ...
-        private:
-            ...
-            void init() {
-                ranvec = new vec3[point_count];
-
-                for (int i = 0; i < point_count; ++i) {
-                    ranvec[i] = unit_vector(vec3::random(-1,1));
-                }
-
-                perm_x = perlin_generate_perm();
-                perm_y = perlin_generate_perm();
-                perm_z = perlin_generate_perm();
-            }
-            ...
-    }
-    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-    [Listing [perlin-gen-2]: <kbd>[perlin.h]</kbd> New perlin_generate()]
-</div>
-
-<div class='together'>
-The Perlin class is now:
+The Perlin class `noise()` method is now:
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
     class perlin {
@@ -1380,7 +1362,7 @@
             ...
         }
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-    [Listing [perlin-2]: <kbd>[perlin.h]</kbd> The perlin class so far]
+    [Listing [perlin-2]: <kbd>[perlin.h]</kbd> Perlin class with new noise() method]
 </div>
 
 <div class='together'>

src/common/perlin.h

@@ -18,7 +18,14 @@
 class perlin {
     public:
         perlin() {
-            init();
+            ranvec = new vec3[point_count];
+            for (int i = 0; i < point_count; ++i) {
+                ranvec[i] = unit_vector(vec3::random(-1,1));
+            }
+
+            perm_x = perlin_generate_perm();
+            perm_y = perlin_generate_perm();
+            perm_z = perlin_generate_perm();
         }
 
         ~perlin() {
@@ -70,17 +77,6 @@ class perlin {
         int* perm_y;
         int* perm_z;
 
-        void init() {
-            ranvec = new vec3[point_count];
-            for (int i = 0; i < point_count; ++i) {
-                ranvec[i] = unit_vector(vec3::random(-1,1));
-            }
-
-            perm_x = perlin_generate_perm();
-            perm_y = perlin_generate_perm();
-            perm_z = perlin_generate_perm();
-        }
-
         static int* perlin_generate_perm() {
             auto p = new int[point_count];