add camera + multisampling

src/camera.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include "rtweekend.h"
+
+class camera
+{
+    public:
+        const double ASPECT_RATIO = 16.0 / 9.0;
+        const double VIEWPORT_HEIGHT = 2.0;
+        const double VIEWPORT_WIDTH = ASPECT_RATIO * VIEWPORT_HEIGHT;
+        const double FOCAL_LENGTH = 1.0;
+
+        camera() : 
+            origin_(point3(0,0,0)),
+            horizontal_(vec3(VIEWPORT_WIDTH,0.0,0.0)),
+            vertical_(vec3(0.0, VIEWPORT_HEIGHT, 0.0))
+        {
+            lower_left_corner_ = origin_ - horizontal_/2 - vertical_/2 - vec3(0,0,FOCAL_LENGTH);
+        }
+
+        ray get_ray(double u, double v) const 
+        {
+            return ray(origin_, lower_left_corner_ + u*horizontal_ + v*vertical_ - origin_);
+        }
+
+    private:
+        point3  origin_;
+        point3  lower_left_corner_;
+        vec3    horizontal_;
+        vec3    vertical_;
+};

src/colour.h

@@ -1,13 +1,23 @@
 #pragma once
 
-#include "vec3.h"
+#include "rtweekend.h"
 
 #include <iostream>
 
-void write_colour(std::ostream &out, colour pixel_colour)
+void write_colour(std::ostream &out, colour pixel_colour, int samples_per_pixel)
 {
+    auto r = pixel_colour.x();
+    auto g = pixel_colour.y();
+    auto b = pixel_colour.z();
+
+    // divide the colour total by the number of samples
+    auto scale = 1.0 / samples_per_pixel;
+    r *= scale;
+    g *= scale;
+    b *= scale;
+    
     // write the translated [0,255] value of each colour component.
-    out << static_cast<int>(255.999 * pixel_colour.x()) << ' '
-        << static_cast<int>(255.999 * pixel_colour.y()) << ' '
-        << static_cast<int>(255.999 * pixel_colour.z()) << '\n';
+    out << static_cast<int>(256 * clamp(r, 0.0, 0.999)) << ' '
+        << static_cast<int>(256 * clamp(g, 0.0, 0.999)) << ' '
+        << static_cast<int>(256 * clamp(b, 0.0, 0.999)) << '\n';
 }

src/main.cpp

@@ -3,12 +3,14 @@
 #include "hittable_list.h"
 #include "sphere.h"
 #include "colour.h"
+#include "camera.h"
 
 #include <iostream>
 
 const double ASPECT_RATIO = 16.0 / 9.0;
 const int WIDTH = 384;
 const int HEIGHT = static_cast<int>(WIDTH / ASPECT_RATIO);
+const int SAMPLES_PER_PIXEL = 100;
 
 colour ray_colour(const ray& r, const hittable& world)
 {
@@ -44,17 +46,24 @@ int main()
     world.add(make_shared<sphere>(point3(0,0,-1), 0.5));
     world.add(make_shared<sphere>(point3(0,-100.5,-1), 100));
 
-    for (int y = HEIGHT - 1; y >= 0; --y)
+    camera cam;
+
+    for (int j = HEIGHT - 1; j >= 0; --j)
     {
-        std::cerr << "\rScanlines remaining: " << y << ' ' << std::flush;
-        for (int x = 0; x < WIDTH; ++x)
+        std::cerr << "\rScanlines remaining: " << j << ' ' << std::flush;
+        for (int i = 0; i < WIDTH; ++i)
         {
-            auto u = double(x) / (WIDTH-1);
-            auto v = double(y) / (HEIGHT-1);
-            ray r(origin, lower_left_corner + u*horizontal + v*vertical - origin);
-            
-            colour pixel_colour = ray_colour(r, world);
-            write_colour(std::cout, pixel_colour);
+            colour pixel_colour(0,0,0);
+
+            for (int s = 0; s < SAMPLES_PER_PIXEL; ++s)
+            {
+                auto u = (i + random_double()) / (WIDTH-1);
+                auto v = (j + random_double()) / (HEIGHT-1);
+                ray r = cam.get_ray(u, v);
+                pixel_colour += ray_colour(r, world);
+            }
+
+            write_colour(std::cout, pixel_colour, SAMPLES_PER_PIXEL);
         }
     }
 

src/rtweekend.h

@@ -23,6 +23,25 @@ inline double degrees_to_radians(double degrees)
     return degrees * pi / 180;
 }
 
+inline double random_double()
+{
+    // returns a random real in [0,1)
+    return rand() / (RAND_MAX + 1.0);
+}
+
+inline double random_double(double min, double max)
+{
+    // returns a random real in [min,max)
+    return min + (max-min)*random_double();
+}
+
+inline double clamp(double x, double min, double max)
+{
+    if (x < min) return min;
+    if (x > max) return max;
+    return x;
+}
+
 // common headers
 
 #include "ray.h"