Add a simple camera and antialiasing

camera.c

@@ -0,0 +1,23 @@
+#include "camera.h"
+
+void camera_init(Camera *camera, double aspect_ratio) {
+  double viewport_height = 2;
+  double viewport_width = aspect_ratio * viewport_height;
+  double focal_length = 1.0;
+
+  camera->origin = (Point3){0, 0, 0};
+  camera->horizontal = (Vec3){viewport_width, 0, 0};
+  camera->vertical = (Vec3){0, viewport_height, 0};
+  Vec3 offset =
+      vec3_add(vec3_div(camera->horizontal, 2), vec3_div(camera->vertical, 2));
+  offset = vec3_add(offset, (Vec3){0, 0, focal_length});
+  camera->lower_left_corner = point3_add(camera->origin, vec3_neg(offset));
+}
+
+Ray camera_get_ray(const Camera *camera, double u, double v) {
+  Point3 screen_point = point3_add(
+      camera->lower_left_corner,
+      vec3_add(vec3_mul(u, camera->horizontal), vec3_mul(v, camera->vertical)));
+  Vec3 direction = point3_sub(screen_point, camera->origin);
+  return (Ray){camera->origin, direction};
+}

camera.h

@@ -0,0 +1,19 @@
+#ifndef INCLUDED_CAMERA_H
+#define INCLUDED_CAMERA_H
+
+#include "point3.h"
+#include "ray.h"
+#include "vec3.h"
+
+typedef struct Camera {
+  Point3 origin;
+  Point3 lower_left_corner;
+  Vec3 horizontal;
+  Vec3 vertical;
+} Camera;
+
+void camera_init(Camera *camera, double aspect_ratio);
+
+Ray camera_get_ray(const Camera *camera, double u, double v);
+
+#endif /* INCLUDED_CAMERA_H */

color.c

@@ -1,6 +1,12 @@
 #include "color.h"
+#include "utils.h"
+
 #include <stdio.h>
 
+Color color_add(Color c1, Color c2) {
+  return (Color){c1.r + c2.r, c1.g + c2.g, c1.b + c2.b};
+}
+
 Color color_lerp(Color c1, Color c2, double t) {
   return (Color){
       (1.0 - t) * c1.r + t * c2.r,
@@ -9,7 +15,15 @@ Color color_lerp(Color c1, Color c2, double t) {
   };
 }
 
-void color_write(FILE *out, Color c) {
-  fprintf(out, "%d %d %d\n", (int)(255.999 * c.r), (int)(255.999 * c.g),
-          (int)(255.999 * c.b));
+void color_write(FILE *out, Color c, int samples_per_pixel) {
+  double scale = 1.0 / samples_per_pixel;
+  double r = c.r * scale;
+  double g = c.g * scale;
+  double b = c.b * scale;
+
+  int ir = (int)(256 * clamp(r, 0.0, 0.999));
+  int ig = (int)(256 * clamp(g, 0.0, 0.999));
+  int ib = (int)(256 * clamp(b, 0.0, 0.999));
+
+  fprintf(out, "%d %d %d\n", ir, ig, ib);
 }

color.h

@@ -7,8 +7,10 @@ typedef struct Color {
   double r, g, b;
 } Color;
 
+Color color_add(Color c1, Color c2);
+
 Color color_lerp(Color c1, Color c2, double t);
 
-void color_write(FILE *out, Color c);
+void color_write(FILE *out, Color c, int samples_per_pixel);
 
 #endif /* INCLUDED_COLOR_H */

main.c

@@ -3,10 +3,12 @@
 #include <stdbool.h>
 #include <stdio.h>
 
+#include "camera.h"
 #include "color.h"
 #include "hittable.h"
 #include "point3.h"
 #include "ray.h"
+#include "utils.h"
 #include "vec3.h"
 
 Color ray_color(Ray r, Hittable world) {
@@ -27,54 +29,48 @@ int main(void) {
   const double aspect_ratio = 16.0 / 9.0;
   const int image_width = 256;
   const int image_height = (int)(image_width / aspect_ratio);
+  const int samples_per_pixel = 100;
 
   /* World */
-  HittableList world = {0};
-  hittable_list_add(&world, make_hittable_sphere(&(Sphere){
+  HittableList object_list = {0};
+  hittable_list_add(&object_list, make_hittable_sphere(&(Sphere){
                                       .center = (Point3){0, 0, -1},
                                       .radius = 0.5,
                                   }));
-  hittable_list_add(&world, make_hittable_sphere(&(Sphere){
+  hittable_list_add(&object_list, make_hittable_sphere(&(Sphere){
                                       .center = (Point3){0, -100.5, -1},
                                       .radius = 100,
                                   }));
+  Hittable world = make_hittable_list(&object_list);
 
-  /* Camera parameters */
-  double viewport_height = 2;
-  double viewport_width = aspect_ratio * viewport_height;
-  double focal_length = 1.0;
-
-  Point3 origin = {0};
-  Vec3 horizontal = {viewport_width, 0, 0};
-  Vec3 vertical = {0, viewport_height, 0};
-  Vec3 offset = vec3_add(vec3_div(horizontal, 2), vec3_div(vertical, 2));
-  offset = vec3_add(offset, (Vec3){0, 0, focal_length});
-  Point3 lower_left_corner = point3_add(origin, vec3_neg(offset));
+  /* Camera */
+  Camera camera;
+  camera_init(&camera, aspect_ratio);
 
   printf("P3\n%u %u\n255\n", image_width, image_height);
 
   for (int j = image_height - 1; j >= 0; --j) {
     fprintf(stderr, "\rScanlines remaining: %d      ", j);
     for (int i = 0; i < image_width; ++i) {
-      double u = (double)i / (image_width - 1);
-      double v = (double)j / (image_height - 1);
-      Point3 screen_point =
-          point3_add(lower_left_corner,
-                     vec3_add(vec3_mul(u, horizontal), vec3_mul(v, vertical)));
-      Vec3 direction = point3_sub(screen_point, origin);
-      Ray r = {origin, direction};
-      Color pixel_color = ray_color(r, make_hittable_list(&world));
-      color_write(stdout, pixel_color);
+      Color pixel_color = {0, 0, 0};
+      for (int s = 0; s < samples_per_pixel; ++s) {
+        double u = (i + random_double()) / (image_width - 1);
+        double v = (j + random_double()) / (image_height - 1);
+        Ray r = camera_get_ray(&camera, u, v);
+        pixel_color = color_add(pixel_color, ray_color(r, world));
+      }
+      color_write(stdout, pixel_color, samples_per_pixel);
     }
   }
 
   fprintf(stderr, "\nDone.\n");
 
-  hittable_list_free(&world);
+  hittable_list_free(&object_list);
 
   return 0;
 }
 
+#include "camera.c"
 #include "color.c"
 #include "hittable.c"
 #include "point3.c"

utils.c

@@ -1,7 +1,20 @@
 #include "utils.h"
 
 #include <math.h>
+#include <stdlib.h>
 
-double degrees_to_radians(double degrees) {
-    return degrees * M_PI / 180.0;
+double degrees_to_radians(double degrees) { return degrees * M_PI / 180.0; }
+
+double random_double(void) { return rand() / (RAND_MAX + 1.0); }
+
+double random_double_in_range(double min, double max) {
+  return min + (max - min) * random_double();
+}
+
+double clamp(double x, double min, double max) {
+  if (x < min)
+    return min;
+  if (x > max)
+    return max;
+  return x;
 }

utils.h

@@ -3,4 +3,9 @@
 
 double degrees_to_radians(double degrees);
 
+double random_double(void);
+double random_double_in_range(double min, double max);
+
+double clamp(double x, double min, double max);
+
 #endif /* INCLUDED_UTILS_H */