1 files changed, 34 insertions, 11 deletions

diff --git a/src/main.cpp b/src/main.cpp
index b964aeb..e2ef071 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4,42 +4,63 @@
 #include "vec3.hpp"
 #include "ray.hpp"
 
+color ground_color { 1.0, 1.0, 1.0 };
+color sky_color { 0.5, 0.7, 1.0 };
+
+bool hit_sphere(const point3& sphere_pos, double sphere_radius, const ray& r) {
+    // Vector from the ray origin to sphere position
+    vec3 origin_center = r.origin - sphere_pos;
+    double a = r.direction.dot(r.direction);
+    double b = 2.0 * r.direction.dot(origin_center);
+    double c = origin_center.dot(origin_center) - sphere_radius * sphere_radius;
+    double discriminant = b * b - 4.0 * a * c;
+
+    return (discriminant > 0);
+}
+
 color ray_color(ray& r) {
     auto unit_dir = r.direction.unit();
     auto t = (unit_dir.y + 1.0) * 0.5;
 
-    return lerp(color(1.0, 1.0, 1.0), color(0.5, 0.7, 1.0), t);
+    auto c = lerp(ground_color, sky_color, t);
+
+    if (hit_sphere(point3{ 0.0, 0.0, -1.0 }, .5, r)) {
+        c = color { 1.0, 0.0, 0.0 };
+    }
+
+    return c;
 }
 
 int main() {
     // Image dimensions
+    const double aspect_ratio = 16.0 / 9.0;
     const size_t width = 400;
-    const size_t height = width / (16.0 / 9.0);
+    const size_t height = width / aspect_ratio;
     // const size_t width = 256;
     // const size_t height = 256;
 
-    const double aspect_ratio = width / height;
+    // const double aspect_ratio = width / height;
 
     // Viewport dimensions
-    const double viewport_width = 2.0;
-    const double viewport_height = viewport_width / aspect_ratio;
+    const double viewport_height = 2.0;
+    const double viewport_width = viewport_height * aspect_ratio;
 
     // Unit vectors for viewport pixels
     const vec3 horizontal { viewport_width / width, 0.0, 0.0 };
     const vec3 vertical { 0.0, viewport_height / height, 0.0 };
-    std::cerr << "Horizontal : " << horizontal << std::endl;
-    std::cerr << "Vertical : " << vertical << std::endl;
 
     // We use a right handed coord system
     const point3 eye_pos {};
     const double focal_length = 1.0;
 
-    const point3 viewport_first_pixel =
-        horizontal * -(viewport_width / 2.0) +
-        vertical * -(viewport_height / 2.0) +
-        point3{ 0.0, 0.0, -focal_length };
+    const point3 viewport_first_pixel {
+        -viewport_width / 2.0,
+        -viewport_height / 2.0,
+        -focal_length
+    };
 
     const point3 first_pixel = eye_pos + viewport_first_pixel;
+    std::cerr << viewport_first_pixel << std::endl;
 
     // PPM format header
     std::cout << "P3\n" << width << '\n' << height << "\n 255" << std::endl;
@@ -58,6 +79,8 @@ int main() {
             ray ray { eye_pos, direction };
 
             write_color(std::cout, ray_color(ray));
+            // write_color(std::cout, color(direction.unit().y, direction.unit().y, direction.unit().y));
+            // write_color(std::cout, color(y.y, y.y, y.y));
         }
     }