feat: Iterate over objects to find first hit

Closes #2

src/first_hit.cpp

@@ -8,9 +8,23 @@ bool first_hit(
     double & t,
     Eigen::Vector3d & n)
 {
-  ////////////////////////////////////////////////////////////////////////////
-  // Replace with your code here:
-  return false;
-  ////////////////////////////////////////////////////////////////////////////
+    bool hit = false;
+    t = -1;
+
+    double t_temp;
+    Eigen::Vector3d n_temp;
+
+    for (int i = 0; i < objects.size(); ++i) {
+        if (objects[i]->intersect(ray, min_t, t_temp, n_temp)) {
+            hit = true;
+            if (t == -1 || t_temp < t) {
+                hit_id = i;
+                t = t_temp;
+                n = n_temp;
+            }
+        }
+    }
+
+    return hit;
 }