From 73473e772058c223deb0e8a70be3abd84fa0a9a4 Mon Sep 17 00:00:00 2001
From: Keuin <keuinx@gmail.com>
Date: Tue, 12 Apr 2022 13:54:52 +0800
Subject: Bugfix: object hit priority is incorrect. Replace unique_ptr with
 shared_ptr.

---
 main_simple_scanner.cpp | 34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/main_simple_scanner.cpp b/main_simple_scanner.cpp
index 51870eb..13154e5 100644
--- a/main_simple_scanner.cpp
+++ b/main_simple_scanner.cpp
@@ -98,21 +98,31 @@ public:
 class viewport {
     double half_width, half_height; // viewport size
     vec3d center; // coordinate of the viewport center point
-    std::vector<std::unique_ptr<object>> objects;
+    std::vector<std::shared_ptr<object>> objects; // TODO move to world class
 
     // Given a ray from the camera, generate a color the camera seen on the viewport.
     pixel8b color(const ray3d &r) {
         // Detect hits
-        double hit_t;
+        bool hit = false;
+        double hit_t = std::numeric_limits<double>::infinity();
+        std::shared_ptr<object> hit_obj;
+        // Check the nearest object we hit
         for (const auto &obj: objects) {
-            if (obj->hit(r, hit_t, 0.0)) {
-                // normal vector on hit point
-                const auto nv = obj->normal_vector(r.at(hit_t));
-//                return obj->color();
-                // visualize normal vector at hit point
-                return pixel8b::from_normalized(nv);
+            double t_;
+            if (obj->hit(r, t_, 0.0) && t_ < hit_t) {
+                hit = true;
+                hit_t = t_;
+                hit_obj = obj;
             }
         }
+        if (hit) {
+            // normal vector on hit point
+            const auto nv = hit_obj->normal_vector(r.at(hit_t));
+//                return obj->color();
+            // visualize normal vector at hit point
+            return pixel8b::from_normalized(nv);
+        }
+
 
         // Does not hit anything. Get background color (infinity)
         const auto u = (r.direction().y + 1.0) * 0.5;
@@ -131,7 +141,7 @@ public:
             half_width(width / 2.0), half_height(height / 2.0), center(viewport_center) {}
 
     // Add an object to the world.
-    void add_object(std::unique_ptr<object> &&obj) {
+    void add_object(std::shared_ptr<object> &&obj) {
         objects.push_back(std::move(obj));
     }
 
@@ -162,10 +172,10 @@ void generate_image(uint16_t image_width, uint16_t image_height, double viewport
                     double sphere_z, double sphere_r) {
     double r = 1.0 * image_width / image_height;
     viewport vp{viewport_width, viewport_width / r, vec3d{0, 0, -focal_length}};
-    vp.add_object(std::unique_ptr<object>{new sphere{
+    vp.add_object(std::make_shared<sphere>(
             vec3d{0, -100.5, -1},
-            100}}); // the earth
-    vp.add_object(std::unique_ptr<object>{new sphere{vec3d{0, 0, sphere_z}, sphere_r}});
+            100)); // the earth
+    vp.add_object(std::make_shared<sphere>(vec3d{0, 0, sphere_z}, sphere_r));
     timer tm;
     tm.start_measure();
     const auto image = vp.render(vec3d::zero(), image_width, image_height); // camera position as the coordinate origin
-- 
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