From 494b48c56017a28fb817eb639a85e542f5a9e710 Mon Sep 17 00:00:00 2001
From: Faerbit <faerbit@gmail.com>
Date: Sat, 6 Jun 2020 14:47:39 +0200
Subject: [PATCH] Implemented diffuse reflection.

---
 vec3.h      | 18 ++++++++++++++++++
 wtracer.cpp | 22 ++++++++++++++--------
 2 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/vec3.h b/vec3.h
index 04690c7..df7f98b 100644
--- a/vec3.h
+++ b/vec3.h
@@ -4,6 +4,8 @@
 #include <cmath>
 #include <iostream>
 
+#include "util.h"
+
 class Vec3 {
    public:
     Vec3() : e{0, 0, 0} {}
@@ -38,6 +40,14 @@ class Vec3 {
         return e[0] * e[0] + e[1] * e[1] + e[2] * e[2];
     }
 
+    inline static Vec3 random() {
+        return Vec3(random_double(), random_double(), random_double());
+    }
+
+    inline static Vec3 random(double min, double max) {
+        return Vec3(random_double(min, max), random_double(min, max), random_double(min, max));
+    }
+
    private:
     double e[3];
     
@@ -102,4 +112,12 @@ inline Vec3 unit_vector(Vec3 v) {
     return v / v.length();
 }
 
+Vec3 random_in_unit_sphere() {
+    while (true) {
+        auto p = Vec3::random(-1, 1);
+        if (p.length_squared() >= 1) continue;
+        return p;
+    }
+}
+
 #endif  // VEC3_H
diff --git a/wtracer.cpp b/wtracer.cpp
index 96b18d5..cf70ca0 100644
--- a/wtracer.cpp
+++ b/wtracer.cpp
@@ -9,10 +9,15 @@
 #include "sphere.h"
 #include "camera.h"
 
-Color ray_color(const Ray& r, const Hittable& world) {
+Color ray_color(const Ray& r, const Hittable& world, int depth) {
     hit_record rec;
+
+    if (depth <= 0)
+        return Color(0, 0, 0);
+
     if (world.hit(r, 0, infinity, rec)) {
-        return 0.5 * (rec.normal + Color(1,1,1));
+        Point3 target = rec.p + rec.normal + random_in_unit_sphere();
+        return 0.5 * ray_color(Ray(rec.p, target - rec.p), world, depth-1);
     }
     Vec3 unit_direction = unit_vector(r.direction());
     auto t = 0.5 * (unit_direction.y() + 1.0);
@@ -21,10 +26,11 @@ Color ray_color(const Ray& r, const Hittable& world) {
 
 int main() {
     const auto aspect_ratio = 16.0 / 9.0;
-    const int image_width = 1280;
-    //const int image_width = 384;
+    //const int image_width = 1280;
+    const int image_width = 384;
     const int image_height = static_cast<int>(image_width / aspect_ratio);
-    const int samples_per_pixel = 100;
+    const int samples_per_pixel = 250;
+    const int max_depth = 50;
 
     std::cout << "P3\n" << image_width << " " << image_height << "\n255\n";
 
@@ -39,10 +45,10 @@ int main() {
         for (int i = 0; i < image_width; ++i) {
             Color pixel_color(0, 0, 0);
             for (int s = 0; s<samples_per_pixel; ++s) {
-                auto u = double(i + random_double()) / (image_width - 1);
-                auto v = double(j + random_double()) / (image_height - 1);
+                auto u = double(i + random_double(-0.5, 0.5)) / (image_width - 1);
+                auto v = double(j + random_double(-0.5, 0.5)) / (image_height - 1);
                 Ray r = cam.get_ray(u, v);
-                pixel_color += ray_color(r, world);
+                pixel_color += ray_color(r, world, max_depth);
             }
             write_color(std::cout, pixel_color, samples_per_pixel);
         }