From 267df23c87d02da419951a04021b44570e803e3b Mon Sep 17 00:00:00 2001
From: Faerbit <faerbit@gmail.com>
Date: Sat, 6 Jun 2020 16:16:31 +0200
Subject: [PATCH] Add additional scattering methods.

---
 Makefile    |  2 +-
 vec3.h      | 15 +++++++++++++++
 wtracer.cpp |  8 +++++---
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index cc4f0df..283401a 100644
--- a/Makefile
+++ b/Makefile
@@ -10,7 +10,7 @@ TARGET = wtracer
 all: $(TARGET) run
 
 run:
-	./wtracer > image.ppm
+	time -f '%E elapsed' ./wtracer > image.ppm
 	eog image.ppm
 
 %.o: %.cpp $(DEPS)
diff --git a/vec3.h b/vec3.h
index df7f98b..92f42ea 100644
--- a/vec3.h
+++ b/vec3.h
@@ -120,4 +120,19 @@ Vec3 random_in_unit_sphere() {
     }
 }
 
+Vec3 random_unit_vector() {
+    auto a = random_double(0, 2*pi);
+    auto z = random_double(-1, 1);
+    auto r = std::sqrt(1 - z*z);
+    return Vec3(r*std::cos(a), r*std::sin(a), z);
+}
+
+Vec3 random_in_hemisphere(const Vec3& normal) {
+    Vec3 in_unit_sphere = random_in_unit_sphere();
+    if (dot(in_unit_sphere, normal) > 0.0)
+        return in_unit_sphere;
+    else
+        return -in_unit_sphere;
+}
+
 #endif  // VEC3_H
diff --git a/wtracer.cpp b/wtracer.cpp
index f21d0ad..d197041 100644
--- a/wtracer.cpp
+++ b/wtracer.cpp
@@ -15,8 +15,10 @@ Color ray_color(const Ray& r, const Hittable& world, int depth) {
     if (depth <= 0)
         return Color(0, 0, 0);
 
-    if (world.hit(r, 0, infinity, rec)) {
-        Point3 target = rec.p + rec.normal + random_in_unit_sphere();
+    if (world.hit(r, 0.001, infinity, rec)) {
+        //Point3 target = rec.p + rec.normal + random_in_unit_sphere();
+        //Point3 target = rec.p + rec.normal + random_unit_vector();
+        Point3 target = rec.p + random_in_hemisphere(rec.normal);
         return 0.5 * ray_color(Ray(rec.p, target - rec.p), world, depth-1);
     }
     Vec3 unit_direction = unit_vector(r.direction());
@@ -30,7 +32,7 @@ int main() {
     const int image_width = 768;
     //const int image_width = 384;
     const int image_height = static_cast<int>(image_width / aspect_ratio);
-    const int samples_per_pixel = 250;
+    const int samples_per_pixel = 400;
     const int max_depth = 50;
 
     std::cout << "P3\n" << image_width << " " << image_height << "\n255\n";