From d49e7d03007add0da079ddad0a338b0484d61b08 Mon Sep 17 00:00:00 2001
From: Moritz Gmeiner <moritz@gmeiner.net>
Date: Sun, 31 Dec 2023 13:47:03 +0100
Subject: [PATCH] fixed reflectance in Dielectric

---
 src/material.h | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/material.h b/src/material.h
index c8fe960..84dd607 100644
--- a/src/material.h
+++ b/src/material.h
@@ -86,17 +86,18 @@ class Dielectric : public Material {
 
         Vec3 out_dir;
 
+        // Schlick approximation
         constexpr auto reflectance = [](f64 cos, f64 eta) {
-            auto r0 = (1 - eta) / (1 + eta);
-            r0 = r0 * r0;
-            return r0 * (1 - r0) * std::pow(1 - cos, 5);
+            auto r = (1 - eta) / (1 + eta);
+            f64 r2 = r * r;
+            return r2 + (1 - r2) * std::pow(1 - cos, 5);
         };
 
         if (eta * sin_theta > 1.0 || reflectance(cos_theta, eta) > rand.GenUniform()) {
-            // can't refract, must reflect or Schlick approximation
+            // reflect
             out_dir = in.direction().reflect(hit_record.normal);
         } else {
-            // reflect
+            // refract
             out_dir = in.direction().refract(hit_record.normal, eta);
         }