From 3deef4d969dd50ddf540b80fe43ef16af5c17169 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Mon, 24 Jun 2024 22:51:51 +0100
Subject: Chapter 11

---
 vec3.go | 9 +++++++++
 1 file changed, 9 insertions(+)

(limited to 'vec3.go')

diff --git a/vec3.go b/vec3.go
index a540b7c..f590625 100644
--- a/vec3.go
+++ b/vec3.go
@@ -95,3 +95,12 @@ func RandomVec3OnUnitSphere() (v Vec3) {
 func (v Vec3) Reflect(n Vec3) Vec3 {
   return v.Sub(SplatVec3(2 * v.Dot(n)).Mul(n));
 }
+
+func (v Vec3) Refract(n Vec3, eta_ratio float64) Vec3 {
+  cos_theta := maths.Min(v.Neg().Dot(n), 1.0);
+  r_out_perp := SplatVec3(eta_ratio).
+               Mul(v.Add(SplatVec3(cos_theta).Mul(n)));
+  rops := -maths.Sqrt(maths.Abs(1.0 - r_out_perp.MagSqr()));
+  r_out_parr := SplatVec3(rops).Mul(n);
+  return r_out_perp.Add(r_out_parr);
+}
-- 
cgit v1.2.1