From c4eb43a6f3fd5bfd9a5ad68fbe7fc87a3744d24b Mon Sep 17 00:00:00 2001
From: K Tyl <me@ktyl.dev>
Date: Thu, 4 Jun 2020 00:47:33 +0100
Subject: [PATCH] linear interpolation for vectors

---
 src/main.cpp | 6 +++++-
 src/vec3.h   | 5 +++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/main.cpp b/src/main.cpp
index bcdf74c..5c5ff72 100755
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -12,7 +12,11 @@ colour rayColour(const ray& r)
 {
     vec3 unitDirection = unitVector(r.direction());
     double t = 0.5 * (unitDirection.y() + 1.0);
-    return (1.0-t) * colour(1.0,1.0,1.0) + t*colour(0.5, 0.7, 1.0);
+
+    auto a = colour(1.0, 1.0, 1.0);
+    auto b = colour(0.0, 0.0, 0.0);
+
+    return lerp(a, b, t);
 }
 
 int main()
diff --git a/src/vec3.h b/src/vec3.h
index 5045353..08d3f46 100755
--- a/src/vec3.h
+++ b/src/vec3.h
@@ -107,6 +107,11 @@ inline vec3 cross(const vec3 &u, const vec3 &v)
                 u.e[0] * v.e[1] - u.e[1] * v.e[0]);
 }
 
+inline vec3 lerp(const vec3 &a, const vec3 &b, double t)
+{
+    return (1.0 - t) * a + t * b;
+}
+
 inline vec3 unitVector(vec3 v)
 {
     return v / v.length();