From 6305261270b6e2dcada76dad057b1cd953e4ac4d Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Thu, 17 May 2012 14:17:42 +1000
Subject: [PATCH] Add trun, cubic, and quintic lerp methods

---
 lerp.cpp | 18 ++++++++++++++++++
 lerp.hpp |  7 +++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/lerp.cpp b/lerp.cpp
index a8e89b56..d50b1de8 100644
--- a/lerp.cpp
+++ b/lerp.cpp
@@ -31,6 +31,10 @@ lerp::sigmoid (double val) {
 }
 
 
+double lerp::trunc (double a, double, double)
+    { return a; }
+
+
 double
 lerp::linear (double a, double b, double weight) {
     CHECK (weight >= 0 && weight <= 1.0);
@@ -47,3 +51,17 @@ lerp::cosine (double a, double b, double weight) {
     return a * (1.0 - f) + b * f;
 }
 
+
+double
+lerp::cubic (double a, double b, double weight) {
+    CHECK (weight >= 0.0 && weight <= 1.0);
+    double t = weight * weight * (3.0 - 2.0 * weight);
+    return a * (1.0 - t) + b * t;
+}
+
+
+double
+lerp::quintic (double a, double b, double weight) {
+    double t = weight * weight * weight * (weight * (weight * 6.0 - 15.0) + 10.0);
+    return a * (1.0 - t) + b * t;
+}
diff --git a/lerp.hpp b/lerp.hpp
index 7bfd2a3e..88384874 100644
--- a/lerp.hpp
+++ b/lerp.hpp
@@ -23,8 +23,11 @@
 namespace lerp {
     double sigmoid (double val);
 
-    double linear (double a, double b, double weight);
-    double cosine (double a, double b, double weight);
+    double linear  (double a, double b, double weight);
+    double cosine  (double a, double b, double weight);
+    double cubic   (double a, double b, double weight);
+    double quintic (double a, double b, double weight);
+    double trunc   (double a, double b, double weight);
 }
 
 #endif