From 3c1610c55889e3169142d2af1eece43c63022672 Mon Sep 17 00:00:00 2001
From: dooglus <dooglus@1f10aa63-cdf2-0310-b900-c93c546f37ac>
Date: Tue, 4 Mar 2008 22:02:22 +0000
Subject: [PATCH] Improve the derivative class for hermites.  Compare
 http://synfig.org/images/a/a8/Bline-tangent-inaccuracy-before.png and
 http://synfig.org/images/a/a7/Bline-tangent-inaccuracy-after.png, the results
 of rendering http://synfig.org/images/b/bd/Bline-tangent-inaccuracy.sifz .

git-svn-id: http://svn.voria.com/code@1857 1f10aa63-cdf2-0310-b900-c93c546f37ac
---
 ETL/trunk/ETL/_calculus.h                              | 18 ++++++++++++++++++
 .../trunk/src/synfig/valuenode_blinecalctangent.cpp    |  2 +-
 .../trunk/src/synfig/valuenode_segcalctangent.cpp      |  2 +-
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/ETL/trunk/ETL/_calculus.h b/ETL/trunk/ETL/_calculus.h
index 279ed91..9fbea85 100644
--- a/ETL/trunk/ETL/_calculus.h
+++ b/ETL/trunk/ETL/_calculus.h
@@ -28,6 +28,8 @@
 
 #include <functional>
 
+#include "hermite"
+
 /* === M A C R O S ========================================================= */
 
 //#ifndef _EPSILON
@@ -56,6 +58,22 @@ public:
 };
 
 template <typename T>
+class derivative<hermite<T> > : public std::unary_function<typename hermite<T>::argument_type,typename hermite<T>::result_type>
+{
+	hermite<T> func;
+public:
+	explicit derivative(const hermite<T> &x):func(x) { }
+
+	typename hermite<T>::result_type
+	operator()(const typename hermite<T>::argument_type &x)const
+	{
+		T a = func[0], b = func[1], c = func[2], d = func[3];
+		typename hermite<T>::argument_type y(1-x);
+		return ((b-a)*y*y + (c-b)*x*y*2 + (d-c)*x*x) * 3;
+	}
+};
+
+template <typename T>
 class integral : public std::binary_function<typename T::argument_type,typename T::argument_type,typename T::result_type>
 {
 	T func;
diff --git a/synfig-core/trunk/src/synfig/valuenode_blinecalctangent.cpp b/synfig-core/trunk/src/synfig/valuenode_blinecalctangent.cpp
index 50c3afc..0d27157 100644
--- a/synfig-core/trunk/src/synfig/valuenode_blinecalctangent.cpp
+++ b/synfig-core/trunk/src/synfig/valuenode_blinecalctangent.cpp
@@ -125,7 +125,7 @@ ValueNode_BLineCalcTangent::operator()(Time t)const
 
 	etl::hermite<Vector> curve(blinepoint0.get_vertex(),   blinepoint1.get_vertex(),
 							   blinepoint0.get_tangent2(), blinepoint1.get_tangent1());
-	etl::derivative< etl::hermite<Vector> > deriv(curve, 0.0001);
+	etl::derivative< etl::hermite<Vector> > deriv(curve);
 
 	switch (get_type())
 	{
diff --git a/synfig-core/trunk/src/synfig/valuenode_segcalctangent.cpp b/synfig-core/trunk/src/synfig/valuenode_segcalctangent.cpp
index e27d950..a4b735c 100644
--- a/synfig-core/trunk/src/synfig/valuenode_segcalctangent.cpp
+++ b/synfig-core/trunk/src/synfig/valuenode_segcalctangent.cpp
@@ -82,7 +82,7 @@ ValueNode_SegCalcTangent::operator()(Time t)const
 	Segment segment((*segment_)(t).get(Segment()));
 
 	etl::hermite<Vector> curve(segment.p1,segment.p2,segment.t1,segment.t2);
-	etl::derivative< etl::hermite<Vector> > deriv(curve, 0.0001);
+	etl::derivative< etl::hermite<Vector> > deriv(curve);
 
 	return deriv((*amount_)(t).get(Real()));
 }
-- 
2.7.4