From ebf906a23a9c4a92f8ea3a8b783f0070ae3f87f3 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Fri, 19 Dec 2008 16:31:22 +0000
Subject: [PATCH] add matrix * transform product

---
 Eigen/src/Geometry/Transform.h | 7 +++++++
 test/geometry.cpp              | 7 ++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/Eigen/src/Geometry/Transform.h b/Eigen/src/Geometry/Transform.h
index 5d7f610cb..d62a9c98d 100644
--- a/Eigen/src/Geometry/Transform.h
+++ b/Eigen/src/Geometry/Transform.h
@@ -184,6 +184,13 @@ public:
   operator * (const MatrixBase<OtherDerived> &other) const
   { return ei_transform_product_impl<OtherDerived,Dim,HDim>::run(*this,other.derived()); }
 
+  /** \returns the product expression of a transformation matrix \a a times a transform \a b
+    * The transformation matrix \a a must have a Dim+1 x Dim+1 sizes. */
+  template<typename OtherDerived>
+  friend inline const typename ProductReturnType<OtherDerived,MatrixType>::Type
+  operator * (const MatrixBase<OtherDerived> &a, const Transform &b)
+  { return a.derived() * b.matrix(); }
+
   /** Contatenates two transformations */
   inline const Transform
   operator * (const Transform& other) const
diff --git a/test/geometry.cpp b/test/geometry.cpp
index 9885380ca..8c0d3b688 100644
--- a/test/geometry.cpp
+++ b/test/geometry.cpp
@@ -180,7 +180,7 @@ template<typename Scalar> void geometry(void)
   VERIFY_IS_APPROX(t0.prescale(a).matrix(), t1.prescale(Vector3::Constant(a)).matrix());
 
   // More transform constructors, operator=, operator*=
-  
+
   Scalar a3 = ei_random<Scalar>(-M_PI, M_PI);
   Vector3 v3 = Vector3::Random().normalized();
   AngleAxisx aa3(a3, v3);
@@ -212,6 +212,9 @@ template<typename Scalar> void geometry(void)
   t4 *= sv3;
   VERIFY_IS_APPROX(t6.matrix(), t4.matrix());
 
+  // matrix * transform
+  VERIFY_IS_APPROX(Transform3(t3.matrix()*t4).matrix(), Transform3(t3*t4).matrix());
+
   // chained Transform product
   VERIFY_IS_APPROX(((t3*t4)*t5).matrix(), (t3*(t4*t5)).matrix());
 
@@ -220,8 +223,6 @@ template<typename Scalar> void geometry(void)
   t5 = t5*t5;
   VERIFY_IS_APPROX(t5, t4*t4);
 
-
-
   // 2D transformation
   Transform2 t20, t21;
   Vector2 v20 = Vector2::Random();