From 44f218988cab042d2db6eba2e22e6d651d4d5fd2 Mon Sep 17 00:00:00 2001 From: Gael Guennebaud Date: Sun, 8 Mar 2009 11:38:45 +0000 Subject: [PATCH] add a small note in Transform doc. --- Eigen/src/Geometry/Transform.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/Eigen/src/Geometry/Transform.h b/Eigen/src/Geometry/Transform.h index 8b5e9619c..2977a63ee 100644 --- a/Eigen/src/Geometry/Transform.h +++ b/Eigen/src/Geometry/Transform.h @@ -139,6 +139,15 @@ template struct ei_transform_transform_product_impl; * that case the last matrix row can be ignored, and the product returns non * homogeneous vectors. * + * Since, for instance, a Dim x Dim matrix is interpreted as a linear transformation, + * it is not possible to directly transform Dim vectors stored in a Dim x Dim matrix. + * The solution is either to use a Dim x Dynamic matrix or explicitely request a + * vector transformation by making the vector homogeneous: + * \code + * m' = T * m.colwise().homogeneous(); + * \endcode + * Note that there is zero overhead. + * * Conversion methods from/to Qt's QMatrix and QTransform are available if the * preprocessor token EIGEN_QT_SUPPORT is defined. *