Hello to all, I want to apply to geometrical transformations (in this case translations) on a point. Point3D trans1(1,0,0); Point3D trans2(2,0,0); Point2D p(100,100); gtl::transformation<int> T1( trans1 ); gtl::transformation<int> T2( trans2 ); gtl::transform( p, T1 ); gtl::transform( p, T2 ); --- ... and the point's coordinates are (97,100) as expected. --- When I try to concatenate the transformations: Point3D trans1(1,0,0); Point3D trans2(2,0,0); Point2D p(100,100); gtl::transformation<int> T1( trans1 ); gtl::transformation<int> T2( trans2 ); gtl::transform( p, T1 + T2 ); --- ... and I get random numbers. I checked the boost/polygon/detail/transform_detail.hpp template <typename coordinate_type> inline const transformation<coordinate_type>& transformation<coordinate_type>::operator+=(const transformation<coordinate_type>& tr){ //apply the inverse transformation of this to the translation point of that //and convolve it with this translation point coordinate_type x, y, z; transformation<coordinate_type> inv = inverse(); inv.transform(x, y, z); p_.set(HORIZONTAL, p_.get(HORIZONTAL) + x); p_.set(VERTICAL, p_.get(VERTICAL) + y); p_.set(PROXIMAL, p_.get(PROXIMAL) + z); //concatenate axis transforms atr_ += tr.atr_; return *this; } ... and I noticed that the coordinate_type x, y, z; is not initialized and then the transformation is applied: inv.transform(x,y,z); which of course results to something random. Any ideas? Thank you for checking. Dimitris