/// make sure it has at least 3 elements
explicit SGVec3(const T* d)
{ data()[0] = d[0]; data()[1] = d[1]; data()[2] = d[2]; }
+ template<typename S>
+ explicit SGVec3(const SGVec3<S>& d)
+ { data()[0] = d[0]; data()[1] = d[1]; data()[2] = d[2]; }
explicit SGVec3(const osg::Vec3f& d)
{ data()[0] = d[0]; data()[1] = d[1]; data()[2] = d[2]; }
explicit SGVec3(const osg::Vec3d& d)