DescriptorMatcher::add method (http://docs.opencv.org/modules/features2d/doc/common_interfaces_of_descriptor_matchers.html#descriptormatcher-add) wants a vector of matrices with descriptors. So, even if I want to train matcher for only one image (object), I have to create a dummy vector, put my descriptors there and give this vector to the DescriptorMatcher.
Is there an elegant way to add descriptors without a temporary vector?